Cliff Swallow (Petrochelidon pyrrhonota)
Cliff Swallows are characterized by iridescent blue-brown upperparts, a cream colored breast, and chestnut around the throat. Distinctive markings are a white forehead, rusty rump patch and square tail. The breeding call is a guttural, squeaky rasp. They also use a softer “chur,” contact call and louder “kee-er” alarm call. They feed on swarming insects that rise on thermals, and tend to forage at a higher altitude than other North American swallows.
They breed across much of North America and winter in South America, specifically in parts of Argentina, Brazil, and Paraguay.
Cliff Swallows originally nested on natural sites, such as rock cliffs and bluffs, and historically probably were uncommon in the Northeast. After European settlement, however, their range expanded as they took advantage of man-made structures for nesting sites. In California, Pacific Northwest, and the Northeast, Cliff Swallows primarily use buildings for nesting. Buildings are not commonly used in the Midwest or Southeast, where, instead, natural cliff faces, bridges, and culverts are used. In the Northeast they are often found in agricultural areas, which provide open areas for foraging, a mud source, and structures upon which to build nests. A source of mud for nest building is a critical habitat feature. Cliff Swallows are extremely colonial, and larger colonies can reach up to thousands of pairs, with nesting activity highly synchronized within larger colonies. Compared to western colonies, those in the Northeast are smaller, rarely exceeding 100 pairs. Cliff Swallows construct bottle-shaped mud nests attached to a vertical surface. In the Northeast, nests are most often constructed under the eaves of buildings. Old nests are readily re-used. Nests are constructed one pellet of mud at a time, which is carried in the beak from a nearby mud source. Clutch size is 1–6 eggs, (usually 3–4). The incubation period is approximately 14 days, and young fledge approximately 21–23 days after hatching. Both members of a pair incubate and feed young. Cliff Swallows have one brood per breeding season, unless the first clutch fails. Adults recognize the calls of their own offspring.
Cliff Swallow numbers probably reached their peak in the Northeast around 1840–1860 and gradually began to decline in about 1880. Factors contributing to the decline include the decline of agriculture, regrowth of forests, suburbanization, and competition from introduced House Sparrows (Passer domesticus), which aggressively usurp nests (Silver 1993, 1995). In the mid-1980s, the Cliff Swallow decline became dramatic in the Northeast. There are additional factors, beyond habitat loss, that may be contributing to population declines in several species of swallows, including Cliff Swallows.
Cliff Swallow is designated as a Species of Greatest Conservation Need in the 2015 Wildlife Action Plans (WAPs) for Maine, New Hampshire, Connecticut, Massachusetts, and are designated as Threatened in New Hampshire and Special Concern in New Jersey. They no longer breed in Rhode Island. Cliff Swallows have declined in Massachusetts by about 48% since 1985 and by about 27% since 2000. Massachusetts Breeding Bird Atlas 2 found that the combined threat of habitat loss and competition from invasive birds has reduced the already-small population to less than a third of its Atlas 1 size. In 2015, a Massachusetts survey found approximately 32 colonies in the state, with most of these made up of less than 5 pairs. By 2020, fewer than 15 colonies were detected in the state. Of 12 colonies
inventoried in 2020, the 2 largest colonies, one with 99 active nests and another with 38 active nests accounted for approximately 50% of the known Cliff Swallows nesting in Massachusetts. These trends are similar throughout the northeastern United States. Although declining in the Northeast, Pacific Northwest, Coastal California, and Great Lakes, the Cliff Swallow breeding range has been expanding in the South and East and parts of the Great Plains. Cliff Swallow is not on the 2016 State of North America’s Birds’ Watch List.
Breeding Bird Atlas Explorer (online resource). 2017. U. S. Geological Survey Patuxent Wildlife Research Center. http://www.pwrc.usgs.gov/bba. Data compiled from: Massachusetts Breeding Bird Atlas 2007–2011.
Brown, Charles R., Mary B. Brown, Peter Pyle and Michael A. Patten.(2017). Cliff Swallow (Petrochelidon pyrrhonota), The Birds of North America (P. G. Rodewald, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America: https://birdsna.org/Species-Account/bna/species/cliswa
Emlen, Jr., J. T. 1952. Social behavior in nesting Cliff Swallows. Condor 54: 177–199.
Partners in Flight. 2012. Species assessment database.
Sauer, J. R., J. E. Hines, J. E. Fallon, K.L. Pardieck, D.J. Ziolkowski, Jr., and W.A. Link. 2016. The North American Breeding Bird Survey, Results and Analysis 1966–2015, Version 01.30.2015. USGS Patuxent Wildlife Research Center, Laurel, MD.
Silver, M. 1993. Second-year management of a Cliff Swallow colony in Massachusetts. Bird Observer 21: 150–155.
Silver, M. 1995. Conservation of Cliff Swallows in Massachusetts. Bird Observer 23: 327–332.