Bird of the Month by Russ Chappell
Agile aviators, tree swallows prey on flying insects near fields and wetlands, their blue-green feathers flashing in the sun.
When not flying they perch on utility wires and shrubs, scouting for prey. A vocal species, you can often locate them by their cheerful chirping calls while pursuing insects.
They are streamlined songbirds with pointed wings, short, squared or slightly notched tails and black bills, nearly six inches long with wingspans reaching over 13 inches. Males have blue-green backs and white fronts, dark flight feathers and thin black eyemasks, females are duller, with brown upper parts, and juveniles are completely brown above.
They supplement a primary diet of insects with berries from fruit-bearing shrubs, and prior to breeding may visit backyard compost piles looking for eggshell to add calcium to their diet. Named for their custom of nesting in tree cavities, they are also attracted to nest boxes, allowing scientists to make them one of the best studied species in North America. Note: if you install a nesting box, attach a guard to restrict access to the eggs and young. Nest predators include snakes, raccoons, bears, chipmunks, mink, weasels, mice and cats. During migration and non-breeding periods they live in the open, without nests or nesting boxes. The female may complete her nest in a few days or as long as two weeks. It routinely consists of grass, pine needles, mosses, rootlets, aquatic plants, animal hair and materials like cellophane or cigarette filters, and is lined with feathers from other bird species, usually provided by the male. Parents share nesting duties evenly. A clutch consists of four to seven pale-pink eggs that fade to white in three or four days. Incubation takes up to 20 days, with chicks hatching helpless, eyes closed, their pink skin covered with down, and able to leave the nest in 15-25 days. Not on the 2014 State of the Birds Watch List, and rated eight out of 20 on the Continental Concern Score, tree swallows are not considered endangered.
The Prescott Audubon Society is an official chapter of the National Audubon Society. Check it out online at PrescottAudubon.org.