Until a recent study, it was common knowledge about bird beaks were about eating rather than for mating. Interestingly, many analogies using birds have reference to mating in general, such as in a cliché, “birds of a feather flock together,” or “the birds and the bees” and so forth.
Researchers Russell Greenberg, Matthew Etterson and Smithsonian scientist, Raymond M. Danner from the Smithsonian Conservation Biology Institute (SCBI) recently published their findings in Ecology and Evolution show beaks grow larger during breeding season to attract a mate or for fighting.
The bird’s beak has a horny covering performing much like the horns on cattle, goats and other animals for example whose males have larger horns than female animals; therefore, the male Sparrow’s bills grow proportionally more during its’ breeding season than females.
Different from a skeletal system, the horny bills are made of keratin, a fibrous in soluble protein and main structural element in bills; therefore, they grow, wear and vary in size throughout a bird’s life, much like fingernails on humans or hooves on various animals.
“Traditionally, we’ve viewed bill size in terms of how it helps birds eat,” said Russell Greenberg, head of SCBI’s Migratory Bird Center and paper co-author.
“By looking at the infrastructure of bird bills using X-rays, we discovered that male bill sizes change seasonally, suggesting that bills play a role in mating and fighting as well.
What’s also interesting is that we combined technology and this expansive bird collection to conduct this first-of-a-kind study, which is helping us better comprehend why birds have different beak sizes and shapes.”
Subjects studied were two groups of tidal marsh sparrows, which were chosen due to their horny bills, varied more in size between the sexes. Finding the beak is smallest in late autumn and in the late spring to early summer growth is to its’ maximum size, which is the breeding season for the species.
The Smithsonian Conservation Biology Institute (SCBI) plays a key role in the Smithsonian’s global efforts for protection of all species by educating future generations of conservationists. In order to save a species SCBI must grasp how mating happens; therefore, if size matters they need to know.
Headquartered in Front Royal, Va., SCBI facilitates and promotes research programs based at Front Royal, the National Zoo in Washington, D.C., and at field research stations and training sites worldwide.