The Tree Swallow is a handsome aerialist with deep-blue iridescent backs and clean white fronts.  They chase after flying insects with acrobatic twists and turns.  They migrate south to us in the winter.  Migrating Tree Swallows can form enormous flocks numbering in the hundreds of thousands, forming a dense cloud above a roost site.  They get their name from their habit of nesting in tree cavities.

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The female does most of the nest building, taking from a few days to two weeks to build the nest.  The nest is small, about 2-3 inches across and 1-2 inches deep.  It is made mostly of grass but may include pine needles and may be lined with feathers.  They and 1–2 broods a year with 4-7 eggs.  Incubation is 11-20 days with the nestling period 15-25 days.  At hatching they are helpless, with closed eyes and pink skin sparsely covered with down.
 

Tree Swallows eat mainly insects but may add berries and during the breeding season when they need extra calcium, may eat fish bones, clamshells, and other high-calcium items.  They chase their prey in the air, with acrobatic twists and turns, feeding from dawn to dusk in sheltered areas full of flying insects.

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Tree Swallows are highly social and bathe by flying low over the water and skimming their bodies against the surface, then rising quickly while shaking off droplets.   The oldest Tree Swallow on record was 12 years, 1 month.  They are of low conservation concern, but natural tree cavities for nesting have been disappearing as people clear the land and cut down older trees.  They may also ingest pesticides due to the high insect diet.