A Bird of a Different Feather: DNA Research Reveals New, Yet Familiar Species

Bird of A Different Feather

In the sagebrush ecosystem of southwestern Colorado and southeastern Utah, a new species of bird has been discovered. Formally, the new species will be known as Centrocercus minimus because of its relatively small size, but for many it will be the Gunnison Sage-Grouse, named for the area of Colorado where it was discovered.

The Gunnison Sage-Grouse is not a particularly secretive bird, neither a tree-dweller nor a night bird, and is roughly the size of a chicken, yet just recently did it achieve species status.

Historically, scientists had believed that the Gunnison Sage-Grouse was the same species as the Greater Sage-Grouse, which can be found in northern Colorado and throughout 11 western states and two Canadian provinces. But over the years, differences in body size, unique plumage, and behaviors led scientists to question this kinship. Compiling the evidence needed to formally designate a new species is no easy task, and the final confirmation drew on the growing field of conservation genetics and involved a detailed DNA analysis of the two groups of grouse.

Dr. Sara Oyler-McCance, a conservation geneticist with the U.S. Geological Survey, collaborated with a number of other scientists in the genetic studies that ultimately supported the new species designation. Because evidence of reproductive isolation is one criterion by which species designations are made, the researchers used mitochondrial sequence data and microsatellite markers, among the most powerful molecular genetics markers, to determine whether gene flow, or interbreeding, had occurred between the two groups of sage grouse. The studies concluded that gene flow between the two grouse was absent and corroborated behavioral research suggesting the grouse are reproductively isolated.

The studies also confirmed that most populations of the newly named Gunnison Sage-Grouse are geographically and genetically isolated from each other, with consequent low genetic diversity, factors that can contribute to species decline or extinction. Although the past abundance of this grouse species in not precisely known, scientists have used historical documents and interviews to estimate that Gunnison Sage-Grouse abundance was several orders of magnitude larger than at present and that the species occurred over a much larger geographic area. Now, however, these small grouse, with their penchant for eating sage, are restricted to 8 isolated populations in Colorado and Utah with a total population of less than 5,000. Some populations are small, fewer than 150 breeding birds, and several former populations have become extirpated since 1980.

In January 2000, the U.S. Fish and Wildlife Service was petitioned to list the Gunnison Sage-Grouse as a federally endangered species because of concern that the species is at risk of extinction due to habitat loss, fragmentation, and degradation. Meanwhile, federal, state, and local groups have come together to develop locally supported conservation plans. These plans identify ways of improving grouse habitat, and many consider translocating the Gunnison Sage-Grouse within southwestern Colorado to mimic natural gene flow, with the effect of increasing genetic diversity in some of the small, isolated populations.

Despite differences in their specific methods, for many of these plans the ultimate goal is the continuation of a ritual - a seasonal ritual the Gunnison Sage-Grouse have been going about for eons, unconcerned about their species status - the males gathering together in spring to impress the discerning females with their booming from bright yellow air sacs and their strutting and hopeful dances; the females, who after choosing a lucky suitor, are left to raise their young through the mountain summer and fall.


Plumage comparison between the Gunnison (left) and the Greater (right) Sage-Grouse. Artwork by Deanna L. Rieden.

A Bird Of A Different Feather: DNA Research Reveals New, Yet Familiar Species