The Cliff Swallow’s breeding range extends from w. and central Alaska, n. Yukon, n. Mackenzie, central Keewatin, n. Manitoba, n. Ontario, s. Quebec (including Anticosti I.), New Brunswick, Prince Edward I., and Novembera Scotia south to s. Alaska, n. Baja California (Godfrey 1986, Phillips 1986, Am. Ornithol. Union 1998), the Pacific slope of Mexico south to Sinaloa and along the Mexican plateau south to central Oaxaca (Howell and Webb 1995) and s. Texas, and east to the Atlantic and Gulf coasts of the U.S. Colonies have been found on the north side of the Brooks Range, with some within ~30 km of the Arctic Ocean, in ne. Alaska (Sage 1973, P. Goldman pers. comm.). Less common breeder in the Gulf states and the e.-central and ne. U.S., but the species is increasing in most of these areas, especially the Gulf states and the Ohio Valley.
Since at least 1980, there have been scattered reports of nesting activity on the winter range, primarily in Buenos Aires Province, Argentina (Petracci and Delhey 2004). Nests have been built, but no known cases of egg laying have been documented to date.
The winter range extends apparently from s. Brazil (São Paulo province) and possibly se. Paraguay south to s.-central Argentina. Distribution within this region is poorly known, although most birds apparently winter in lowlands along the Rio Paraná and Rio Uruguay north and northwest of Buenos Aires (Buenos Aires, Entre Rios, and Corrientes provinces of Argentina, and w. Uruguay; Olrog 1967, P. Burke pers. comm., A. Jaramillo pers. comm., V. Bowers pers. comm.). Wintering birds have also been recorded west to Tucumán province, Argentina. South of Buenos Aires, birds occasionally occur in large numbers but are more irregular than farther north (A. Jaramillo pers. comm.). Recorded several times as far south as Tierra del Fuego and occasionally in the Falkland I. Rare in Chile and the high Andes. The subspecies P. p. pyrrhonota winters in ne. Argentina, P. p. melanogaster in nw. Argentina; the wintering ranges for P. p. ganieri, P. p. tachina, and P. p. hypopolia are unknown (Fjeldså and Krabbe 1990). Small numbers are reported to winter occasionally with flocks of Barn Swallows in the Pacific slope lowlands of Panama (Ridgely 1976). Casual in Barbados, St. Kitts, Guadeloupe, St. Lucia, and Dominica, mostly in winter but a few records in spring and fall (Bond 1971, Am. Ornithol. Union 1998, Feldmann et al. 1999). Stragglers have been reported in December in the Imperial Valley of California (Grinnell and Miller 1944), along the Lower Colorado River in Arizona (Phillips et al. 1964), and on the Pacific Coast (north to Vancouver) and the Gulf Coast on Christmas Bird Counts. Report of Cliff Swallows being “common” in the Salton Sea region in winter (van Rossem 1911) is likely erroneous.
Accidental on Wrangel I., Siberia, and s. Greenland (Am. Ornithol. Union 1998). At least 6 records for the British Isles (Rogers 1997, 1998).
This species’ breeding range has been influenced heavily during the last 100–150 years by widespread construction of bridges, buildings, and culverts, which provide nesting sites in areas formerly uninhabited, and by the introduction of House Sparrows (Passer domesticus) which usurp nests. In the ne. U.S., where Cliff Swallows were probably never common, this swallow began to increase in the early to mid-1800s as land was cleared and more buildings constructed (Bent 1942). With the introduction of the House Sparrow in the late 1800s, and its usurpation of swallow nests, Cliff Swallow numbers began to decline in the ne. U.S. and remain low today (Forbush 1929, Silver 1993, 1995).
In the se. U.S., the breeding range has expanded south and east during the last 50-75 years with new colonies found each year. A major eastward range expansion has occurred in Tennessee since the 1930s (Alsop 1981). Breeding began in Alabama in 1951 (Imhof 1976), Georgia in 1965 (Dopson and Peake 1967), Florida in 1975 (Sykes 1979, Lewis and McNair 1998), the Carolina piedmont in 1965 (McConnell 1981) with a major expansion in the 1980’s (McNair 2013), and Louisiana in 1980 (Viers 1991). Breeders reached the Mississippi coast by 1986 (Spence and Toups 1986).
The breeding range has also expanded elsewhere east of the Great Plains. Breeders have increased since the mid-1970s in the coastal plain of Maryland (Patterson 1981) and Virginia (Watts et al. 1996), since the early 1980s in W. Virginia (Igou 1986), and since the late 1980s in s. Illinois (Robinson 1989). Breeding was detected in Delaware in 1993 (Ednie 1994). The species is now breeding in larger numbers in the eastern Great Plains (e.g., in e. Oklahoma, e. Kansas, e. Nebraska) than 50 years ago (CRB, MBB) and has expanded into s. Arkansas (Tumlison 2009). Only in the ne. U.S. does nest usurpation by House Sparrows (or forest cover) appear to be limiting breeding-range expansion.