The Bank Swallow (Riparia riparia) breeds in colonies across much of the Northern Hemisphere, though its nesting requirements limit it to specific habitats. Our local populations have wintered in South America and will soon be winging back to Connecticut to raise their young.
The Bank Swallow is the smallest of the swallows found in the United States. Like other swallow species it has long, pointed wings and a swift, swooping flight pattern. Its pale gray-brown back contrasts sharply with its clean white breast and belly and a dark band across its breast helps to differentiate it from the tree swallow. Check out the tails of passing swallows when making an identification – the Barn Swallow has a deeply forked tail, the Tree Swallow’s tail is squared and the Bank Swallow is somewhere in between, with a notched tail.
Bank Swallows can be found in rural areas that offer sandbanks for nest sites. Riverbanks provide the ideal habitat, but human construction sites where bare sand is exposed (such as sand pits and mounded excavated sand) also provide these birds with the appropriate materials for nest building.
They nest in colonies, with each pair of adults excavating their own horizontal tunnel two to three feet deep into the sandbank. A nest of grass and rootlets is built at the end of the tunnel. Like many other swallow species, the Bank Swallows will line their nest with the white feathers of other birds, such as domesticated ducks. Both male and female will build the nest, incubate the eggs and feed the young. Pairs within the colony time their breeding to be synchronous with the others in the colony; their young will hatch, grow and fledge together.
Bank Swallows feed over meadows and water where insects tend to swarm. They can be seen feeding as a group, catching insects in flight. A swallow’s tiny bill belies the size of its mouth, which opens wide to scoop up its aerial prey. It will also drink on the wing, gliding low over water to dip its bill for a sip. If you see one splash about briefly at the water’s surface, you have just witnessed a swallow bathing.
If you have discovered a Bank Swallow colony like the one pictured here, it will likely not be there in the future. Riverbanks erode and human construction sites are altered over time. Bank Swallows returning from their wintering grounds will need to seek out a new nest site if their previous site has been destroyed.
In Europe the Bank Swallow is known as the Sand Martin. In the United Kingdom artificial nest sites are constructed for these colonial nesting birds
[Audubon’s Climate Report lists Bank Swallows as Climate Endangered.]