Bank Swallows

Riparia riparia

Riparia riparia is the Bank Swallow’s scientific name. Given that it nests in stream banks and bluffs of rivers and streams, i.e. riparian areas, the name is appropriate.

The Bank Swallow is one of the most widely distributed swallows in the world. It nests around the globe at latitudes equivalent to the middle of the US and north into lower Canada and to the Brooks Range of Alaska. For the western hemisphere, it winters in South America down to middle of Chile and Argentina. In the Eastern hemisphere, where it goes by the common name of Sand Martin, it nests across Europe into Russia then winters in several countries of Africa and Southeast Asia.

Bank Swallows are small in the swallow world.  Their length is about 5 1/4 inches, with a wingspan of 13 inches.  They weigh only about half an ounce.  The sexes are similar in appearance and there is little change in plumage throughout year making for easier identification. The adult has a grayish brown back contrasting with darker wings, a white throat which contrasts with a distinct brown breast-band, and grayish brown crown. The brown breast-band can extend toward the belly as a sharp spike. In their first year, the juveniles will have buff-edged or whitish upperparts and a buffy pink wash in the throat.

Adults are easily distinguished from other North American swallows. They have a more compact look, being of smaller size.  A good look at the underside shows the well-defined dark brown breast-band that is broadest at the center. The rump is completely brown, and the tail is mostly square when fully spread in flight. When held together sometimes in flight, it can look notched.

Throughout much of its western North American breeding range, the Bank Swallow nests in erodible soils on vertical or near-vertical banks and bluffs in lowland areas dominated by rivers, streams, lakes, and oceans. A highly social land bird, it nests in colonies ranging from 10 to almost 2,000 active nests. A mating pair seeks out a colony and then choses a nest site. They grasp the vertical surface and start the burrow by using their bill in a rapid, slashing motion and their feet in a scratching motion. To dislodge material from inside the burrow they eject it with vigorous kicks, wriggling their body and shuffling their wings.

Breeding locations change frequently, and they are dependent on erosion which destroys old burrows and creates new areas for fresh building. Human activities such as road building, flood and erosion control projects, and home development along waterbodies and shorelines often remove suitable breeding habitat. However, some colonies, especially on the east coast, have found abandoned gravel pits to provide good burrowing surfaces. Suitable foraging habitats surrounding a nest colony may include wetlands, open water, grasslands, riparian woodlands, agricultural areas, shrublands, and occasionally upland woodlands. Most nesting colonies are in lowland alluvial valleys and coastal areas. On the Refuge, the most likely area for Bank Swallows to nest is along the banks of Campbell Slough. The slough snakes through the wetlands in the Roth unit from Campbell Lake out to the Columbia River.

Migration in U.S. and Canada peaks early August to late September, when hundreds to thousands of Bank Swallows may be seen moving south in mixed-species flocks with Barn, Cliff, Northern Rough-winged, and Tree swallows or in loose conspecific flocks.  Many of these birds move through the central flyway and some along the Pacific Coast. So now is the time to search those swallow flocks for variety, including the smaller Bank Swallow which might have traveled down from Alaska already to enjoy what we have available to eat. They take flying or jumping insects almost exclusively on the wing. Some studies show they eat a lot of mosquitos. Let’s put out the welcome mat for these travelers!

-Susan Setterberg, Contact Station Volunteer and Birder
images sketched by Susan Setterberg