[Anne] Good evening everyone. Welcome to the Cornell Lab of Ornithology. My name is Anne Rosenberg and I am the coordinator of public programs here at the lab and I especially want to welcome you to our Monday night seminar series, which has been going on for decades, actually, ever since it was started by the lab’s founder Arthur Allen. And it’s been a real tradition ever since.

I have never introduced the program so I have a little piece of paper to help me out. But tonight’s program is a special one. We have not one but three… one minute. I think … can you press the red button? It’s a big. It looks like it would be scary but just push it. I did it though, so don’t hit it again.

Okay so we’re starting over. So this evening’s program is a particularly special one. We have three, not one, but three distinguished researchers who will be talking to us this evening about their their research.

They are all three, they hold the Edward Rose postdoctoral fellows here at the lab, which is something that attracts some of the best young researchers from around the world actually. So all three of them are part of the Edward Rose postdoctoral fellowship. Tonight’s speakers are Cecilia Nilsson, Kyle Horton, and Adriaan Dokter, and they’re part of a new and growing and very exciting field of study which is called radar ornithology.

And in this they use radar to study the bird migration in new ways that we never would have even imagined before. And some of you have heard of some of the the studies that have gone on with night migration in the recent years. I think I remember very vividly when I first was told that the what was called what the weather people call noise and just you know nothing up on the radar screens was actually maybe birds. So you’re gonna hear a lot more about that this evening and that turned out to be the beginning of a very exciting new area of study.

So the first one to speak will be Cecilia Nilsson and each one of them will tell you more about themselves as they share with you the research that they’ve been working on. Thanks.


[Cecilia] Thank you, Anne. Um so hey, yeah my name is Cecilia Nilsson and as Anne said I’m a postdoc here, and I’m really excited to be here today to talk about how we use radar to study flight behavior of nocturnal migrants. And my background is that I did my PhD in Lund. I’m from Sweden originally so I did my PhD there at Lund University where I studied nocturnal songbirds with radar. The radar in the picture here actually.

[Slide text: Using radar to study songbird flight behavior, Cecilia Nilsson, Cornell Lab of Ornithology]

And then I did a first postdoc in Switzerland and now I’m here for my second postdoc. So I’m really happy to be here to talk a little bit about this.

[Slide text: Songbird migration; Photo: geese flying overhead in a v pattern]

Okay, so as I said, I study songbird migration and their flight behavior. But of course that isn’t really as easy as it might sound because, if you look at this picture, you’re gonna see something is a bit wrong here, right. So I say songbird migration, but this is of course not songbirds migrating because this is not what it looks like when songbirds migrate.

[Slide text: Songbird migration with blank black screen]

When songbird, songbirds migrate it looks like this because most songbirds migrate during the night at high altitudes, so it’s very hard to observe it directly, right. So yeah, so that’s why it’s great that we have different technologies to help us with this.

[Slide text: Angels?

-Angels during WW2

-David Lack- RADAR echoes from birds

-“See” birds far away, high up, also at night

Photos: Early radar in use]

And one of the great technologies that we have is radar, and so radar was invented during the Second World War, and almost instantly they realized that they were seeing something on the radar screens that they couldn’t describe. And since radar operators during that time apparently were a bit dramatic, they call them angels.

And because these were things that weren’t man-made, they were too small, but they weren’t moving with the wind so they couldn’t understand what was going on. So luckily there were people that didn’t believe so much in the paranormal, such as the famous ornithologist David Lack who was one of the first people to actually identify this as being bird echoes that they could see on the radar.

So now we have a method to be able to see birds also when they’re far away and during the night and at high altitudes. So that was the beginning, but then, and then radar ornithology continued, and there were some studies done. But now there’s really, as Anne said, been a new revival in this because we have new methods, new technology, but also above all new, much more computer power to actually be able to analyze these images in a much better way that means that we can do research in a way that hasn’t been possible before.

[Slide text: Radar types; Photos: two types of radar]

And there are many different kinds of radars, of course. And there are mainly two types that we use in radar ornithology. There’s, first there’s the more small-scale, local bird radars that are adapted to actually follow birds and are slightly different, as the tracking radar you can see on your left here.

And then we have the big continent wild, wide weather radar networks, such as the one on the right. And Adriaan and Kyle will tell you more about what we do with the weather radars, I’m gonna talk a little bit more about data from the local scale radars now first.

[Animation of radar emitting signal and reflecting off a bird before bouncing back]

So how does a radar work? Well, it’s quite simple. It emits a signal and then it measures when the signal comes back. And it, the signal reflects out of many different, reflects on many different things. It can reflect the metal so that’s how we can track airplanes and things like that, but it also reflects from water so that’s how weather radars work and how they can track precipitation and storms and things like that.

And then of course a bird body is mainly water, so it also reflects from birds and other biological tissue. And this is of course great news for us, because that means that we now have a way to track free flying birds without having to handle or tag them in any way. We can just track them passively while they’re flying above us.

[Photo: Woman sitting in front of control panel]

And this is what it kind of what it can look like when you’re a radar ornithologist. This is the control panel of our tracking radar. And with this we can then get very exact measurements of the birds’ flight speed, flight directions, altitude, and exact position where they are. And with some radars you can also get an intensity measure, so how many birds there actually are up in the air at the same time.

So as I said, this is a picture of our radar dashboard, but it’s actually also a picture of a bird. Do you see the bird? It’s maybe not so nice, maybe if I do this. Do you see it now?

[Photo: Previous photo zoomed in on radar screen, with one area circled in red]

So this is actually you can say a representation of the radar signal, and you can see the signal is being interrupted there by the echo. And the echo is changing in strength as the bird’s area is changing when it’s beating its wings. So when it’s beating its wings its area expands and retracts. How much, how strong the signal reflecting back is.

So then the next question might be, I guess most of you here are bird watchers or so, so what species is this?


You want to guess?

It could be a swift. It’s not a swift. It could actually be a swift, but yeah even for a radar ornithologist it’s not that easy. So that was actually the point. We don’t know, I don’t know what species this is because we can’t separate species with the radar. We can if we have wingbeat frequencies like in this case, we can kind of say something about the broad groups and swift is a good example because that’s one of the species that have a very special wing beat frequency, and therefore we can usually identify them. But otherwise we’re left at trying to figure out what we’re looking at more based on the timing and the area and so on, so we have to use other data sources to say something about species.

[Slide text: Flight behavior; Image: bird with airspeed, heading, wind speed, wind direction, ground speed, and track direction labeled]

Okay so my main study area is flight behavior and just some basic concepts. A bird that’s flying of course, it has its own airspeed and it has its own heading. And that’s just the speed with which it’s flying, so how fast it’s flapping its wings, and the heading is how its body is directed in the air. But then of course a bird flying is not like us walking around or something like that because it’s moving in a medium that is moving itself, right. So we have to add the wind speed and the wind direction to be able to know or to get at how the bird is actually moving over ground. So the speed with which the bird is moving over ground is a function of both its own propulsion and the wind effect on it. And the direction it’s flying in as well.

[Slide text: Optimal migration theory

Minimizing time spent on migration

Minimizing energy spent on migration

Graph: Rate of Fuel Depletion, speed versus power. A slight U shape]

And you don’t have to be too terrified now by this graph, which it might look a bit daunting. But it’s just there to show that we also have a lot of theory behind this, and how we have different predictions of how birds should optimally migrate. And depending on how they behave, or we can use different aspects of their behavior to try to figure out what is the currency that they use during their migration and what if they are constrained by.

And mainly we’re interested in different behaviors that indicate that their time-minimizing or that they’re stressed and that they want to get there as fast as possible. Or in the other hand they could be energy-minimizing so that they’re just trying to preserve as much energy as possible where time is not as important.

