[Chris Saker, York University] So it’s four thirty in the morning and we’re making our way to the roost cavity being used by male pale-billed woodpecker. We’re hoping to get there before first light so we don’t disturb the birds and we get a really good chance to observe them at the roost. Right now the concern of course is not getting bit by, bit by snakes so we’re just keeping our eyes open. I mean we’re okay they’ll get out of our way. They feel you, the snakes feel you move, right. [In the rainforest of Costa Rice two ornithologists test a device designed to imitate the sound of a wild bird. If it works, it will lure the bird in and allow them to observe its behavior… up close] [Pale-billed woodpecker, Campephilus guatemalensis] There it is. So this is, so this is the tree. — [Martjan] Oh, this is the tree you’re going for. Excellent — [Chris] The one with the cavity in it. — [Martjan Lammertink, Cornell Lab of Ornithology] [Martjan] We’ve seen woodpecker chips from from the cavity above. Some of them are kind of wet and soaked and they’re starting to lose the color and they’re falling apart, so those are like, you know, three weeks old maybe, a month, but then there’s these other ones and they’re really crisp and fresh, meaning that it has been working on the cavity off and on over the past few weeks, and it is still a very active roosting cavity. Woodpeckers with this special anatomy they have for banging on trees, they use that anatomy not just for for searching for food and for making holes, but they also use it for communication. As most other woodpeckers use long rolling drums, pale-billed woodpeckers use this very short bom bom, two-note drum, it’s very characteristic for that group. The problem for us is how do we design a calling device that accurately imitates this knocking sound so that we can draw the birds closer to us to study their behavior. — [Chris] When I found out I was going to be doing my research here in Costa Rica with pale-billed woodpeckers, I contacted Martjan and Martjan said “Yeah, yeah. I’d love to collaborate on something with pale-bills. This is a good opportunity. I’m going to send you a prototype of this is double knock box we’ve been working on,” and when he said that I thought to myself wow this is great, I’m testing vocalization playbacks and I’m doing double knock playbacks, this fits into my study perfectly. What a great opportunity. — [Martjan] The double knock of all these Campephilus woodpeckers is a very simple but also quite precise signal that you need to imitate. — [Chris] I remember the day the double knock box shows up on my front porch, and I just cracked up when I opened this thing, it was the goofiest-looking invention. — [Martjan] The double knocker is incredibly simple looking to the casual observer. — [Chris] I remember bringing it into my supervisor and walking into his office with this contraption. The look on his face, his jaw dropped and I could just, I could just see the thoughts running through his head: is this kid serious? — [Martjan] It’s standard protocol to do a series of seven during one minute, and then have a four minute pause, and do a second series of seven. We’re broadcasting these sounds through the forest, but we’re not exactly sure how the woodpeckers will respond, or how effective the tool will be for bringing the birds to us. — [Chris] Looks like a great location, and it is, but no luck so far so we’re going to move on. You win some, you lose some. — [Martjan] From the beginning we considered doing a handheld imitation of the double knock signal, using two sticks or two stones, but it’s very difficult to consistently get the signal just right with the right spacing and the right ratio between the two bangs, and so we started looking for a mechanical tool to give a consistent imitation of that signal. — [Chris] There are recordings of Campephilus drumming, of double knocks, and the recordings can be used through an amplifier to call in Campephilus birds. The problem is the amplifier doesn’t carry the sound through the forest. The sound doesn’t sound real and it stops short. — [Martjan] The spacing between knocks needs to fall in, in a fairly narrow range of between 70 and 110 milliseconds, and the second knock needs to be less loud than the first. So we needed a tool that would consistently imitate that signal. One of the things we are concerned about is that the signal might actually be too loud and spook birds. — [Chris] It’s a weird time of day, and we’ve got some wind, so… it’s tough to know what you’ll get. One of the coolest things about what we’re doing here and about the double knock experiments in Costa Rica is we’re working on actionable science, it’s, it’s conservation science that works here in Costa Rica that helps develop a better understanding of pale-billed woodpecker behavior, territory size, hopefully that will be applied for conservation in the tropics. I think that’s probably one of my favorite parts about doing these double knock trials, I know it’s, it’s for a good purpose in the end. We can hear double knocks at any time, we have to keep our ears wide open. We know they’re here, let’s hope they’re hanging out in the vicinity. It’s not always the double knock you here first, sometimes you just hear them fly. Occasionally they’ll come in close and they won’t double knock at all. — [Martjan] There you go, that’s it for sure. — [Chris] We can hear some light tapping from the bird, which usually means it’s looking for good resonance. Seeing a pale-billed woodpecker is something I never take for granted. It’s just a phenomenal, phenomenal bird to look at. For a pale billed woodpecker, that bill, that powerful, ice cream cone of a bill, that’s their first survival tool. It really is the means to their survival in this forest, and everything from their feeding, to where they sleep at night, to where they raise their young depends on that powerful bill. — [Martjan] Wow, that was cool. — [Chris] That was wild, for sure. Good session. — [Martjan] Having a conversation with a pale-bill, that’s so cool. — [Chris] I’s not often you get to talk territory with a bird [laughs]. — [Martjan] The test went very well, we were really pleased with the results. First of all the birds respond to it in a consistent way, and also very encouraging result is that they are not too spooked by it. They don’t leave their home range, they just come back to their roosts at night, so that’s exactly the result we were hoping for. — [Chris] I think one of the things I’ve come to appreciate most about the double knock box is its simplicity, and it’s a reminder that science doesn’t always have to involve rockets. Science can be simple it’s, it’s problem solving, and this is, this is great problem solving. — [Martjan] By the way, there is a pale-billed woodpecker foraging here, about 10 yards, there that flash, it’s now on the big tree, so this is going to be awesome, man, let’s do some double knocks.

End of transcript

Ornithologists have discovered a way to mimic the sound of a Pale-billed Woodpecker using a “double-knock box.” Originally, ornithologists tried amplifying a recording of the Pale-billed Woodpecker’s double knock, but the sound did not carry through the forest in the same way that it would in nature. Although it appears to be a very simple contraption built from wood scraps, the double-knock box is a precision instrument. It consistently mimics the signal with the right amount of spacing between each knock, and the second knock is always less loud than the first. The knock box is loud enough to lure in Pale-billed Woodpeckers, but not so loud that it scares them away. Learning how to communicate with pale-bills is one of the first steps in understanding their behavior.