North Words - The many shapes and sizes of bird beaks
Beaks or bills, whatever you want to call them, are among the most diverse body parts found on creatures the world over. Designed for procuring food, masticating, and working food bits into the mouth and swallowed, there are few other orders of organisms -- save for insects -- that have mouth parts more varied.
In the world of birds, bills (or beaks!) come in all shapes and sizes. Beaks are often quite handy for identification purposes too. As in some birds, such as species of crossbills, bills are a diagnostic trait. In all cases, the many different beak sizes and shapes evolved in relation to the types of food eaten.
This past October while enjoying the spectacular expanse of a mountain sunrise as I sat beneath a stately old lodge pole pine tree hunting deer, I was as thrilled by not only the setting as I was with the small band of fifteen or so red crossbills descended into the canopy of a nearby lodge pole.
Their noisy chattering was interspersed with the sounds of their highly specialized beaks prying open the scales of tennis ball-sized cones to extract the nutritious pine seeds. Once in awhile a bird would dislodge a cone from its lofty mooring and down the cone would come with a resounding thump onto the Colorado red dirt and assorted rock.
I watched the foraging birds in spellbound fascination much like, I suppose, the renowned naturalist Charles Darwin once did. Darwin, author of "On the Origin of Species by Means of Natural Selection" (1859), used the beaks of birds (among other physical characteristics too) to help determine species' relationships and his eventual concept and 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 beaks a species of finch possessed seemed to be related to not only the types of foods a species exploited, but where in the environment the bird was found.
Differences in beaks are not apparent amongst species, but it's a different story between species. All hairy woodpeckers have the same size and shape bills. There just isn't any notable variation. However, a similar looking but different species, the downy woodpecker, has a proportionately much smaller beak than the hairy's.
These two species of woodpeckers are found occupying similar habitats with each other, but do not seem to be competing with one another for the same resources. Indeed, aggression between these two species of birds when confronted with one another appears nonexistent. And if you look closely, you will notice that not only is the downy much smaller in body size to the almost identical looking hairy, but its beak is much smaller too.
The bill, of course, is first and foremost a tool for gathering and consuming food. In the case of downy Vs hairy, beak type is in direct relation to food type. The hairy's more robust and larger beak enables it to exploit food sources that may not be readily available to the downy. Conversely, the downy's diminutive size, including its tinier bill, probably is better suited for finding smaller insects in smaller places.
This example is repeated over and over in birds. In Africa where more than one species of vulture exist together in the same environment, it is beak size and shape that, along with body size and strength, work in unison to determine what part of the carcass a particular vulture feeds on first. While species dominance plays a role in this case, 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 wherewithal to open up a fresh carcass, which in turn makes the carcass more accessible to other species.
While you observe Minnesota's resident birds at your feeders, take note of the many and different beak designs out there. Ruby-throated hummingbird's bills are perfectly designed to probe for flowers' nectar, in addition to those tiny holes in hummingbird feeders. The unusual beaks of the red and the white-winged crossbill are used to pry apart the scales of pinecones while their tongues extract the seeds. Species of grosbeaks and finches have large, conical-shaped beaks that are powerful seed crackers.
And the list goes on. Species of 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 beaks designed for ripping flesh from their prey.
Many shorebirds, including the American woodcock, have long and narrow beaks that are primarily used to probe soft soils in their search for insects and other prey items. Nearly all species of warblers have straight, slender, and pointed bills. Beaks of these designs are ideally adapted to foraging for insects, their principal food.
Even ducks, with beaks that to most people seem quite the same, have many differences. For example, the northern shoveler, so named for its unusually large shovel-like beak, is also equipped with rows of lamellae (comb-like structures) inside its beak that help to filter from water, mud, and plants, such food as aquatic insects, snails, and various plant material.
The beaks of birds (or bills!) are just one of the many and fascinating wonders found in nature. Their variable designs have all evolved to equip each species of bird with unique abilities to forage on particular foodstuffs and manipulate myriad items. Indeed, possessing knowledge of bills or beaks will provide endless discoveries as we get out and enjoy the great outdoors.
(Klemek is the DNR Area Wildlife Supervisor in Detroit Lakes. You can contact him at firstname.lastname@example.org)