And this leads to all sorts of different predictions of how they should behave and one of the predictions that is central to that is that they should use different flight speeds for these different behaviors. So a bird that is more interested in getting there fast will fly slightly faster than a bird that’s more interested in getting there with as little as little energy loss as possible.

[Slide text: Flight speed

Faster spring than fall

Graph: Sites versus Airspeed, showing Autumn and Spring]

So we tracked a lot of birds with our radar and we measured a lot, a lot of flights, flight speeds at different places and during different years. And one of the things that we can see consistently was that flight speeds during spring were almost always higher than flight speeds during autumn, which was interesting. And we wanted to look at this also over, see if this was a general pattern and not just in our data. So we looked at a bunch of different studies that all had measured flight speed or different aspects of migration speed in both spring and autumn. And then we calculated a ratio between spring and autumn, so on the graphs that are going to come up here they’re all going to be positive when it’s a faster spring and negative when it’s a faster autumn migration.

[Slide text: Flight speed

Ratio between spring and fall speed

Spring migration generally faster than fall migration

Graphs: Airspeed, General speed, Travel speed, Stop-over duration, Total migration speed, Total duration]

And we saw a pretty convincing pattern that in almost all cases and almost all studies that we looked into spring was faster than autumn. And we thought that this is really interesting because the difference there also matches quite well with what we would predict between being time stressed and being energy stressed. So one possible explanation for this is that they simply are more time stressed during spring migration when they’re getting to the breeding grounds than they are during autumn migration when they might be more interested in conserving energy and getting to the wintering grounds.

Okay and then that other aspect that a little trying all the velocities that I showed you was of course the wind and… yeah?

Yeah so the question was if there would be a difference between young birds and adults because the autumn sample will consist of more young birds. That’s true absolutely. That might be an aspect of it. We don’t think so, and we’ve tried to control for it in different ways, and we’ve measured flight speeds of adults and juveniles without seeing a difference. But there might still be some, some of that, yeah.

[Slide text: Wind assistance? Photo: bird taking flight off a branch; Graph: Wind effect versus number of birds]

Yeah so the other aspect of this of course is then the wind speed. And a small passerine or songbird like this can fly with about 12 meters per second of their own propulsion. And so you can understand that if they have a really good tailwind they can almost fly double the speed over ground, and with a bad headwind they could almost make no headway at all over ground, right.

So one of the things we look at is in what wind situations do they actually fly. So when we look at our individual data we see that, well it’s not the case that they only flying these really good tailwind situation. so tail winds here are in blue and headwinds are in red. but in actually rather a lot of cases they have to fly in headwind situations.

[Slide text: Wind assistance; Image: United States map with wind direction arrows, photo of radar; Graph: Wind effect versus number of birds]

And that’s one of the things that we also looked at with the larger weather radar data set. So instead of the hundreds of individuals I showed you on this formal graph, we’re now looking at all 143 sites and 25 years of data. So each point in this graph represents several thousand birds.

And you can see again that it’s not the case that they’re only flying in very good winds, they’re flying in all sorts of winds. And of course that’s a function of the fact that there aren’t that many winds to choose from, so what we need to look at is how selective of, are they of what wind situations they fly in. And then we can again come back to the theories about optimal migration, which predicts that birds that are very time constrained will be less selective and flying more wind situations, different wind situations while birds that are more energy constrained would rather sit and wait for really good wind situation.

Okay and now I just want to show, share a little short story that I think kind of combines both these flight speed and wind aspects and also shows you that you can look at other things, not only birds with radar.

[Slide text: Not only birds; Photos: two radars, one with a moth next to it and one with a bird next to it]

So also insects show up really nicely on radar and there are special insect-dedicated radars are just one on the picture here. And then of course we’re not that many people in the world that actually worked with biological radar data collection. It’s basically us in the room and a few more so we know each other pretty well.

[Slide text: As fast migrants? Graph: moth and bird spring and autumn migration ground speed]

So of course you start to discuss and then these insect people are saying that well our moths are flying as fast as your birds. Yeah right, no. Don’t think so, that seems kind of unlikely. But yeah they were adamant, no our nocturnal moths can fly as fast as your birds. Okay so we said okay let’s look at the data. And we were wrong. They could actually fly as fast as our birds.

[Slide text: Moth Slow flyers ~4 m/s Strong wind selectivity Downward orientation; Bird Fast flyers ~12 m/s Weak wind selectivity Goal orientation; Similar ground speeds and Similar track directions]

So when we look at the ground speed you can see that they almost completely overlapped between their nocturnal moths and the nocturnal migrants or nocturnal songbirds. Which was a pretty big surprise because that’s not at all what you would expect, right? So what’s going on here. Well, we have moths and we know that most can only fly at about four meters per second with their own self-propulsion, so their airspeed is only four meters per second or something like that. And we have the passerines that we know can fly with about twelve meters per second. But then the difference is that they show very different behavior in relation to this wind selectivity that we were just talking about. So the moths are actually very strongly wind selective and only fly on very, very good nights while the bird as we saw before fly in a variety of nights. So in the end this actually leads to the moths getting so much wind assistance that they achieve similar ground speeds as the birds, And in the same way the moths are also orienting downwind with the wind so they’re choosing the wind situations where the wind is blowing exactly where they want to go. While the birds are orienting towards the goal where they want to fly, not where the wind is blowing. and in the end they also achieve similar track directions.

So I think this is a nice story of how two organisms with very different life histories and very different abilities use their behaviors to actually achieve similar results in the end.

[Photo: Sunset with birds flying through the sky]

So that was the parts about flight behavior I wanted to share and now Kyle is going to talk a little bit about how we use weather radars to forecast migration.


[Slide text: Cloudy with a chance of migration, Kyle Horton, @kyle_horton, The Cornell Lab of Ornithology]

[Kyle] Thanks everyone, can you hear me okay? Okay my name is Kyle Horton and as Anne said I’m a postdoc here at the Lab of Ornithology. I did my PhD at the University of Oklahoma so I’m traveling a bit as well but not as far as sort of Adriaan and Cecilia. Before I start just to sort of give you a road map of where I’m going, I’m using weather surveillance radar. And I’ll give you sort of a primer on that as well. But I’m using in a way during this talk of trying to understand how birds are interacting with a changing landscape and that changing landscape being the medium that these birds are going through, the airspace and how it’s changing, and some novel stimuli that these birds may be seeing, and then trying to motivate that work to actually make predictive forecasts into the future of you know, can we actually say with reasonable confidence of where these birds will go and where they’re coming from and where we predict them to be in the airspace.

[Slide text: Acknowledgements: Benjamin Van Doren- University of Oxford

Andrew Farnsworth- Cornell Lab of Ornithology]

Before I sort of jump into it I just wanted to put acknowledgments up front of folks that have sort of been instrumental to some of this work. I’ve worked with Andrew Farnsworth and Benjamin Van Doren here for over five years now and some of this work and sort of both or have been quite avid in the this world of radar ornithology so I just wanted to sort of front-load that.

[Photo: Hooded Warbler on the ground]

And I’ll just sort of jump into you know my passion of of using weather smelts radar to understand you know these beautiful birds.

[Photo: Painted Bunting perched in tree]

[Photo: Whimbrel in flight]

And I’ve been quite interested in birds and especially migratory birds, you know the the variation that we see in these in these species and you know they’re not only their plumage but their behavior as Cecilia was talking about, and where these birds are coming from and where they’re going is quite diverse.

[Photo: Chestnut-sided Warbler perched on the end of a branch]

[Photo: Swainson’s Thrush perched on a tree]

[Photo: Scarlet Tanager with fruit in its beak]

[Slide text: Life on the move… in the dark, About 19% of bird species are identified as migratory; Photos: various birds]

And migration itself is sort of not an uncommon trait in avian communities. about 19 percent of known bird species are considered migratory in some capacity.

