There are certain places during migration in winter where you just can’t believe the amount of bird activity and the diversity of species. Places that are magnets to migratory birds. Louisiana’s barrier islands are one of them.
Between Louisiana’s marshes in the open, bountiful waters in the Gulf of Mexico lies this ephemeral ribbon of delicate sandy islands. They provide the only sandy habitat the region and enable great concentrations of birds to utilize the food-rich waters of the Mississippi Delta. During migration and in winter, birds converge there from all over the continent.
This Sanderling comes from the High Arctic. From the Western prairies the Long-billed curlew. Least Sandpiper breed across Canada’s boreal forest. and Western Sandpiper come from coastal Western Alaska. As many as 30 shorebird species make use of the islands during the year where they join the pelicans, terns, skimmers, and other birds to reside there year-round.
At first glance the habitat appears to be rather uniform, but the multitude of shapes, sizes, bill types, behaviors reveals a much more complex picture. Different species forage in favorite micro-habitats and they use the unique tools they possess to harvest particular sizes of prey and types of prey.
One bird that really stands out is our largest shorebird — the Long-billed curlew. They have this incredibly long decurved bill and they’re able to reach things deeper in the sand than any other species. You’ll see them walking along and sometimes they’ll run forward because they’ve spotted a crab or something that’s darted down into its burrow and they’ll take this long bill, shove it down into this hole and start feeling around with the sensitive tip of the bill to find the prey item.
They’re adapted to reaching these burrow dwelling animals that tend to live farther down in the sand like certain species of crabs and shrimp and they find most of them by foraging in the higher tidal areas where the substrate is drier and firmer.
Marbled godwits are these tall graceful shorebirds. They can live to be thirty years old. They’re usually in these small flocks foraging in shallow water and they’re usually following a receding tide. And what they’re doing is using this long slightly up-curved bill and they’re more of a tactile forager.
They put their very sensitive bill into the sand repeatedly in areas where they have a high probability of locating the food items that they’re after which includes small by bi-valves like clams and types of marine worms.
The Ruddy turnstone is a really interesting bird to watch. They’re very opportunistic in the way that they feed and have a lot of foraging methods. Their body and all of its components are really put together in a way that gives them a lot of leverage and strength for pushing things around, for walking, for clambering over things on the beach.
They’ve got this stocky, stout little body and these short, very powerful legs and feet. They’ve got a short strong bill and they use these attributes basically to muscle things around. They’re out there flipping over shells, pulling through seaweed, pushing with their body, and digging things up, and finding little crustaceans and other small invertebrates to feed on.
Western sandpipers do a lot of their foraging like a lot of the other very small sandpipers– by probing and pecking near the wet surface for a very small size class of organisms. It’s incredible to watch them because they’re foraging and you don’t really actually see them catching anything. They’re repeatedly pecking or probing or sifting through wet sand and you know they’re eating things, but their speed and reflexes are so much faster than ours that we can’t even make out what they’re eating. They’re just on this constant fast-paced quest for food.
The Piping plovers and Semi-palmated plovers do what is a sort of run-stop-run foraging method. They’ll run for a little while, stop, survey the area around them, spot something and then run and grab it. They’re primarily forging by sight. They have large eyes, they have great sight, and they just have this little short bill so they’re not probing deep into the substrate. They’re locating things on the surface by sight and running over and grabbing them over and over and over.
They’ll also use the technique where they’ll put one foot out in front of them and sort of wiggle it on the surface and this might disturb potential prey so they move and they can spot them better.
Reddish egrets foraging technique is spectacular to watch. They’re basically herding and flushing schools a small fish in the shallows and they do this by running and leaping and raising their wings. They’re basically corralling the fish and trying to corner them in the shallows. and eventually they’ll chase one down and jab down and spear this nice fish out of the water.
The abundance and diversity of birdlife reveals the richness of the habitats found on Louisiana’s barrier islands. For many species their very existence is inextricably tied to these habitats. These birds have evolved over millennia in concert with these subtle features that it’s hard for us to even see.
[Louisiana’s barrier islands are rapidly disappearing. Discover more about the issues at: www.birds.cornell.edu/spill. Explore coastal restoration efforts at: www.coastal.louisiana.gov]
[Cinematography: Neil Rettig, Gerrit Vyn; Aerials: Eric Liner; Still Photography: Gerrit Vyn; Natural Sound Recordings: Michael J. Andersen, Jessie H. Barry, William W. H. Gunn, Geoffrey A. Keller, Thomas G. Sander, Charles A. Sutherland, Gerrit Vyn]End of transcript
Shorebird Foraging Strategies
As many as 30 species of shorebirds migrate to Louisiana’s barrier islands each year. With so many migrants crowding in to join the year-round residents, you might be wondering how all of these birds find enough to eat. The answer is that each species has its own microhabitat as well as its own feeding techniques. For example, the Long-billed Curlew probes deep into the sand to reach burrow-dwelling crabs and shrimp. The small, stocky Ruddy Turnstone flips over shells, pulls through seaweed, and digs in search of little crustaceans and other small invertebrates. Piping Plovers and Semipalmated Plovers have a “run-stop-run” foraging method. They locate prey on the surface by sight, then run over and grab them. The Reddish Egret corrals groups of small fish in the shallows. Eventually, it chases one down and spears it out of the water. Small differences in foraging behavior and beak shape allow each bird species to find its own niche.
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