The bills of birds come in all shapes, sizes and colors. Primarily used to find and gather food, bills are used to probe mud, to peck wood, to tear flesh, to sift water, to pry seeds, and much more. Bills are used as weapons, to produce special sounds, to carry nest material, and even to pollinate plants.
Fortunately for us, bills can also be used for identification. For some birds, such as crossbills, bill design is a diagnostic trait. In other birds, like yellow-billed magpies and black-billed magpies, bill color is the obvious difference between the two otherwise identical species. Yet in all cases, the many different sizes and shapes of bills have evolved in relation to the types of food eaten.
Charles Darwin first used the bills of birds to help determine species' relationships and his eventual concept of the theory of evolution. On the Galapagos Islands, Darwin observed that different species of finches had different types of bills. Further still, the naturalist noticed that the kind of bills a species of finch possessed seemed to be related to not only the types of food resource a species exploited, but also where the species of bird was found within its environment.
Differences in bills are not normally apparent amongst birds of the same species, although bill differences do exist between the sexes of some species. However, it's a different story between species. To illustrate, all hairy woodpeckers' bills are the same size and shape. There just aren't any notable variations.
On the other hand, a similar looking but different species, the downy woodpecker, has a proportionately much smaller bill than the hairy's. In this case, bill type is directly related to food type. The hairy woodpecker' robust, large bill enables it to take advantage of food sources that might not be accessible to the downy. Conversely, the downy woodpecker's small size, including its tinier bill, is probably better suited for finding smaller insects in smaller places.
Similar examples occur frequently in birds the world over. In Africa, where more than one species of vulture exist together in the same environment, bill size and shape, along with body size and overall strength, work together to determine what part of a carcass a particular species of vulture feeds on first.
When different species of vultures gather at the same food source at relatively the same time, it is the stronger and larger species of vulture that, along with their powerful bills, has the ability to open up a fresh carcass, which in turn makes the carcass more accessible to other smaller species with smaller bills.
While you observe Minnesota's resident birds at your feeders, take note of the many and different bill designs out there. In addition to the tiny portholes of hummingbird feeders, ruby-throated hummingbird's bills are perfectly designed to probe flowers for sweet nectar. The unusual bills of crossbills are used to pry apart the scales of pinecones while their tongues extract the seeds. Species of grosbeaks and finches have large, conical-shaped bills that are powerful seed crackers.
Swallows, nighthawks and whip-poor-wills have short bills but very wide mouths that enable them to more easily capture flying insects. Most hawks and eagles are outfitted with heavy, hooked, and sharp bills designed for ripping flesh from their prey.
Many shorebirds, including the American woodcock, have long and narrow bills that are primarily used to probe soft soils as they search for insects and other prey items. And nearly all species of warblers have straight, slender and pointed bills. Bills of this design are ideally adapted to foraging for insects, their principal food.
Even ducks, with bills that to many people appear similar to other species of ducks, have many differences. For instance, the bill of the northern shoveler, so named for its unusually large shovel-like bill, is equipped with highly developed rows of comb-like structures. These structures, called lamellae, help filter out food particles from water and mud.
These curious looking ducks with their spatulate-shaped bills dabble along the surface of the water sifting out mostly animal material, or by "shoveling" in soft mud. The feeding style of the northern shoveler has been described as ". . . straining out its food much after the manner of a right wale."
The bills of birds are just one of the many and fascinating wonders found in Nature. Their variable designs have evolved to equip each species of bird their own unique ability to forage on particular foodstuffs.
From the enormous bills of puffins to the lengthy bills of long-billed curlews, and from the dagger-like bills of loons to the highly specialized bills of hummingbirds, knowing and observing these interesting avian structures is only part of the fun as we get out and enjoy the great outdoors.
Blane Klemek is the Bemidji area assistant wildlife manager, DNR Division of Fish & Wildlife. He can be reached at firstname.lastname@example.org