Bird's bill helps tell what it is-10/3/99-BYLINE: GARY CLARK; Gary Clark is associate dean of Natural Sciences at North Harris College and a free-lance writer. Kathy Adams Clark is a professional nature photographer who also teaches photography courses for North Harris College and Leisure Learning.
You can't tell a book by its cover, but you can tell a bird by its bill. When you see a duck, you know it's a duck mostly because it has a duck's bill, right? Pelicans have pelican bills, hawks have hawk bills and woodpeckers have chisels for bills. People instinctively identify birds by their bills.
The shape of a bird's bill helps you classify the bird in the right family. You could instantly place a pelican in the right family (Pelecanidae) because of its huge, pouched-shaped bill. You recognize a cardinal (subfamily Cardinalinae) by its stubby, conical-shaped bill. Anyone who has strained his neck looking up into treetops trying to tell a warbler (family Parulinae) from a vireo (family Vireonidae) will tell you that the bill structure quickly distinguishes the two families.
Bird bills may be long and curved, long and straight, short and curved, short and straight, broad, pointed, hooked, flattened, bulky or dainty. In birds, the form of the bill follows its function. The function of the bill gives you a big clue about how the bird earns its living. If you know how the bird earns its living, you'll know what family it's in. Once you know that, you'll likely identify the species of bird.
A pond duck's bill is long and flat. Pond ducks bob their heads under water to sift food out of the water with their specially adapted bills. Birds that earn their living this way are called "dabbling ducks" and include an easily recognizable species, the mallard. The edges of a mallard's bill have a series of ridges called lamellae that enable it to seine shallow water for animal and vegetable matter. Sensitive nerve endings along the bill's edge, similar to nerve endings on human fingers, help the mallard "feel" seeds and animals in muddy water. Mallards and all other ducks belong to a larger family of waterfowl called Anatidae, which also includes geese.
Geese have a flattened bill, too, but it is generally more arched and rounded than a duck's bill. A goose's bill differs slightly from a duck's because geese earn their living mostly in fields, not ponds. Geese, being vegetarians, tear out roots and tubers in the ground. Their bill, therefore, is stouter and has sharper lamellae than a duck's bill. This winter, when thousands of snow geese arrive on the Katy prairie, go out and take a close look at their bills.
Take a look at the birds in your back yard. The tiny little Carolina wren has a long, downward-curved bill that's thin and pointed. It earns its living by probing for insects and spiders in the cracks and crevices of your patio or fence line. The bright red cardinal earns its living by eating things like grass seeds, beetles, snails, berries and grain. It has a short but powerful conical beak that operates like a nutcracker. A cardinal places a seed in the groove of its upper mandible and then crushes it with the sharp edge of its lower mandible. Cardinals shuck beetles just like they shuck seeds.
Woodpeckers earn their living by chipping away tree bark to get at the variety of arthropods underneath. Their bill is shaped like a round chiseling tool used to mill out wood. Woodpeckers mill out wood, but they do it by hammering on a tree, not by gouging. Skull muscles that form a kind of sling for the bill absorb the impact of all that hammering.
A hawk's bill is fearsome. The robust upper mandible curves downward at the tip into a sharply pointed hook. Hawks catch prey with their talons and then tear it into edible pieces with the shearing action of the upper, hooked mandible. Falcons, like the peregrine falcon, have teethlike notches on the cutting edge of the bill used to break the necks of prey.
Loggerhead shrikes are small birds the size of mockingbirds that have a bill similar to hawks'. The bill has a sharp hook on the tip of the upper mandible. Shrikes impale a captured lizard or grasshopper on a thorn bush or barbed-wire fence. They may also wedge prey into the fork of a bush. Later, the shrike returns to the impaled carcass and rips the meat to pieces with its hooked bill. This indelicate style of eating gave rise to the shrike's folk name, "butcher bird."
All bird bills are merely projections of the upper and lower jaw. The upper projection is called the upper mandible, the lower projection the lower mandible. A horny sheath of keratin - the substance of fingernails - covers the bill. Mandibles usually have sharp edges and a hardened tip. The tips of bird bills wear down with all the pecking, crunching and tearing they do. But the bill's tip is continually renewed by the regeneration of keratin, in the same way that human fingernails grow.
Most bird bills are darkly colored throughout the year. But a bill like that of a puffin is the most strikingly colored part of the bird. Also, the color of a gull's bill helps bird-watchers determine whether the gull is an immature or an adult bird. Some bird bills change color during the breeding season. The American robin has a yellow bill in breeding season and a dark bill in nonbreeding season.
Start classifying birds according to the shape and structure of their bills. Think in terms of duck-type bills, hawk-type bills, and so on. Look in your bird identification field guide and notice how many bird names are derived from the character of the bill - for example, pied-billed grebe, long-billed curlew, spoonbill, yellow-billed cuckoo, broad-billed hummingbird, long-billed thrasher, and the probably extinct ivory-billed woodpecker. Bird-watchers not only tell a bird by its bill, they often name it by its bill.
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