Bank Swallow (Riparia riparia)
Bank Swallows are the smallest swallow that breeds in North America. They are pale brown above, white below, and are most readily identified by the distinct brown band across the chest. Their flight is more “fluttery” than other swallows, with shallower wingbeats, and they have a notched tail. Their call is a raspy, chattering twitter. Bank Swallows feed almost exclusively on flying and jumping insects.
Bank Swallows are globally widespread, breeding across temperate parts of the Northern Hemisphere and wintering in South America and Africa.
Bank Swallows are highly colonial, nesting in groups of 10 to 2,000 pairs. Nesting burrows are excavated in vertical earthen banks, often near water. They use both natural sites, such as lake and ocean bluffs and river banks, as well as man-made sites, such as road cuts and gravel banks. Banks of sandy loamy soils are preferred over coarse, gravelly soils. Nesting burrows are approximately 60 cm long (can reach up to 90 cm long), with a nest chamber placed at the end. Larger nesting banks are generally preferred over smaller ones. Older birds and those that arrive earliest choose nesting sites higher in banks, as these are most protected from predators. Nesting activity is highly synchronized within sections of colonies. Males start excavating burrows before attracting females, and once paired, both males and females excavate the burrow, using their bills, feet, and wings. Clutch size is 2–6 eggs. The incubation period is approximately 14–15 days, and young fledge approximately 18–24 days after hatching. Both members of a pair incubate and feed young. Bank Swallows lay one clutch of eggs per breeding season, unless the first clutch fails. As with many colonial bird species, adults recognize the calls of their own offspring.
Across North America, Bank Swallow habitat has been lost to bank stabilization projects (for erosion control) and coastal development. At the same time, man-made sites (gravel pits, road cuts) have created habitat, but not enough to offset losses. Additionally, colonies in man-made sites, (e.g., gravel pits) can be destroyed if extraction activity takes place during the nesting period. Natural sites, such as banks of larger rivers and ocean bluffs, provide stable, long-term habitat, while anthropogenic sites tend to be more ephemeral. Bank Swallows are adapted to transient habitat, but within limits. One study found that about 90% of birds (both juveniles and adults) at a given colony settled within 10 km of their natal colony or previous-years' nesting bank the following year, thereby underscoring the importance of long-term natural sites. There are additional factors, beyond habitat loss, that may be contributing to population declines in several species of swallows, including Bank Swallows.
In North America, Bank Swallows have declined by over 5% per year from 1966 to 2014, resulting in a cumulative decline of 94%, according to the North American Breeding Bird Survey. The 2014 State of the Birds Report listed them as a Common Bird in Steep Decline and they are on the 2016 State of North America's Birds’ Watch List. In Canada, Bank Swallows are designated as Threatened having undergone a severe and widespread long-term decline of 98% of the population over the past 40 years. Bank Swallow is listed as a Species of Greatest Conservation Need in the Wildlife Action Plans (WAPs) for Maine, New Hampshire, Connecticut, Massachusetts, Rhode Island, New York, and Pennsylvania. They are designated as Threatened in Ontario. In California, the species has been extirpated from half its historic range as a result of bank stabilization projects. It is currently listed as Threatened there, is still vulnerable to bank stabilization and flood control projects, and continues to be in decline despite recovery efforts.
COSEWIC. 2013. COSEWIC assessment and status report on the Bank Swallow Riparia riparia in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. ix + 48 pp.
Garrison, B. A. 1999. Bank Swallow (Riparia riparia). In The Birds of North America, No. 414 (A. Poole and F. Gill, eds.). The Birds of North America, Inc., Philadelphia, PA.
H. Wright, David. (2012). 2010–2011 Bank Swallow Status Report, Sacramento and Feather Rivers.
Mead, C. J. 1979. Colony fidelity and interchange in the Sand Martin. Bird Study 26: 99–106.
North American Bird Conservation Initiative, U.S. Committee. 2014. State of the Birds 2014.
Point Blue Conservation Science Website, 2017 (http://www.pointblue.org/our-science-and-services/conservation-science/threatened-species/bank-swallow/)
Schlorff, R. W. 1997. Monitoring Bank Swallow populations on the Sacramento River: A decade of decline. Transactions of the Western Section of the Wildlife Society 33:40–48.
USGS Patuxent Wildlife Research Center. 2014. North American Breeding Bird Survey 1966–2014 Analysis.