Swifts — Family Apodidae
Black Swift Cypseloides niger
Nesting only around waterfalls and sea cliffs, the Black Swift is one of southern California’s rarest breeding birds. Only six sites are known (Foerster and Collins 1990), none in San Diego County. Here the Black Swift occurs as a rare migrant, mainly in spring, flocking with other swifts and swallows.
Migration: Only a few Black Swifts are found in San Diego County each year, and some years pass with none at all. The atlas period from 1997 to 2001 was typical with zero to six noted each year and no more than three per day. There are three records, however, of large flocks, of 300 at Carlsbad (probably Buena Vista Lagoon) 29 May 1948 (AFN 2:189, 1948), up to 40 at Buena Vista Lagoon (H5/H6) 21–24 May 1980 (AB 34:816, 1980), and up to 200 at Point Loma (S7) 27–28 May 1987 (M. Rosenquist, R. E. Webster, AB 41:488, 1987). Records of the Black Swift are concentrated in two regions of San Diego County: a narrow strip along the coast and Palomar Mountain. The concentration along the coast is due to the overcast that commonly blankets the coast in spring and keeps the swifts flying low, as well as to the coastal lagoons (two at Buena Vista Lagoon, H6, 23 May 1999, L. E. Taylor). Black Swifts, like other swifts and swallows, are drawn to forage over water. The accumulation of records from the Palomar Observatory (D15) is due to Roger Higson’s observations there from 1980 to 1985. But Black Swifts may also be attracted to mountain tops, as suggested by three at the summit of Hot Springs Mountain (E20) 8 June 2001 (K. L. Weaver).
In spring, the Black Swift occurs principally in May. The only April records are of two along the Santa Margarita River at De Luz Road (C7) 24 April 1999 (K. L. Weaver) and one along Miramar Road 0.5 mile east of Interstate 805 (O8) 30 April 1999 (W. E. Haas). The only records for June are that for Hot Springs Mountain and the only specimen for San Diego County, found dead under a telephone wire 4 miles north of Escondido 5 June 1921 (MVZ 41912; Dixon 1921).
The Black Swift is even less frequent in San Diego County in fall than in spring. From 1997 to 2001 there were seven records in spring, only one in fall. Of at least 16 fall records total, all are from Palomar Mountain or Point Loma except for two at Lake Henshaw 7 October 1984 (R. Higson, AB 39:103, 1985) and one at Escondido 24 October 1963 (AFN 18:74, 1964). Fall records extend from 23 August (1985, one at Point Loma, R. E. Webster, AB 40:159, 1986) to 24 October (1963, at Escondido, and 1983, two at Palomar Mountain, R. Higson, AB 38:247, 1984). The largest flock yet noted in fall was of 12 at Palomar Mountain 14 October 1981 (R. Higson, AB 36:218, 1982).
Chimney Swift Chaetura pelagica
The Chimney Swift breeds largely in the eastern half of the United States. Since the 1980s, however, small numbers have been showing up regularly at a few spots in California, especially Los Angeles, where the birds are suspected to breed. The Chimney Swift is now known to be more likely in southern California in midsummer than Vaux’s Swift. Nevertheless, this range expansion has hardly touched San Diego County, where there are only 11 records.
Migration: San Diego County’s Chimney Swifts have all been near the coast, on dates ranging from 21 May to 22 August—thus overlapping minimally with the migration of Vaux’s Swift. Records more recent than the four listed by Unitt (1984) are of six to eight in downtown San Diego (S9) 11 July 1982 (E. Copper, AB 36:1017, 1982), one near Del Mar (M7) 7–12 June 1983 (D. Delaney, AB 37:913, 1983), two at the northeast corner of Balboa Park (R10) 16 June 1989 (P. Unitt, AB 43:1368, 1989), three near Santee (P12) 22 June 1990 (R. E. Webster, AB 44:1188, 1990), three at Chula Vista (U10) 21 July 1990 (E. Copper, AB 44:1188, 1990), two at San Elijo Lagoon (L7) 21 May 1991 (R. E. Webster, AB 45:496, 1991), and two in Mission Valley 6.5 miles inland (R9) 29–30 June 1994 (P. Unitt, NASFN 48:989, 1994). The only specimen is still the one from San Elijo Lagoon 12 July 1968 (Devillers 1970b, SDNHM 36690).
Vaux’s Swift Chaetura vauxi
California’s smallest swift is largely a migrant through San Diego County, occasionally common. It winters regularly, though, around Oceanside, the only area where Vaux’s winters regularly north of central Mexico. Migrating flocks sometimes roost in large numbers in chimneys and other man-made structures, where they are at risk of being burned or cooked, as well as of blundering into living rooms. Concentrated roosts represent a bottleneck of vulnerability for a species already of conservation concern because of its reliance for breeding on old-growth forests in the Pacific Northwest.
