A significant number of birds depend on fish as part of, or all of, their diet. Catching a fish is only part of the challenge. Once caught, the bird must keep other birds or mammals from stealing the fish before it can be consumed.
Next, the fish has to be repositioned before swallowing it whole. If you have handled a fish before, you know to slide your hand from the head to the tail when grabbing it. Otherwise, the dorsal fins can prick you. Birds swallow the fish head first so that the fins do not get caught in their throat. The trick is to not lose the fish in the process.
After properly positioning the fish, the bird must try to swallow it. If the fish is too big, the bird eventually tires and lets the fish go. It is truly amazing how big of a fish a bird can swallow.
Belted Kingfishers perch or hover above the water and dive down to catch their prey. Then, they fly to a perch, pound the prey against the perch to stun or kill it, and then swallow it whole.
Bald Eagles take a little different approach. They usually perch or fly over a water body, spot a fish, pick it off of the surface, and continue their flight to a perch or nest. Then, using their sharp beak and talons, they rip the fish into pieces to be consumed.