The Great Blue Heron
Feeding Habits
 The
Great Blue Heron feeds mainly on small fish less than half the length
of its bill, or under 65 mm long. Shellfish, insects, rodents,
amphibians (mostly frogs), reptiles, and small birds are also
occasionally eaten.
The Great Blue Heron has two principal fishing techniques. The first
consists of standing motionless, its neck extended at an angle of
about 45 degrees to the water surface. Only its head and eyes move to
locate the prey. If no fish comes within range after a few minutes,
the heron gradually moves a short distance away and takes up a similar
position. When a potential meal comes close enough, the heron slowly
folds its neck back and moves one leg in the direction of the prey.
Suddenly, its entire body unbends, its head plunges into the water, it
catches the prey in its bill, and it swallows it outside the water,
using a deft movement of the head to drop the prey headfirst into its
gullet.
Using the second technique, the heron slowly wades around in about
15-25cm of water until it drives a fish out from its hiding place. The
heron then stops and slowly stretches its neck.
 When
the prey is within range, the bird uncoils its body and thrusts its
head into the water after it. After eating the catch, the heron
resumes its walk. Should the bird fail to find sufficient fish in an
area, it flies a short distance away and resumes fishing.
When its catch is too large to be gulped down immediately or has
dangerous spines, the heron drops it back into the water and grabs
hold of it repeatedly and violently with its beak until it is dazed or
the spines snap. Then it can be swallowed more easily. Sometimes two
fish are caught simultaneously.
Other techniques are observed more rarely: for example, Great Blue
Herons in flight some times dive underwater to catch fish; others
hover over the water and submerge their heads to catch fish; and some
swim in deep water and feed on fish found near the surface.
Source: Hinterland's Wildlife
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