The question of whether or not Western Red-tailed Hawks winter on the great plains has been debated for years. Below I detail an anecdote that shows that at least one bird does…
We were surprised to catch the bird below in eastern Kansas last winter. It’s a rufous bird that as far as I can tell, is a Western Red-tailed Hawk (ssp. calurus). Take a look, and compare the bird to the photos of a bird I caught near Boise, Idaho, in July.
Eastern Kansas – February 2020
Southwestern Idaho – July 2020
Westerns, or nearly pure Westerns, do breed east of the rockies in New Mexico, Colorado, Wyoming, etc. The hybrid zone from calurus into borealis hasn’t been properly characterized, but through eBird and the Macaulay Library we are beginning to get a broad picture of this cline. Consider the pattern at the Colorado contact zone. We know that borealis breed to the front range in Colorado (with influence likely entering the range in some areas), and interbreed with calurus throughout the region. One the other end, Kansas is yet to have a clearly documented breeding calurus in the state, although Luke may change that, but that is his story. The point is, calurus influence largely fades out before the border between Colorado and Kansas.
Could the rufous bird we caught come from an area like the Colorado contact zone? Could it have originated from intermountain region? Or could it come from further north within the distribution of calurus in British Columbia?
At the moment, we don’t have the answers for these questions, but we can find out by scaling up our transmitter effort!