Some of those are short distance migrants, some are longer, some are elevational migrants but as I said that’s a significant portion of the the avian sort of avifauna across the world. And especially in North America, most of them actually move at night and that’s probably pretty obvious to this community of bird watchers, but if not that’s sort of one thing to always take away when you sort of talking about birds is that most of them, especially the songbirds, are moving under the cover of darkness as Cecilia talked about.

[Photo: Forest and blue sky]

And these birds are moving through airspace they’re you know we sort of envision that they’re they’re moving through this pristine habitat you know going across landscapes that look like this and using the Stars to navigate and maybe following local topography to sort of navigate.

[Photo: New York City]

But the reality is is that most migrants are probably seeing habitats that look like this. And this is sort of on the extreme of that spectrum, right, this is you know lower Manhattan, New York City. And we know that birds are flying over this this airspace as well.

[Photo: Central Park]

You know the great example of the Central Park effect of how many birds funnel into this habitat. Lots, yeah. And we know they’re making landfall there but they’re making landfall in this area when it looks like this.

[Photo: New York City at night]

So anthropogenic light, artificial light, at night is a fairly novel stimuli for these birds. In terms of you know thinking about the evolution of these migrants and how long they’ve been sort of using these migratory routes. So understanding how these birds are interacting with this novel stimulus and trying to sort of make sense of you know is it changing the behavior of these migrants.

I’ve been fortunate enough to work on a project through the Lab of Ornithology and also in conjunction with the National Audubon Society and New York City, and I’m sure this this sort of light source is quite familiar to most in the room.

[Photo: Lights of the September 11th tribute]

But this is the September 11th tribute in light that goes on every September. And this is sort of an interesting study for many many reasons.

You know lower Manhattan is heavily photo polluted all times of the year at night but on this one night we sort of have an additional stimulus. So are migrants actually attracted to this one light source when there’s this continuous glow?

[Video: View from under the lights, with birds flying by]

And this is actually a video I took last September. This is me sitting below one of those those beams of light the one of two so each beam is actually made up of 44 individual lights and that’s sort of the streamers you see shooting up in an airspace here.

So what look like insects here are actually migratory birds. And these migratory birds are largely composed of wood warblers, these colorful you know birds that you know attract so many bird watchers and they’re sort of so exciting during the spring migration period. So on this night it was really dominated by things like American redstarts, yellow warblers, northern parula. so just a tremendous amount of birds circling and attracted to these lights it’s very clear that it’s changing their behavior.

It’s not only their flight behavior they seem to be disoriented. They call and frequently flight call. So there’s sort of this cacophony of flight calls going on during this event as well. And it’s not sort of all doom and gloom in this regard as well. And that the folks that organized this tribute are aware that they don’t want to see thousands of dead birds at this site. So through the monitoring and the partnership with the Lab of Ornithology, the New York City Audubon, folks monitor these lights all night. And once a thousand birds are detected in this beam of light they’ll actually turn them off for twenty minutes.

And the birds very clearly sort of go on their migratory journey. But it’s just sort of one example of how lights at night are changing behaviors of birds. So can we begin to understand where these greatest threats are especially across the US. Yep? Yeah so it’s, the question was what is the policy or before this this threshold is hit, sort of what was going on before this? And it really sort of started right from the beginning. it was very obvious sort of once the lights even during this sort of the testbed of the lights  that migrants are being attracted. And I don’t recall exactly when the policy was sort of you know set in place, but it was very quick from the onset. It probably was in 2003 but I can check on that. But it was sort of right from the get-go and they haven’t seen you know tremendous mortality in any regard.

And each year isn’t sort of the same migration pace as well. Some years we really don’t see a lot of birds just because the birds aren’t in the airspace on a given night. So there is sort of variation of it as well.

[Photo: New York City area at night from space]

So this is actually a New York City or the Greater New York City area from space. So and this is a NASA satellite that measures light reflectance from space. And New York City obviously sort of isn’t a unique case in terms of photo pollution. So this is sort of one of many cities across the United States that are heavy photo polluters.

[Photo: Each of the 125 largest U.S. cities at night from space]

So I’ve been working on a study in conjunction with Adriaan and Cecilia here, of trying to quantify this impact across you know urban centers and putting the focus on these urban centers. And these are the 125 largest U.S. cities. So just to sort of impress that this is an issue and it’s especially an urban issue in many regards, of these these 125 cities here they only account for 2.2 percent of the land mass in the continental United States, the lower 48 states.

[Slide: Pie charts of Top 125 cities account for 2.2% of land mass, and account for 38.1% of light reflectance; 5% of land accounts for 69.5% of reflectance; Almost half of the United States experiences light-polluted nights (Falchi et al. 2016)]

However they account for 38 almost over 38 percent of the light reflectance. So it’s sort of this disproportionate relationship between how much area they take up on the ground and how much light reflectance is coming from these cities. Sort of to just put this another way and hopefully convince you that you know it’s it’s sort of this this small area that’s causing a big source of the light, the top five percent sort of worst photo polluters across the U.S. are accounting for just under seventy percent of the light reflectance.

So we know it’s sort of a small area but the scope of artificial light and the contamination is quite large. So across the U.S. almost half of the U.S. has some photo pollution. So it’s you know a small area but nonetheless the scope of the photo pollution is quite large.

[Slide text: Can we quantify this exposure? Image: U.S. viewed from space at night, and a perched bird]

So can we look at this across the U.S. including all of these cities that are sort of encapsulated in this data set. So this is the U.S. and this is a composite of the light reflectance as measured by this mass of satellite. So can we relate this with a biological product, so if we could overlay this where the migrants are coming through we could begin to put our thumb on this is a region where we see a lot of birds coming through and there’s a lot of light to sort of prioritize where to make conservation efforts.

[Image: U.S. map outline]

So getting that biological product has been a challenge for many decades now and that sort of this revival of using radar to understand migratory movements. And we’re sort of just getting to this stage where we’re able to use sort of advanced machine learning, computational power, access to data sets, to actually answer that question.

[Image: U.S. map with NEXRAD system over it showing larger thunderstorms in the north]

So this is the U.S. NEXRAD system or these Doppler radars. Many of you are probably familiar with them. And on this image here what we’re seeing is precipitation or large thunderstorms sort of in the Upper Midwest here. And you know these are the same radars that are going to detect you know tornadoes coming through the Great Plains and hurricanes coming through the Gulf of Mexico. And as adept as they are at measuring when it’s going to rain or when it is raining, they’re equally impressive at measuring birds.

[Image: Same U.S. map with blue and green patched added, most heavily concentrated in the east and south]

And so all those blues and greens that just popped up are actually migratory birds. And those are classically filtered out by meteorologists. But our training allows us to dig into the raw data and look at you know all these birds.

[Image: Same U.S. map with the weather systems removed]

So we remove the weather, that’s our clutter now, and we maintain just the biology.

So just to sort of, I’m curious. I have a number of how many birds I estimate are in the airspace but just a show of hands, how many folks think it’s more than a hundred thousand birds? Okay let’s see how many’ll go down—over a million? over a hundred million? Okay. My estimate is 310 million birds in the airspace, so many of you are sort of along that ride.

[Slide text: 310 million birds]

That number is impressive in its own right. I’ve sort of thought of you know this this gimmicky trick to sort of hopefully imprint that this is a ton of birds. So if you are standing in one location, this is fairly gimmicky, but if 310 million birds flew over you and they flew over you at one bird per second continuously, it would take you 10 years to count to 310 million birds. So hopefully that sort of strikes you as a tremendous amount of birds. If not Adriaan’s talk will sort of get you excited as well. [laughter]

[Animation: U.S. map of migration activity, with lines moving across indicating migratory birds over time. The area with the highest migration activity is the central U.S. in both spring and fall, with increased numbers also in the southeastern U.S. in the fall]

So that’s one snapshot of what’s going on and we can look at this over multiple decades now and we can use millions of these samples not just sort of one 10 minute snapshot.

