WINGS IN FEEDING [Ref]
The obvious adaptation of a bird's wings is for locomotion; to fly in the air. It is true that some few birds are flightless, and some like the penguins use their wings for underwater swimming, but this does not spoil the generalization.
Secondary uses, some with special adaptations, occur: the owl at bay spreads its wings wide, with the effect of increasing its apparent size and being more terrifying to a predator. The young bird, begging to be fed, flutters its wings in a characteristic way, and the female, in some of her mating behavior, may also flutter her wings like those of a young bird.
In courtship the wings may play an important part in display. In the Australian rifle bird they are held out, fully spread on each side of the bird like a velvet curtain against which the vivid iridescence of the throat patch stands out more vividly. The argus pheasant has the inner secondaries greatly elongated and ornamented in a fashion recalling the decoration of a peacock's tail and these he spreads to show in his courtship, while the ruffed grouse uses his wings to make instrumental music, his drumming.
Wings in geese and swans may be used in fighting, and tame birds may severely buffet humans who take too close an interest in their young. In the related screamers of South America the bend of the wing is equipped with long, very sharp spurs, which undoubtedly make formidable weapons in fighting.
In addition wings are used in at least three different ways in feeding. The red-tailed hawk may spread its wings as it sits on its prey, perhaps a behavior adapted to help the bird maintain its balance when dealing with struggling prey, perhaps to help smother the struggles of its prey.
The secretary bird of Africa is said to feed on snakes, poisonous and non-poisonous ones, and is said to use its huge wings as shields for its body in attacking them.
But the strangest use of wings in feeding is that practiced by a blackish African heron. In feeding in shallow water it takes a few rapid steps, apparently to bring it within reach of fish it has sighted, then spreads its wings, bringing them forward until they meet, and with the tips of the quills in the water. The head is in the canopy formed by the wings, and apparently it is here under this canopy that the fish on which it feeds are caught. The suggestion as to the correlation that presents itself is that the dark canopy thrown over the fish confuses them and makes them easier to catch.