Pelicans haven't evolved much in 30 million years. That's because they've pretty much nailed how to be a pelican. From KQED:
A number of anatomical adaptions enable the bird to take these dives in stride. The shape of its bill is essential, reducing “hydrodynamic drag” — buckling forces, caused by the change from air to water — to almost zero. It’s something like the difference between slapping the water with your palm and chopping it, karate-style.
And while all birds have light, air-filled bones, pelican skeletons take it to an extreme. As they dive, they inflate special extra air sacs around their neck and belly, cushioning their impact and allowing them to float.
Even their celebrated pouches play a role. A famous limerick quips, “A remarkable bird is a pelican / Its beak can hold more than its belly can…” That beak is more than just a fishing net. It’s also a parachute that pops open underwater, helping to slow the bird down.
“This is a really tough bird that’s built to last,” said (Anna Weinstein, Marine Program Director at California Audubon).
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