Oklahoma Breeding Bird Species Profile: Tree Swallow

https://phys.org/news/2017-11-birds.html

These common birds nest in nestboxes or tree cavities over water or in open fields, where they will also forage for insects or berries.  They are the only swallows that can eat berries and seeds over a lengthy time period, which is why they can overwinter in the Middle Atlantic states.  They are found nearly everywhere there are large open populations of insects.

Like Purple Martins, Tree Swallows hunt in flight and pull insects from the air.  They will hunt over marshes in groups, then roost communally at night.  They breed in colonies where nest sites are available and associate with other swallow species.  Their song is a simple gurgle.

They prefer cavities in dead trees or snags, as long as it is over or near water.  The female builds a cup nest and usually lines it with feathers for her four to six eggs.  The male will watch the eggs, but he will not incubate them.  Both sexes will feed the young.

                                                                      Tree Swallow
                                                                   Red Slough, 2016

These songbirds are usually on the breed grounds between March and May.  Fall migration begins in July or August, with peaks in September or October.

A recent study shows that birds in agricultural areas are working harder to capture preferred prey.  Due to preferred food over wetlands and insecticide use, it was suspected that they could be shifting over to terrestrial protein.  That turned out not to be the case, for agricultural resident birds tended to weigh less overall.  Diet quality was much better in unadultered grassland as opposed to insecticide laden cropland.

Tree Swallows usually nest in the same area each year, but they may disperse if the nesting year is poor.  The male will attack the female during courtship, and she may wing-flutter to encourage subsequent behavior.  The male will hover over the female, and he will stand upon her wings to make cloacal contact, which holding her neck feathers in his bill.  Then he will bring her to the nest site, where they will raise and tend young.  She is dependent upon food sources and the weather to determine when she will begin laying eggs.

Diet is mostly flies, but they will also take seeds, berries and mollusks.

Genetics and Tree Swallows:

https://debhirt.blogspot.com/2017/11/an-inside-look-at-tree-swallow-research.html

Tree Swallows and the Birds of McCurtain County:

https://debhirt.blogspot.com/2016/05/the-birds-of-mccurtain-county-oklahoma.html