Here at least is an unchangeable type, a visible link between Port Los Angeles and Florence on the Arno.
Communal life seems a pleasant thing to these Swallows, and there is usually a considerable stir of activity about the quarters. Dawson 1923 : 534
The Bank Swallow's scientific name - Riparia riparia - aptly describes its affinity for nesting in the streamside (riparian) banks and bluffs of rivers and streams. This species is a highly social land-bird with a Holarctic breeding distribution. It nests in colonies ranging from 10 to almost 2,000 active nests. One of only a few passerines with an almost cosmopolitan distribution, it is one of the most widely distributed swallows in the world. In the Old World, this species is known as the Sand Martin.
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. In eastern North America, however, many colonies are found in sand and gravel quarries. The size and longevity of colony sites depend greatly on erosion to maintain nesting-habitat suitability. The ephemeral nature of the nesting banks results in relatively low levels of nest-site fidelity, since there is little evolutionary benefit to maintaining long-term ties to specific colony sites.
Key studies of this species have come from North America and Europe. Hoogland and Sherman ( Hoogland and Sherman 1976 ) studied the advantages and disadvantages of Bank Swallow coloniality in Michigan; Emlen and DeMong ( Emlen and Demong 1975 ) studied breeding synchronization within colonies in New York; Persson ( Persson 1987c , Persson 1987a , Persson 1987b ) looked at age structure, sex ratios, and survival rates of populations in Sweden; Szep ( Szep 1993 , Szep 1995a ) explored how breeding populations in Hungary are affected by levels of rainfall on their African wintering grounds; Beecher et al. ( Beecher et al. 1981b , Beecher et al. 1981a ) looked at parental recognition of nestling voices in colonies; Beecher and Beecher ( Beecher and Beecher 1979 ) and Kuhnen ( Kuhnen 1985 ) studied how burrow-digging by nesting pairs helps establish and solidify the pair bond, although extra-pair breeding is common; and Jones ( Jones 1986a ) researched how male Bank Swallows distinguish heavier, apparently receptive, females in flight and preferentially chase them for breeding.
Colonies at sand and gravel quarries are easily studied because of their accessibility, and countless banding studies have been conducted on this species, producing considerable information on the breeding-population dynamics and colony-site fidelity of Bank Swallows. Relatively little information exists, however, on postbreeding dispersal, migration, and wintering ecology.