Open a carpenter's tool-box and you will find many different sorts of implements. Each of them has been designed for a special purpose. When you visit a museum you will be impressed by the infinite variety of forms of bird beaks. Nature has endowed each bird with a beak suited for the bird's work, which is primarily food-getting. Considering the food of all species of birds, it seems that some bird feeds upon any animal or vegetable substance that we can think of. Thus a great range of different types of beaks is necessary in the bird world, fulfulling very diverse purposes.
The beaks and feet of birds are their implements with which they work for a living, often, indeed, they are weapons of offense, a combination tool-kit and arsenal. Since the bird uses its arms and hands for flying, the beak and feet have developed to take their place as the bird's tools.
Whether the shape of a bird's beak is determined by the food which, in the racial history of the species, it has pursued, or whether fundamentally the bird subsists upon a particular type of food because hereditary factors have given it a beak suited to securing that food, is an interesting question which need not be argued here. Whatever the cause of the result of the evolution of beaks and of food habits, the perfect adaptation between them.
Among birds which live upon animal prey are the birds which fish for a livelihood. Different groups of fish-eating birds have strikingly similar beaks which serve the same function.
For example, the Kingfishers, illustration (#1) Herons and Terns belong to three different Orders, not being at all closely related. Yet they live upon fish and all have long sharp bills suited for spearing fish, though the birds in other respects are very different.
The Hawks are also animal feeders, having strong, hooked bills and powerful talons. Other birds of prey, the Owls (#5) are unrelated to Hawks but have similar beaks and feet, used in the same way. The Vultures were once birds of prey like Hawks, and in becoming scavengers they have kept the hooked, hawk-like beak for tearing flesh, but have lost the strong talons for seizing prey.
The insectivorous birds form a large group representing many diverse habits and forms of beaks, for insects are many and various. Some insects live in the bark or wood of trees, and the woodpeckers bore holes into the tunnels of such in sects. Their long chisel-like beak serves this purpose. Chickadees, Nuthatches and Creepers search diligently into the bark crannies for hidden insects, picking them up with their long slender bills. Flycatchers have a large, broad, hooked beak with stiff bristles at the base, the whole forming an efficient scoop for snapping flying insects from the air. Some insect-feeders live also to a considerable degree upon fruits and berries. The Cedar-waxwing (#3) is such a bird.
The Crow, (#2) with its omnivorous diet, exhibits a generalized type of beak, adapted for a wide diet, both animal and vegetable, rather than being specialized for one sort of food. The large, strong beak is a tool useful for many purposes.
Most birds living on vegetable food live on seeds and have a short, stout, conical beak like that of the Sparrows, for cracking seeds. The Grosbeaks, closely allied to the Sparrows, are represented in Mt. Rainier Nat'l Park by the Black-headed and Western Evening Grosbeaks. These birds show extreme modification of the beak for cracking seeds, their bills are very heavy and strong for such a small bird. The Pigeons (#6) on the contrary have relatively weak bills since the gizzard takes care of the grinding of the grain which forms much of the bird's diet.
Two birds with very unusual development of their beaks in adaptation to peculiar food habits are the Crossbill with crossed mandibles for extracting seeds from cones, and the Hummingbird with its needle-like bill for probing blossoms for nectar.
A. A. Lindsey,
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