Migration: In spring, Vaux’s Swifts are seen mainly in the coastal lowland and Anza–Borrego Desert, with very few observations between; the birds evidently fly over San Diego County’s mountains quickly. During the atlas period, our high counts were of 160 at Torrey Pines State Reserve (N7) 1 May 1999 (K. Estey), 150 near Dehesa (Q15) 22 April 1999 (A. Young), and 145 near the east end of Agua Hedionda Lagoon 4 May 1996 (W. E. Haas). These figures were eclipsed in 2002 with the discovery of a roost in an old brick chimney at 8th Avenue and Broadway in downtown San Diego (S9). From 4 to 7 May at least 1000 individuals were around downtown San Diego, many entering this chimney (K. B. Clark). In 2003 several hundred used the roost at least from 25 April to 6 May (M. Sadowski). Vaux’s Swifts are much less common in the desert than along the coast; maximum counts are of 30 in Vallecito Valley (M24) 6 May 1998 (R. Thériault) and 50 at the Ram’s Hill sewage ponds (H25) 8 May 1994 (P. D. Jorgensen).
The species’ spring migration peaks in the last week of April and first week of May. From 1997 to 2001, first spring dates ranged from 5 to 11 April and last spring dates ranged from 1 May (1997) and 10 May to 26 May, except for one in lower Los Peñasquitos Canyon (N8) 6 June 1999 (M. Baumgartel). Extreme dates in previous years are 4 April (1981, San Diego, AB 35:862, 1981) and 2 June (1984, Point Loma, S7, D. M. Parker, AB 38:961, 1984).
In fall, Vaux’s Swift is generally seen in numbers smaller than in spring, though the difference may be due to the difference in weather at the two seasons. In cloudy or stormy weather the birds fly low and are more conspicuous than in clear weather that commonly prevails uninterrupted through September and October. In fall 2002, Vaux’s Swifts roosted in the same chimney at 8th and Broadway as in the spring; they were seen 4 September–21 October, practically the same interval defined by all previous fall records combined, with a daily maximum of 70 individuals (M. Sadowski).
Winter: The subspecies of Vaux’s Swift breeding in western North America winters primarily in southern Mexico and Central America, being only casual at this season over most of California. Yet it is annual in winter in San Diego County, in the valleys of the lower Santa Margarita and San Luis Rey rivers. It has been recorded on 15 of 34 Oceanside Christmas bird counts, 1968–2001, with a maximum of 208 on 22 December 1979. From 1997 to 2002 we found it at Whelan Lake (G6), Windmill Lake (G6), or O’Neill Lake (E6) every winter, with as few as four in 1999–2000 but up to 40 at Whelan Lake 14 December 2000 (P. A. Ginsburg) and 15 at Windmill Lake 23 December 2000 (P. Unitt). Away from this center Vaux’s Swift is far less frequent, recorded on only two Rancho Santa Fe Christmas bird counts, 1981–2001 (one or two individuals), and two San Diego counts, 1953–2001 (maximum 10 on 15 December 1990). Other winter records in the coastal lowland are from near San Onofre (C1; one on 7 February 1996, L. R. Hays, NASFN 50:224, 1996; at least 100 on 24 February 1999, D. W. Aguillard, NAB 53:209, 1999), Batiquitos Lagoon (J6/J7; one on 21 December 1987, D. R. Willick, AB 42:321, 1988), Escondido (one on 22 January 1980, AB 34:307, 1980), the east end of Lake Hodges (K11; one on 14 December 1997, B. K. Schram, FN 52:258, 1998), San Elijo Lagoon (L7; one on 6 and 22 March 1964, AFN 18:388, 1964), Old Mission Dam (P11; five on 15 January 1980, AB 34:307, 1980), Santee Lakes (P12; nine on 15 January 2001, E. Wallace), Point Loma (S7; one on 6 January 2001, J. C. Worley), Sweetwater Reservoir (S12; 50 on 16 and 17 January 2001, G. Chaniot, NAB 56:224, 2002), and the Tijuana River valley (one on 8 December 1990, G. McCaskie, AB 45:321, 1991). Most unexpected were two small flocks on the east side of the mountains in 2000–01, of about 20 near Vallecito Stage Station (M25) 2 December 2000 (P. K. Nelson) and six at Tule Lake (T27) 16 February 2001 (F. L. Unmack).
Conservation: The northern subspecies of Vaux’s Swift has suffered population declines as a result of logging of its breeding range, where it depends on large old trees and holes excavated by Pileated Woodpeckers (Bull and Cooper 1991, Bull and Hohmann 1993, Sterling and Paton 1996). The California Department of Fish and Game considers Vaux’s Swift a species of special concern. Of relevance in southern California is migrants’ concentrating in communal roosts in artificial structures, where large numbers may be trapped or killed. Originally hollow trees served as roosts, but now buildings attract the swifts’ attention. A flock at Point Loma died when it attempted to roost in a boiler for heating a building (M. F. Platter-Rieger). Sometimes, especially in stormy or drizzly weather, flocks of Vaux’s Swifts attempting to roost in chimneys come down into houses, bringing bedlam to the terrorized residents and death to most of the swifts (e.g., Huey 1960). Large roosts may contain a significant fraction of the entire population; one in downtown Los Angeles is used by up to 10,000 birds (K. L. Garrett, K. C. Molina).
