Tree swallows spend the winter along the Gulf Coast, across Florida or in Mexico, much farther north than their cousins (barn, cliff, bank, violet-green and rough-winged swallows). As a result, they arrive on their summer breeding grounds much earlier, generally by mid-late March.
Yesterday, I observed a small flock of tree swallows at South Platte Park in Littleton, Colorado, the first I have seen this season. Strafing clouds of midges that hovered above the ponds, the swallows had likely hitched a ride on recent southerly winds that brought summer-like weather to the Front Range. Soon they will pair off and locate a cavity (in a tree or nest box) in which the female will build a nest of dried vegetation.
Arriving in Colorado well before the end of our snow and ice season, tree swallows risk annihilation of their primary food source. Fortunately, these aerial insectivores can expand their diet to include other invertebrates or plant material if necessary. Nevertheless, one must admire their courage and optimism, even if it is instinctual.