And that’s what we see here.This is a long term trend, the average movement of migratory birds across the U.S. airspace for the last 20 plus years. And what you see are essentially billions of birds funneling out of the tropics during the spring moving across in many ways the central flyway, moving up into Canada, the nursery for these birds where they’re ultimately will go to breed.

The same pattern is true in the fall, many migrants coming out of the boreal forest now. Or not. Let’s see if I can get this. Well nonetheless, envision birds funneling out of the boreal forest. [laughter] There it goes. But you can sort of see them they’ll come through, many still coming through the Upper Midwest, but that cloud of birds is shifted a bit eastward actually.

So this is sort of the long-term average of bird movements across the U.S. with the yellows being where most of the birds are coming through in spring and fall. So to sort of get back to my point here of we want to link these with light data.

[Image: U.S. maps of spring and fall migration data with arrows to U.S. map of light at night = Exposure Index]

So if we can multiply this light data by this biological product we can get an index for the spring and fall. And that index is sort of an exposure of how many birds are exposed to these lights on a given night.

So what I’m showing here are actually, I’ve done the exposure index and I’m just going to show you a series of cities ranked and how sort of quote-unquote how bad they are. You know how many birds are exposed to these these really potent lights on a given night.

[Image: City light maps by exposure index for spring and fall. Spring: 1. Chicago 2. Houston 3. Dallas 4. Los Angeles 5. St. Louis 6. Kansas City 7. Minneapolis 8. New York 9. Atlanta 10. San Antonio; Fall: 1. Chicago 2. Houston 3. Dallas 4. Atlanta 5. New York 6. St. Louis 7. Minneapolis 8. Kansas City 9. Washington 10. Philadelphia]

So Chicago, Houston, and Dallas are sort of the top three and they’re consistently the top three across spring and fall. But things begin to change a little bit as we sort of jump into the the remainder of the top ten. But probably no surprise that areas like New York City and Los Angeles, Atlanta are sort of coming into this this top ten of sort of quote unquote worst cities for for migratory birds. The fall as I said again is the same top three, so we’re really sort of putting our thumb on these are probably three cities we really want to focus in on doing lights-out campaigns when the birds are in the airspace.

And then the top ten sort of shuffles around a little bit as well. So we’re beginning to see some seasonal differences and I’ll just highlight a couple. So something like Los Angeles is in the top five here. But during the fall it’s not in the top ten and it actually drops all the way back to 35th in terms of that ranking system. So there’s some unique seasonal patterns of where the birds are moving through in their migratory routes. And then in the fall we start to see more eastern cities cropping up into the top ten.

[Slide text: Exposure difference Fall – Spring; Image: U.S. map showing exposure in fall in blue, mostly in the southeast, and spring in red, mostly on the west coast]

And sort of the reason for that is I’m just showing here is actually the reds are areas where we see more migrants proportionately, more migrants coming through and they’re they’re weighted by this underlying light mask here.

[Slide text: Threat higher during spring migration (west coast); Threat higher during fall migration (southeast)]

So during the spring on the west coast we’re seeing that birds are going to be exposed there, more birds are exposed to lights at night, so we have sort of a greater threat here along the west coast. And on the east coast we see the blues being where the migrants are sort of seeing a higher threat during the fall.

So there are some looped patterns going on in these migration systems here of migrants coming up the west coast and moving through a mountain flyway. And many migrants coming up to the central flyway and coming back towards sort of an eastern flyway.

[Photo: Black-and-white warbler with caterpillar in its beak]

So we know that many of these birds are impacted by lights in some way and we know how many birds are sort of in the airspace, but we also want to be able to put this into action and make conservation action. And it’s really tough to do that if you’re sort of reliant on the data coming in and making that decision.

So can we make a prediction of when the birds are actually in the airspace and make a forecast into the future, hopefully giving managers that make these decisions enough lead time to sort of prepare for something like a lights-out campaign or shutting down a wind turbine. And you know we know that you know one night there may be hundreds literally hundreds of millions of birds in the airspace and the next they seem seamlessly absent.  So can we come up with a good predictive model to sort of understand that?

[Image: U.S. maps of bird radar data, temperature, and wind with “Predict” arrow back to radar map]

So that’s exactly what we want to do is we’ve amassed all of this data, can we actually build it and pair it with known factors that drive migration something like precipitation, something like temperature, wind patterns all of these sort of known drivers of migration and can we link them back and make a prediction of when the birds will be in the airspace? There we go.

[Slide text: Radar training data (1995-2017) Build classifier New data, North American Mesoscale (NAM) forecast Migration forecast]

So this is sort of our pipeline for doing this and to put this into action, so we’ve already amassed as I said many decades of radar data. Millions of samples can be linked with meteorological data. If we can say that these are the conditions that stimulate migration, we should be able to learn these patterns consistently. My entire Powerpoint seems to be on a timer so I’m battling time here. So we can we can link these data with a classifier and we use machine learning techniques that allow us to do this in sort of new ways. It’s been fairly difficult to link very nonlinear, nonparametric results with complex atmospheric data, so we’re using you know algorithms that are you know in many ways drive things, like we suggest you watch this on Netflix or you know this song is recommended on Pandora. It’s sort of those same linkages of learning from past behaviors to learn future behaviors. so we can then link those data with meteorological forecasts. So meteorologists have been building forecasts for many decades now, and we’re leveraging that infrastructure to pair that with our models to make a migration forecast.

[Image: Migration forecast, April 23 2016, U.S. map of migration intensity. Highest intensity is in the central U.S. with 112 to 178 million birds predicted. Compared to U.S. map of radar from the same night, the central U.S. again has the highest concentration of birds migrating]

So we’ve done that and this is one such forecast actually. So this forecast is from a couple years ago now, it’s April 23rd 2016. And the way we designed our model was to say that our model has never seen any data from 2016, so it doesn’t know what to expect that year. It’s only relying relying on the meteorological data.

So in this map here what we’re showing is the reds, the yellows, the oranges are where we expect to see more birds, the cooler temperatures, fewer birds. We can overlay this with meteorological data like precipitation. So precipitation is you know from a birdwatchers standpoint where we expect to see reds plus precipitation those may be conditions where you see a fall out, many birds making landfall. But from a conservation standpoint that may be an area where you may see birds colliding with buildings or wind turbines that become disoriented, especially under light pollution. The same methodology allows us to estimate how many birds are in the airspace. So on this night we estimate between 112 and 178 million birds. And then this is actually sort of quote-unquote the truth. This is what was observed that night so hopefully you can see that you know we’re pairing these these intense movements with what’s actually going on.

[Graph: Predicted migration (cm squared km cubed) versus Observed migration (cm squared km cubed), 78% variance explained]

And you know I could show you image after image after image but for the sake of time I’ll just sort of represent it in a plot like this.

So this is showing our predictions along the bottom axis here versus what’s actually observed and hopefully this convinces you that we’re making really accurate forecasts that predict and account for this variation in where birds will be.

[Graph: Date (March to June) versus Total birds (millions) for several years with highest numbers in May]

So as I said we’re able to pinpoint where the birds will be, how many of them will be in the air space, and we can year-after-year detect how many birds will be in the  in the air space across the U.S.. In putting our effort or conservation effort on these couple of nights especially in late April into May when the migrants are coming through can be really powerful.

So you know on some nights we’re estimating as many as 500 million birds in the airspace, just a tremendous amount of volume. And those peak blasts of migrants only happen on a couple of nights. So if we can make accurate forecasts we can really do some conservation action there.