Taxonomy: Only the pale nominate subspecies of Vaux’s Swift, C. v. vauxi (Townsend 1839), is known from California.
White-throated Swift Aeronautes saxatalis
Cruising the skies by day for flying insects, the White-throated Swift touches ground only where it can cling to vertical surfaces. Cliffs, sea bluffs, and desert badlands offer the swift crevices for both roosting and nesting. In addition to these traditional habitats, the White-throated Swift now also takes advantage of crevices and holes in buildings and bridges. The White-throated is the only swift that breeds in San Diego County; it is locally common year round.
Breeding distribution: The White-throated Swift occurs widely through San Diego County during the breeding season, but actual nesting is constrained by the need for suitable sites. The distance the birds range from nest sites to forage is not known but probably is at least 10 miles (Ryan and Collins 2000). In the Anza–Borrego Desert White-throated Swifts inhabit the badlands, where deep crevices have been eroded into steep banks. The Carrizo Badlands constitute the single largest block of atlas squares in which we confirmed White-throated Swift nesting, and counts here range up to 30 near Palm Spring (N27) 24–27 April 1998 (D. C. Seals). In San Diego County’s rugged mountains there are many cliffs and boulder outcrops offering nest sites. Undoubtedly we missed many of these sites because of difficult access, but the birds take advantage of them throughout the county, nearly to the summit of Cuyamaca Peak (M20; four on 14 July 2001, entering crevices in the west-facing cliffs just below the summit, J. R. Barth). Along the coast, sea cliffs, especially the bluffs between La Jolla and Los Peñasquitos Lagoon, provide another major habitat for the White-throated Swift,. This was our most regular site for large numbers of swifts, up to 106 in Torrey Pines State Reserve (N7) 4 March 2000 (K. Estey).
Nesting: Hidden in crevices in cliffs, White-throated Swift nests are almost impossible for a person standing safely on the ground to see. Atlas observers had to rely on seeing the swifts entering crevices repeatedly and hearing the young calling from within them to identify nest sites. The White-throated Swift has also taken to nesting in man-made structures; the artificial sites we noted most frequently were the drain holes under box-frame bridges, the same sites so favored by the Northern Rough-winged Swallow. Other nests are in crevices in tall buildings, such as expansion joints in the hospital in Camp Pendleton (E6; P. A. Ginsburg).
White-throated Swifts appear to begin nesting appreciably earlier in the Anza–Borrego Desert than on the coastal slope. Several reports of nests in April, and one of a nest with nestlings in Cañon sin Nombre (P29) 29 March 1999 (D. C. Seals), suggest the birds begin laying in this area in the first week of March. Desert nesting may extend into summer, as well, with a nest with nestlings in Sandstone Canyon (M27) 21 June 2001 (R. Thériault) and occupied nests about 2200 feet elevation in Borrego Palm Canyon (F23) 2–5 July 1999 (L. J. Hargrove). On the coastal slope our earliest nests were in the Interstate 805 bridge over the Sweetwater River (T11) 18 April 1999 (W. E. Haas), latest (with nestlings) in a bridge over the San Luis Rey River, Oceanside (G5), 16 July 2000 (R. E. Fischer).
Winter: The White-throated Swift is migratory over much of its range, but in San Diego County there is no clear variation in its abundance by season. It is seen at many of the same sites year round. Winter estimates during the atlas period range up to 300 at Sweetwater Reservoir 16 December 2000 (P. Famolaro). Weather conditions affect its visibility greatly: swifts are best seen on overcast days, when they must forage below the clouds. On warm clear days the birds may forage so high they are out of sight; when the weather is cold or stormy they remain in their roosts all day, revealing themselves only with occasional calls. They may also go torpid (Bartholomew et al. 1957).
The White-throated Swift is seen far less frequently in the mountains in winter than in summer, but we still noted the species three times in the Cuyamaca and Laguna mountains above 4000 feet elevation, with up to 20 at 5100–5600 feet elevation along upper La Posta Creek (P24) 19 December 2001 (E. C. Hall, J. O. Zimmer). The swift appears to be regular through the winter at elevations up to 5800 feet in the Santa Rosa Mountains (C27), with up to 15 on 21 January 2000 (P. Unitt).
Conservation: No trends in the abundance of the White-throated Swift in San Diego County are clear. Variation in numbers seen on systematic counts due to variation in weather is enormous, overwhelming variation due to other sources. Man-made structures, especially freeway bridges, have given the species many new nesting sites. Some natural sites have been converted to rock quarries, but the swift has recolonized some abandoned quarries. Urbanization is likely bad for the swift’s food supply, however, extensively paved areas generating fewer aerial insects than natural habitats.
Taxonomy: According to Behle (1973), all White-throated Swifts in the western United States and northern Mexico constitute one subspecies, the nominate A. s. saxatalis (Woodhouse, 1853).