Late this morning, my wife and I hiked around Hines Lake at Robert Eastman Park; this park is in southwest Metro Denver, near the foot of the Dakota Hogback. On our lakeside hike, birds were rather sparse; sightings included a lone cormorant, several common mergansers, mallards, pied-billed grebes, red-winged blackbirds and a few ring-billed gulls.
Climbing back to the parking lot, however, I watched as waves of Townsend's solitaires moved from the foothills onto the Colorado Piedmont, funneling eastward through a break in the Hogback. Their annual vertical migration was likely accelerated by cold rain and snow in the upper foothills and mountains that began yesterday afternoon and ended this morning. Indeed, after breeding in open coniferous forest, Townsend's solitaires move to the lower foothills and Piedmont each autumn, switching from a mixed diet of insects and berries to a strict diet of juniper berries.
Once settled in for the winter, the solitaires are highly territorial, defending their berry cache from one another (though they still must contend with robins, waxwings and other berry consumers). Our resident solitaire arrived on the farm several days ago, delivering his high-pitched call from the top of a large honeylocust. Just yesterday, I watched as he chased another solitaire from the property, ensuring an ample supply of berries to survive the winter.