[Image: BirdCast website, “Bird migration forecasts in real-time,” with live migration map and migration forecast]

And if you’re interested in this we now have this going live on Birdcast.info. So this is the landing page for BirdCast. And you can see our forecast and then Adriaan’s live migration maps actually on the right page here. The forecasts actually sadly are shut down for the spring migration because we’re now at the tail end.

[Image: Migration forecast for night of June 4-5, 2018 showing highest intensity in upper midwest]

But this is sort of the the sneak peak of me having access to these data and producing them is that this is actually the forecast for tonight across the U.S. So we’re still making you know predictions and we’re seeing some trickle of migrants coming through the Upper Midwest on a given night.

[Photos: Several news articles about light pollution and birds]

So I’ll just sort of close on you know talking about this and motivating conservation action. Hopefully these forecasts and they’re already landing in the right hands of using these to try to mitigate birds colliding with wind turbines or colliding with buildings, beginning to understand how birds are interacting with lights at night. As I said Houston is one of the worst photo polluters and there’s just a tremendous volume of birds coming through that area. Houston Audubon has taken it upon themselves to get the information out to their community. To say this is when we expect birds that come through. If you can turn off your lights at night you know if your buildings above two stories.

[Image: eBird website, “Discover a new world of birding…”]

So trying to do action in that way. But also giving back to the core sort of audience of the Lab of Ornithology, the folks that love birds and bird watchers. Of trying to motivate them to wake up early and go out and compile an eBird checklist and hopefully those data come back to the Lab of Ornithology so we can continue to understand these migration systems. So with that I thank you for your time.

[Adriaan]  All right. How are you doing? Two rounds free. So I’m I’m Adriaan Dokter I’m also a postdoc here at the lab. I talked in a few slides about myself just to introduce myself.

[Image: Map of Europe and North America, with signs at University of Amsterdam, NIOO, and The Cornell Lab of Ornithology]

So I’m from this really tiny country the Netherlands which you might know from windmills, wooden shoes. But honestly yeah it’s like two years ago I came here to to the Lab of Ornithology but before that I actually had a whole career as a as a physicist.

[Slide text: Evolution into a movement ecologist; Photos: Adriaan working in the lab and field]

You see here me me behind my ultra for spectors—I almost forgot what it was called— the ultra-fast femtosecond laser which I’ve studied water molecules and it was only after my PhD actually that I became a bird researcher. Sort of me I’m combining my my sort of childhood passion for birds with with my actual work.

And I like this really maybe mathematical quantitative way in which physicists work. I’d like to apply that a little bit also in birds migration research and this whole radar work all these lots of data this kind of well-suited for that. So it’s my little niche. I also took a few years actually to become a real biologist working with brant geese, getting my hands dirty while collecting their poo and sitting on a cold dyke in the Netherlands.

[Animation: eBird map of North and South America with dots showing bird migration throughout the year]

So now I’m a bit of both, a physicist and an ornithologist I guess now and a movement ecologist. So let’s take take maybe a little step back from the radar and and just think about what this whole phenomena of migration actually is. and maybe you’ve seen this figure before the frankly sward my colleague made that and this figure a few years ago.

Like each of these dots represents one species of birds that is migrating across the U.S. and just if you think of it these huge populations of birds that is an enormous exchange of bird biomass that sort of moves around over over the planet. And of course these birds, a lot of is happening to them. It’s it’s the dangerous journey from north to south and they run into all kinds of adventures. And they might actually die along the way and then give birth to new birds when they breed. So there’s this whole cycle of life and death going on, and there’s not always the same number of birds around.

So that it’s changing all the time. Now funny enough like these processes especially of death when birds are dying, that’s something that we actually know not so much about. And it’s simply because it’s it’s already hard to track one bird as Cecilia explained and to understand how a whole population of birds is sort of changing and and dying and reproducing over this whole journey it’s actually quite hard to measure. Especially observations because of birds is, for example, you know in the spring it’s really easy to actually detect birds because they’re singing. In fall they’re very quiet so you don’t see them so actually to count them is actually also not so easy.

[Image: U.S. map showing birds on radar; Photo: radar]

So let me let me and our complication then is. Oh. So enter the radar-like the radar is actually really great tool if you’re interested in counting numbers of birds and seeing how these things are changing because it’s simply a machine that is sort of always doing the same thing and it’s just counting always in the same way. So it’s really good at at sort of counting birds.

[Slide text: Long time span (25 year archive), Large extent (143 stations), Abundances (aerial biomass)]

On top of that we it also has a very long time span, 25 years very large extent. So we can sort of zoom out and and and really count maybe the numbers of birds that are in the whole of a fan of the net of the of the us. Now this is the raw data. Scout showed you earlier we now have sort of all these tools to dig into these archives of 25 years of data and to research with it and you might think 25 years that’s actually a long time why why haven’t you guys been working on this already 15 years ago it’s a little late.

[Slide text: Data, 100s of hard disks, radar archive: ~2 peta bytes; Extracting bird info, 3000 computer hours/year, Big Data NEXRAD on AWS, amazon web services, BirdCast]

Well actually there’s a reason for that and that’s simply because these data they were not always there. Or well the data but we couldn’t really work with it.

And and maybe what’s in the back of it all is also why we have now so much internet and computers and these companies like Amazon and Google, and they they they sort of changed this whole game in which we can can do science. They have the huge data farms, thousands of computers and it’s really easy to store the data. And that’s why also we are lifting a little bit on that. So it’s sort of a big data research fields where sort of the data that we deal with there are owners of an artist’s large the archive to extract that bird information takes thousands of hours if you do that on your single computer.

But now we have all these big internet company companies and in which we can use their sort of facilities and then sort of what I would use to take a month then I can do that now in an hour because I just put two hundred computers to work. So that’s that’s the reason that all these things are so much easier.

[Animation: Bird movement across the U.S. on 08 May 2017, www.birdcast.info, Adriaan M. Dokter, 2018]

Also that we have now BirdCast and Kyle alluded to already to like you can sort of watch now to these radar movies in real time.

If you go to the website of Birdcast, and yeah I mean there’s so many computer power that we can see you can serve you these data just just as we go. So this is for a single night in May 2017. Just really big migration night also. And now and basically we can do it now for every every night.

[Animation: Bird movement across the U.S. from August to October 2016]

So he another movie now we’re gonna sort of see sort of the progression of migration nights over full season here in August 2016 and you see sort of all of a sudden comes to life. We all would never really see that that you see this so you sort of see starting these waves of bird migration moving over the continents. And basically quantifying how many birds are now there was a really big migration wave, there’s only few of them every every season.

[Animation: Total passage in spring 2016, accumulation of birds throughout migration; 3,550,000,000 flying into the U.S. and 2,560,000,000 leaving the U.S. for Canada]

So what I did now sort of to sort of started to use these reconstructions of migration to try to do some science with it and first one of the first thing I did is like sort of counting all these nights together. So let’s do that. So and just take all these all these individual nights that we just showed to have start to add up for each location how many birds are flying over and then you get sort of these accumulated maps of migration. And that sort of looked like this. So you see many birds through the central flyway, a lot of migration there. Many much less birds in the in the West. And I sort of wanted to know okay how many birds are there now flying in and out of the U.S.

So what I sort of did, this make sort of these fences along the borders of the U.S. [laughter] and well I’m not gonna call it a wall now. But these fences here and and it’s nice because of course it doesn’t really matter how the birds are flying over that fence I just I just we have such a large overview that I always captured them no matter what. So that that’s really good for counting so it doesn’t really matter if they one year they go a little more to the left or a year more to the right. And then I simply count how many birds there are so and then I come to this number in the spring. 3.5 billion birds coming in. So can do the same now across the northern border how many birds are now leaving again to Canada. So a new data and then I find 2.5 billion birds. So huge numbers it’s kind of unbelievable.

