Anhingas are waterbirds with no buoyancy. In other words, they are bad floaters. Think of yourself, arms open, staring at the sky, floating in the ocean. You tend to sink. Much like an anhinga.
Anhingas feathers are not water tight. The tiny spaces between feathers and skin get waterlogged. That makes them heavier in water. That is why anhingas float with their whole body submerged. This is not great when floating.
Firstly, it cools your body temperature quickly. It also takes more energy to keep afloat.
Finally, it makes it harder to take off from water.
Why would a water bird want this anatomy?
Here is why...
- Bad floaters are good sinkers. Good sinking is great when diving. That is true whether you come in from the air or from water. So anhingas consume less energy below water than other watertight birds.
- They can also dive deeper. This expands their fishing range. They can get to fish other birds can´t.
- Waterlogged feathers, however, also mean tightened their range around the tropics. They need lots of sun to dry off cold water. They also need to avoid freezing temperatures.
As always –the link to the paper.
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