The primary food of birds that depend on water bodies is fish, though they also take on snails, crabs, crustaceans and amphibians. Some also eat snakes. They adopt various strategies to catch their slippery and streamline-bodied prey.
1. Shadow and Seduce:
Certain types of herons and egrets form their wings like an umbrella over water. The fish when feel tired or threatened go to the shades thinking that they are rock crevices and can hide in them. However, the shadow is of the predator and therefore fall prey to the waiting beaks.
In picture: Juvenile night heron (though not in classical umbrella pose)
2. Dip and Dig:
Openbill storks use this strategy to catch the snails (for themselves) and fish (for their young). The keep the beak inside water disturbing the mud and grab any creature that is perturbed!
3. Fly and Flick:
The fishing eagles fly over the water and flick the fish out with their talons. The talons are supported with toes that have serrated scales in the underneath to ensure the slippery meal does not slip away.
In picture: Primary weapon of fishing eagle – its talons
The skimmer on the other hand has a longer lower beak which is used to skim over the surface of water. Anything that can be touched by the lower bill can be eaten.
4. Clasp and Grasp:
The spoonbills keep their flattened spoon-like beaks inside water and keep wading. Once something comes between the beaks, the prey is clasped and the gobbled upon. The similar strategy is used by snapping turtles, alligators and gharials.
In picture: Spoonbill