On hot, summer days, bird song is generally subdued. The high-pitched twitter of chimney swifts, brief tunes from the ever-cheerful chickadees and the buzzy chatter of house wrens are some of the few calls that pierce the oppressive heat. But, as is always the case in nature, there are exceptions.
This summer, a flock of lesser goldfinches has settled at our Littleton, Colorado, farm for the first time. Common across the foothill canyons and shrublands, they are much less common on the adjacent Piedmont and we are about five miles from the base of the mountains. For the past few days, the colorful males have been singing from dawn to dusk, indicating that their breeding season is underway. Like their cousin, the American goldfinch, this western species nests in the summer, timing the process with the peak availability of favored seeds (especially thistle); they also use thistle down to line their cup-shaped nests. While adults feed on both seeds and insects, the nestlings rely on a fresh crop of soft, immature seeds (hence the importance of timing).
Most species that inhabit hot, dry environments concentrate their activity during the morning and late daylight hours, retiring to cool, shaded areas during the heat of the day. But when breeding season arrives, these finches seem oblivious to the conditions; some instincts are stronger than others!