[Animation: Total passage in autumn 2016, accumulation of birds throughout migration; 3,970,000,000 flying into the U.S from Canada and 4,720,000,000 leaving the U.S.]

Let’s do now the same in autumn. So again I’m sort of gonna enter everything together just try to remember how many birds we had. And forgot myself now ready 3.5 billion and 2.5 I think. So what do you think? Are you gonna have more or less birds in the fall? More yeah of course more because that’s of course there’s they’re there so there’s new birth happening in there going to Canada to reproduce. So we expect to have more birds. So let’s see. Indeed we have now 3.9 billion words coming back north and 4.7 billion in the south. So let’s remember that. So that you can see a hint a little bit we’re not only looking at movements we’re also trying to see a little bit this cycle of life and death. Yeah you’re seeing mortality on one hand we also any seeing maybe new birth and a combination of these two things.

[Image: Difference Spring/Autumn; map showing more birds in autumn in the central and southeastern U.S. and more in spring on the west coast and southern Texas]

And you see that if you take the difference between these accumulated surfaces between spring and fall. So I took these surfaces of how many birds flew over each space in the U.S. and I took the differences between the fall and the spring. And you see if there’s more birds in the fall it’s red, if there’s more birds in the spring it’s blue.

So you see this map shows up a little whitish but in fact it’s actually mostly it’s mostly red which means almost everywhere you see more birds in the fall and that’s indeed this new birth of birds. You also see there’s mostly red in the left and that’s what Kyle already mentioned we have we sort of have these looped migrations. So in the fall they’re going a little bit more towards the east probably because the winds are mostly blowing towards from west to east so they get blown a little to the west.

And also in the fall and for the way in the west of the country birds are coming down mostly through the mountains and then coming up through the Central Valley in a in the fall. So you sort of see both these shifts in spring and fall and that’s again that’s why I take these sort of coast to coast transects to count the birds because they they move in a different way in a spring in a fall. But because we have such a large overview the radar networks we can still get sort of a reliable count in spring and fall as we can compare.

[Image: NEXRAD Radar: measuring mortality; bar chart showing more birds in autumn for both northern and southern transects]

So that this is sort of the same data but now sort of in a bar chart. So clearly in the spring we had less birds in the fall both for the northern transect and for the southern transect. And now basically I can sort of distract from that now sort of indices or sort of metrics that tell you something about life and death. For example, I can just simply look how many birds are going south in the fall and how many coming back, and the difference between the two is just what we have lost and that is what has died.

So one thing that I find is that if you do that you see that basically in the north that northern transect there’s there’s less birds coming back, so there’s more death from the birds. And if I look at the southern transect and see what comes over there in the fall and what comes back in the spring, it’s actually quite a few more birds that are coming back. So let’s think of it about why why why would the difference be there. And this is sort of a schematic that in which I try to summarize it all.

[Image: Biomass cycles of birds in arctic, temperate, and subtropical habitats showing reproduction, fledging, migration, and wintering showing more biomass in while reproducing]

Sort of these sort of biomass cycles of birds moving across these northern and  southern transect. So you you sort of see if it swells in the breeding grounds and in this sort of bar gets a little wider because more birds in an over the season they start to move down across the transect and they start to sort of die you get less and less birds.

[woman] Isn’t there a difference in life expectancy of some birds?

[Adriaan] Yeah definitely, and maybe that’s what I’m getting through that maybe these are different strategies of birds.

[Slide text: North transect -wintering at temperate latitudes

-shorter distance migrants

South transect -wintering at tropical latitudes

-longer distance migrants]

And and and if you look at now that at a northern transect there’s if you if you look sort of based on what we know of the distributions of birds and what we expect which species have to move over there, is mostly sort of these north wintering birds, that winter in temperate latitudes, there’s just a lot of these birds like robins and sort of all the kinds of sparrows. They don’t really go to South America, many of them to stay in the U.S. to winter. They’re sort of more short distance migrants.

Well if you would go more to the southern transect to southern border of the U.S. there is a really high proportion of birds that actually all go to South America, it’s more these neotropical migrants. Of course there’s also neotropical migrants in Canada but on average we have many more neotropical migrants if you would look at that southern transect than we if we would look at at the northern transects.

So also that the migratory distances that the birds have to go are different. Typically these birds in the south they have to migrate very far and once they have crossed the transect the birds in the north a little less far. And one of the things that we we believe or as we always thought that migration is actually a challenging thing, there’s also the kinds of dangers that are happening on the way so always our expectation was a lot of birds when they die we think the birds that have to migrate a lot, probably they die a lot.

So if you would think about that if the birds that have to migrate a lot might have to migrate farther are mostly the birds in the southern transects you would think maybe maybe those are the ones that don’t come back in a really high proportion. But actually that’s the opposite of what we find.

[Slide text: Survival- population loss in winter 0.64 +/- 0.07 (north); 0.74 +/- 0.02 (south)]

So if we look now at survival of how many birds are dying we see that the survival rate for birds in the north is about 0.6 and in the south is about 0.7. So actually in the south it’s most of the birds coming back. And so what if I started thinking about it that’s kind of strange maybe because these birds have to migrate very far but of course there’s many more different things that are different. These birds are migrating to the tropics while the other birds are staying here in the winter where it’s very cold. so what I think is what probably is going on is that maybe we’re seeing here a reason also why birds maybe migrate in the end. They migrate probably just to go to a place where it’s nice and warm, there’s lots of food, where they can survive very well.

So therefore you think actually these these birds that these long-distance migrants that’s going to the tropics they have a good time they come back and they survive. While the birds that have to stay here in the cold winter, those might actually be the ones that have a lot of death and mortality in the winter. Of course evolution has thought about this and there are different reasons and sort of the strategies the life history strategies as we call that these birds are different so you can either have sort of a northern bird that sort of winters in the U.S. you have to have a strategy of a lot of you have to make a lot of offspring so that you can live with this little bit of death that happened that a little bit more death. While you got the other strategy might be your long-distance migrants then you have this benefit of high survival in the tropics and you might have to have a little less reproduction and you can suffer a little more that more death during migration. There’s all these trade-offs and and different balances.

[Slide text: Recruitment- population growth in summer 1.60 +/- 0.07 (north); 1.36 +/- 0.02 (south)]

So you can also do the other way, we can also look at it the other way around like how many birds are being recruited. So that’s what we can also estimate with the radar data and then you see that for every bird that comes north in the north, the northern transect for each bird that goes north so you get about 0.6 birds are coming back. So a lot of them die already because yeah fledglings you typically have maybe three or four chicks we never see them back, they they all died already earlier and we see only 0.6 coming back.

In the south we see only for each bird coming back we see 0.3, 0.4 coming back so probably because maybe some birds died already on migration and also because again there’s this different balance in between, yeah you have to balance your death against, yeah how much death you have if you have a lot of death you need to have to produce a lot of chicks in the end it has to balance out.

[Slide text: Raw data Bird movements Seasonal bird counts; Movement and Population dynamics overlap for 25 years]

So that’s sort of my story, that’s kind of what I wanted to show you. How we go from this raw radar data that has been sitting there in these archives for 25 years, access to them now, that we can go to these bird movements and reconstructions of that. And from that we actually can make sort of these seasonal counts of birds from which we can take another step as to actually get sort of indices of reproduction and reproductive success and indices of survival and mortality.

So you see that in the field of movement ecology that we have always had and population dynamics that were typically always very different kinds of different researchers and people who were doing it and we sort of now with the radar research we can sort of try to bridge the two sort of and sort of look at population dynamics or and life and death of a whole avifauna now because of course we’re looking at all the birds at the same time for twenty five years.

