In Colorado, violet-green swallows breed in the canyons and open woodlands of the foothills and lower mountains, placing nests in tree cavities or in rock crevices. After wintering in Central America, they generally return to the Front Range in May but often find that it is too cold or snowy in the higher terrain to support their insect diet.
Thus, like some other species (western tanagers, for example), they tend to hang out along the urban corridor for a week or two. This morning, a flock of twelve violet-green swallows performed their aerial maneuvers over our Littleton farm, joined by a pair of tree swallows. Though the recent heavy rains have subsided, we continue to experience cool, cloudy, showery conditions and the mountain snow-line remains rather low.
On chilly May mornings, massive flocks of these migrants often congregate along the South Platte River and its adjacent lakes and wetlands, strafing the relatively warm water surface for flying insects and resting in trees or on power lines. A warm-up is expected over the next two days and many will likely end their layover on the Piedmont.
