UNT researcher notes kestrel plumage varies

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Text by Paula Dittrick, TMNCPC blogmaster, based upon Jan. 19 Facebook post by Kelsey Biles on UNT Raptor Research Facebook. Photos by Kelsey Biles.

American Kestrel populations are in decline, prompting researchers to study if the decline can be primarily attributed to their wintering ground or during migration.

Kelsey Biles, a University of North Texas Ph.D. student, is working with the UNT Raptor Research program to track Kestrels in Denton and Gillespie counties.

She has trapped Kestrels over the past three winters. Recently, she reports that Kestrels show “amazing variation” in their plumage, particularly on their tails. Plumage variation also has been reported by researchers in other states.

Kestral tail
American Kestrel caught in Denton during January. Researchers noted lack of red in the tail, the barring, and the pointed ends. Photo by Kelsey Biles, UNT Raptor Research.

In a UNT Raptor Research Facebook posting on Jan. 19, Biles shared several photographs. She agreed the photos could be used for this Texas Master Naturalist Coastal Prairie blog.

Spots throughout the tail are unusual. Photo by Kelsey Biles, UNT Raptor Research.

“Plumage polymorphism, where multiple forms of a trait are maintained within a species, is widespread among many families of birds, but is especially common in birds of prey,” Biles said. “The factors that influence kestrel tails are complex, but researchers believe that the variation seen isn’t directly due to sexual or natural selection.”

Here is another distinctive plumage pattern. Photo by Kelsey Biles, UNT Raptor Research.

The American Kestrel Partnership, a project of The Peregrine Fund, supports Biles’ research by providing tracking devices to provide data on overwinter survival, annual survival, and migratory paths for kestrels that spend the winter in Texas.

A portion of UNT’s research was featured in a National Audubon Society article.