So that’s maybe where I’m now with my research I want now want to go into digging into the archives and see okay are there now certain sort of certain years when there’s many more birds than others order certain years when there is much more death and why does that happen? Can I find something why it happens?

And basically maybe one of the most basic questions you might have heard that long-distance migrants that a lot of the long distance migratory birds are in decline and are not doing so well. To be honest as migration researchers we still don’t really know why that is. Is that now because there’s problems in the tropics where so much is changing or is it here in the north where it’s also changing a lot to our environment? Or is it both at the same time? Maybe to look at this annual variation maybe we can maybe figure out which sort of dramatic years when there’s a lot of death and maybe get a finger behind yeah but deeper understanding of these processes of life and death.

I said already in the end birth and death has to be balanced for a population to be stable, if it’s not then it will either increase or decrease, so I’ve been looking a little bit already in the long term data set to see as the number of birds in the U.S. changed now in the last 11 years I couldn’t go back 25 years yet. And then this is sort of what we what I find.

[Slide text: Declines in bird biomass detected by radar, preliminary analyses: 1-3% annual decline 2007-2017, most declines in Eastern U.S., >10% loss in last 10 years; Image: Map of U.S. showing %change/yr of bird biomass with largest declines in the northeast and fewer in the west]

It’s sort of a highly mobile output there’s a lot of data massaging going on here but this is final results. It’s sort of a map that looks mostly red and red means decline so it seems to be that over the last 11 years we’ve sort of seen and decline in the numbers of birds of around 1, 2 percent a year. Don’t pin me down on the numbers yet, the data is still very new, but that is sort of worrying in a way because of course radar is also a tool that looks at all the birds and mostly therefore common birds because those are showing up the most there’s simply more common birds by definition so it means that sort of across the board across the whole avifauna at there seems that we are seeing this decline and sort of suggests that something sort of fundamental might be might be wrong if we see that across so many species showing up.

So I was working with Kyle, I’m also collaborating with with Kyle, I’m also collaborating with Kyle but I want to elude to Ken who is sitting in the back of the room, who is doing a lot of work also on population changes and not with radar but simply with the with the good old very important count data of breeding birds like the breeding bird surveys you might have heard of.

[Slide text: Net population change

-Do we see a net change in bird populations over time in breeding bird surveys as well?

-How many birds have we lost?]

And of course I was looking at these things in in the data and Ken was looking at the trends and we thought okay are we seeing now the same thing?

[Slide text: Breeding bird surveys- birds lost 1970-2015, very preliminary unpublished data!

-Net population loss of 2.3 billion native landbirds since 1970

-Net loss in ALL habitats, including habitat generalists

-Largest loss in grasslands (700 million birds; 56%) and boreal forest (500 million birds; 35%)]

Have we lost birds? So together with the Partners in Flight again we looked at this changes in breeding population surveys and here we express of how many birds we have lost since 1970. So we have taken about the breeding bird surveys over this much longer time period than I looked at like, now 35 years, 45 years and see if we take 1970s as the standard, as the baseline, has there been an overall loss in the number of birds? And we first thought no probably not because some birds have increased probably. But actually we were quite surprised to see that actually there is a net loss in the number of birds from these data. And they’re very preliminary, unpublished data so also again don’t pin us down yet, we just giving you a sneak preview here of unpublished results.

What seems to be a net population loss of 2.3 billion native land birds in 1970 is sort of the number that is in the same ballpark as my radar estimates in all habitats and most loss seems to be in grasslands, boreal forests. So it seems to be a sort of general general pattern and I would like to say it’s important actually to think about keeping our common birds common because of course species go extinct, species first decline before they go extinct.

[Slide text: Keeping common birds common

-Species decline before they become endangered or go extinct

-Phenomenon of bird declines globally, loosing spectacle of mass migration?

-Loss of ecosystem integrity and services]

And if you’re seeing that across the board it means that we, yeah, that something fundamental is changing in the environment and we have to figure out where, where it may be directly, yeah where this problem is happening and whether we can do something about it.

[woman] Can I ask? When you’re doing radar, you can’t tell, you can’t see the birds?

[Adriaan] No, you can’t see the birds.

[woman] So you have to look at them during the day to see the birds to see which birds are flying?

[Adriaan] That’s also true, yeah.

[woman] So you count the birds and you know there’s birds flying, then you have to look at them during the day to see which birds are flying when.

[Adriaan] So someone in the public saying like we should actually look, you should also, you shouldn’t look only at night with your radar. You should actually look also during the day, what’s actually on the grounds and then you know which species there is. I think that’s a really good remark and maybe that’s something something that we also are thinking of like and of course there’s also a revolution going on in this is also data-driven in a way with birds observations. You might have heard of the eBird data that people are collecting. That’s also a huge exponentially growing growing datasets that is species specific. So there seems to be a sort of natural connection between using eBird to see what’s on the ground and what species are there and then look with the radar actually how many birds there are exactly and what’s happening at night they sort of complement each other in a natural way.

[woman] You can’t do one without the other, it seems.

[Adriaan] Yeah and you see actually, I put here this figure of this dove which you might recognize as the passenger pigeon, maybe as a sort of reminder to us all that of course the passenger pigeon was also super common. It’s about three billion birds there were, and they were hunted to extinction in a matter of 30 to 40 years. That’s about the same a number of birds at the end that we estimated that we have lost maybe over this time period since the 1970s. And then these people didn’t have these, they might have looked better but they didn’t have all these great tools that we have now and with the radar data and so maybe let me put the final slide up which is actually more positive story.

[Slide text: Thank you!]

I just love to look at this data and and I hope many people do that and I think all the tools that we are as a group are making for the for a from the radar side of things and we also do that with eBird at the lab is to sort of yeah bring to the to everybody also that you can see this phenomenon of the migration that people are aware of that is happening and that you can see the data, get people engaged and hopefully get people enthusiastic about phenomena of migration and measure the declines actually and once measuring is knowing, and then we can hopefully also do something once we once we dig up the good data.

So I think that that I’m gonna leave you and can maybe open up for for questions if they are are there. Thank you all for your attention.

So now you have to also come here. [laughter] Are there other questions or is it? Yes?

[woman] How do you account for the gaps in radar in the western United States?

[Adriaan] Yes that’s a very good question. So actually that’s what I’m actually, the reason that I’d, so the question is how do you account for the gaps in the radar data and because of course there’s the mountains in the Rocky Mountains in the west and it’s true that part of the fact that you don’t see birds there is also, because the radar is standing on top of a mountain and then the birds are flying under the radar. That’s part, the solution that’s for my case is the transects I chose them in these two areas there are actually not so many mountains, so there that’s actually a reason that I only have the northern and southern transects and I didn’t draw drew more of them. So that’s one way to account for it but yeah we cannot fully account for that. But it’s good to be aware if you look at these maps that some of the radars in the west are a little insensitive to the birds because they’re flying under the radar. Yeah, yes.

[man] Kyle, you mentioned when you did the top 25 cities you call it reflected light.

[Kyle] Yep.

[man] Reflected from where?

[Kyle] Yeah so it’s coming, the question was.

[Adriaan] Maybe come here otherwise the people cannot orient.

[Kyle] The the question was for the this this light reflectance data set, where is the light coming from? So the light is literally the light on the ground that’s observed from space.

[man] So it’s not reflected, it emitted.

[Kyle] And yeah. It seems synonymous of yeah, I can change the verbiage if if if that sort of that fits better but NASA calls it light reflectance so they’re much smarter than I am and have have many more engineers than than we do here so I go with their terminology, but yeah it is emitted from the buildings and observed by space, but yeah.

[man] We have a question from our online chat. Are birds attracted to light in general, or specific frequencies of light? Can we use different colored light, or softer light, would there be a difference?

