Swallows are small to medium-sized songbirds that mainly eat flying insects. In Central Texas, we have seven regularly expected species. Five species breed in the Austin area. They are joined in the fall months by their northern relatives heading south for the winter. All are heeding nature’s call to leave before the insect prey they depend on are depleted. (Swallows are at risk for starvation and hypothermia in the event of a severe early cold front.)
Most Purple Martins leave the Austin area by the end of August. Most Cave and the similar Cliff Swallow are passing through now, and will be thin on the ground in October. Ditto for the Northern Rough-winged Swallow. Barn Swallows migrate through in August, September and early October, with stragglers in November. The sixth and seventh species, Tree and Bank Swallows, don’t typically breed in Austin, although both are expected breeders in central Texas. Tree Swallows appear in the migration window of September and October and Bank Swallows in August and September, with most observations of Bank Swallows in September.
Bank Swallow – the smallest North American Swallow
The Bank Swallow is tiny, at 5.25 inches in length. It’s a study in shades of brown, with a brown head, back, wings and tail. These muted colors contrast with clean white underparts and a white throat that highlight the brown breastband, a diagnostic feature. Sometimes the breastband has a ventral stripe that goes down to its belly, too. Its wingbeats are characterized as quick and fluttery. The Bank Swallow often makes a distinctive repetitious electric buzzy “chirr” sound.
While Bank Swallows do breed in a few locations in south and central Texas, they are mostly birds of the northern U.S., Canada and Alaska. Bank Swallows are colonial nesters, with documented colonies in the U.S. of less than 10 to 2,000 active nests. They nest in the varied types of friable soils of river and lakeshore banks, bluffs and cliffs. Amazingly, they do this by tunneling into the banks using their bills, feet and wings to excavate a burrow about 20 to 39 inches in length. After the burrows are complete, the mated pairs build nests at the back and the females start their broods. Deeper nest burrows are associated with higher nest success. The most sought-after nest sites are situated just under the top of the banks. These are safer from collapse and predators like snakes than those at the edge of the colony or lower down the bank…