[Kyle] Yeah I think you might know more about the wavelengths, so…

[Cecilia] Okay so the question was if different wavelengths of light affects migratory birds differently I think, and I think the short answer is yes but we’re not really sure how. So there are some experimental studies that show that they are attracted to some wavelengths more than others but it’s still very unclear also how detrimental certain wavelengths are, but yes there’s probably as a difference so there could be things to be done there.

[Kyle] Just to sort of follow up on that too, so a good example of that is sort of the work that is done with communication towers, so the lights at night that that pulse on a communication tower or red lights, so they’re sort of you know, if it’s a constant white light that’s really the worst for a migratory bird and many migratory organisms and things like bats as well, but a pulsing red light is sort of the best combination that reduces the attraction to these communication towers. So there is some research going on that has pushed that in that direction as well.

[woman] Do some of the birds have some sort of radar so they know where they’re going in the night? It’s dark, do they have radar so they don’t bump into anything?

[Cecilia] Okay so the question was if the birds themselves have radar so that they know where they’re going and if they, so they don’t bump into things. Well they don’t have radars, they do have different senses that tell them where they’re going. So they have different magnetic or they have different compasses, yeah. So we know that they use both the stars as a method of the orienting but they also have a magnetic compass where they can detect the magnetic field, well mostly the magnetic field for long distance orientation. And they can also use the position of the sun at sunset and polarized light and things like that, but on them well they don’t, yeah they fly much higher than that during night and I think mainly for that sort of not bumping into things it’s visual cues that they use, so they would need some light for that.

[man] And for not bumping into each other they also use little call notes.

[Cecilia] Yeah that’s true, they also use call notes for not bumping into other birds. I think that was first.

[man] Do you find more birds die on overcast nights?

[Cecilia] Yes more birds are killed in collisions with buildings and stuff like that on overcast nights and on nights when there’s fog and visually-impaired situations, yeah.

Yeah yeah absolutely I don’t think so I don’t think it’s that’s common for diurnal migrants to collide with buildings, not that I know I know. Oh that we don’t know we haven’t looked into that, I don’t know but presumably.

[Adriaan] Yeah and it depends on the species, so for example for certain nights and with certain hawk species that funnel through wind farms for example, there’s actually also evidence of a lot that can can happen that there’s quite a few bit of mortality during a day as well so, yeah it really depends.

[woman] Are you able to differentiate between bats and birds? Can you tell?

[Adriaan] The question is whether we can differentiate between bats and birds. Well actually we have a campaign now running with us and dedicated bat radar in Texas to, next to a weather radar to figure that out. It’s not gonna be easy, but maybe yeah especially with a small-scale radar that Cecilia showed, maybe, what do you think? Maybe, maybe.

I am, yeah that, so maybe a small proportion, yeah but if you, just the population size of birds are so much more humungous than of bats that probably it will be small backgrounds but yeah we don’t we don’t exclude them actively, no.

[woman] It seems like a big limitation of radar is you can’t detect different species, so I was wondering if there’s any other technology on the horizon that would enable you to do this kind of tracking that’s more species-specific [cough] as opposed to looking during the day time to see what you’re seeing on the ground versus night.

[Kyle] Yeah so the the question was talking about one of the the biggest limitations for these radar data are not knowing the species and sort of what technologies might be on the horizon to sort of fill that gap. There’s been a lot of work, so data combination and data integration is sort of one obvious thing that you mentioned as well of. We don’t know explicitly what the species are on the move in the airspace but we often know what’s on the ground, so we try to make those linkages to fill that gap. And as one of the gentlemen here also mentioned that acoustics is another way of explicitly knowing what’s in the airspace so many of these birds, especially the songbirds, the things like the sparrows and warblers and thrushes will give unique species-specific flight calls. So we get an indication of what’s up in the airspace.

We may be able to discern, you know the assemblage of warblers or that it’s dominated by thrushes on a given night. But it’s not complete and it’s still difficult to extract these data. Audio data are sometimes laborious and how how much time it takes to pull out those flight calls. And there’s also been a lot of work on just explicitly tracking individual birds, of putting things like GPS tags on individual birds and seeing where they they sort of navigate to their wintering and breeding grounds and tracking them all year round. So those are some of the big technologies. There’s also, you know, a campaign an icarus campaign that you know has launched a a satellite that has a sort of receiver that can track these birds from space now. So those are sort of the spectrums of work. We’re working on understanding the system of migratory birds on sort of the grand, you know, the largest scales we can, and then there’s also this other end of the spectrum where you could just track individual birds of known species, of of known age, of known sex. So that’s sort of the most detailed work, but you you suffer from going from four billion birds down to you know tens if not hundreds of birds so that’s sort of where we’re operating in.


[Adriaan] So the question is there’s also airplanes in the sky, in the sky and and they’re flying through these waves of migration, so isn’t it dangerous for the birds and for the airplanes at the same time. Yeah I think so. Well the advantage of with the airplanes is that at some point in flight, 10 kilometers at the cruising altitude is typically 10 kilometers and there’s very few birds there, so it’s mainly a problem with takeoff and landing, and then also mostly the larger birds. But I think that the this is a good example of maybe the applied use, also of these radar networks that we start to see these migrations now we start to predict them, and definitely airports are some of the parties that are interested in this in this type of data. And they’re also dedicated bird radars being developed specifically for airports that is surveyed the runways and their dream is also maybe in the future that they can say, ‘oh there’s a flock of Canada geese going on the runway, hold the plane for three seconds’ because they want, they don’t want any major interruptions of their flight business because it’s way too expensive. They’re way too many stakes. So but maybe sometimes holding off for two seconds is the difference between collision or not.

So typically the migration is happening up to like most of it is below a kilometer actually but we see them up to three, four kilometers. Very high, and sometimes you have very good winds, for example at three kilometers and it’s still amazing to us, on what someone else was saying, how are these birds doing this in the middle of the night? That so it still surprises me that there’s this good layer of air, good supports winds, it’s three kilometers high, it’s pitch dark, and then they know how to find it. And they have to reference their own speeds with respect to the ground and it’s pitch dark so I don’t really understand how they do it actually. So that’s nice that are still these mysteries.

[Anne] I think we could maybe take one more question. Is there one more question?

[man] You mentioned windmills. That made me think of infrasound. Has anybody been working with this data, both natural and anthropogenic sources of infrasound?

[Kyle] Yes the question was sort of in the the context of emitted sound in reference to wind turbines in infrasound. So the sort of the range of that the most birds sort of hear in is is above infrasound and sort of these low emitted wavelengths essentially are most susceptible to things like bats actually and it’s sort of at the other end of the spectrum of in that their their eardrums sort of rupture from this this low sort of energy sound. And that you know Barrow trauma is known as it’s known in that sort of rupturing of their eardrum causes disorientation and many of them collide with the wind turbines or outright you know will die as a result of it. In regard to birds we don’t know probably much and it seems unlikely that they would be impacted by that sort of low-frequency sound. High frequency sound is maybe a different you know perspective as well but my feeling is that it was probably negligible for migratory birds. Thank you.


[Anne] Thank you all for coming.

End of transcript

Join three of the Cornell Lab of Ornithology’s Edward W. Rose Postdoctoral Fellows, for an evening that will open your eyes to the unseen and mysterious activities and patterns during migration. Cecilia Nilsson explains why we use radar to study migration, and uses her research as an example of how radar can be used to study how birds migrate and how their migration is shaped by winds. Kyle Horton discusses his use of radar to quantify and forecast migratory flights, from small to large scales, highlighting the impact of anthropogenic light at night on nocturnally migrating birds. Finally, Adriaan Dokter talks about how he uses the radar network to count the number of migratory birds leaving and entering the United States. The team explores where birds migrate, when and where they die, how successfully they reproduce, and how North America’s avifauna has changed over the last two decades.