Cuckoos — Family Cuculidae
Yellow-billed Cuckoo Coccyzus americanus
In western North America, the Yellow-billed Cuckoo lives only in extensive stands of mature riparian woodland. On a statewide basis, the cuckoo is now the bird closest to extirpation from California, reflecting the decimation of its habitat. The California Department of Fish and Game has listed it as endangered. In San Diego County the Yellow-billed Cuckoo is now only a rare and sporadic summer visitor, not known to have nested for decades.
Breeding distribution: Since 1980, the Yellow-billed Cuckoo has been encountered in San Diego County nine times, always in or near significant stands of riparian willows and cottonwoods. Along the Santa Margarita River, at the upper end of Ysidora Basin (F5), there was one 4–5 July 1984 (L. Salata, AB 38:1062, 1984) and another 7–11 July 2000 (D. Kisner, J. M. Wells). One was at Guajome Lake (G7) 11–12 June 1992 (F. R. Tainter, AB 46:1179, 1992). At the uppermost end of the basin of Lake Hodges (K11), up to three individuals were seen 14–22 July 1992 (J. Smith, AB 46:1179, 1992) and a single bird was seen 1–4 June 1997 (E. C. Hall, FN 51:1054, 1997). In the Tijuana River valley one was seen 18 August 1985 (J. Oldenettel, AB 40:159, 1986) and another, in Smuggler’s Gulch (W10), 28 June 2001 (P. Howard, NAB 55:483, 2001). On the desert slope of the mountains, along San Felipe Creek 1 mile west-northwest of Scissors Crossing (J22), one was seen and heard 6–12 July 2001 (T. Gallion, P. D. Jorgensen, NAB 55:483, 2001) and again 12 July 2002 (P. D. Jorgensen, NAB 56:486, 2002)
Nesting: Using primarily willow twigs in southern California, the Yellow-billed Cuckoo builds a rather coarse nest, placing it in the outer branches of willow trees (Jay 1911, which see for photos of nests). The only dates of nesting reported from San Diego County are of a female with a brood patch collected at Escondido 30 June 1915 (Dixon 1916) and egg sets collected at Escondido 2 July 1932 and 3 July 1915 (Willett 1933).
Migration: Of all summer visitors to California, the Yellow-billed Cuckoo is the latest to arrive, seldom seen before the first of June. Before the population collapse, the cuckoos sometimes occurred earlier; at Pauma Valley (E12) E. Beemer noted one 4 May 1948, and in Los Angeles County Jay (1911) reported seeing one 5 May 1907 and finding newly hatched young 10 May 1901. But otherwise dates for the cuckoo in San Diego County range only from 1 June to 23 August (1969, one at Batiquitos Lagoon, J7, AFN 24:100a, 1970). There are only three or four records of migrants away from riparian woodland.
Conservation: The Yellow-billed Cuckoo was never common in San Diego County but confirmed nesting at Escondido in 1915 and 1932 and at Bonita in 1932 (Dixon 1916, Willett 1933). Before 1980 it was reported also from possible breeding habitat at Pauma Valley, the San Luis Rey River near Bonsall (E. Beemer), 3 miles north of Vista (C. S. Wilson, AB 32:1209, 1978), Poway (Belding 1890), Sorrento Valley (Sams and Stott 1959), and the Tijuana River valley (von Bloeker 1931).
The collapse of Yellow-billed Cuckoo’s population throughout the western United States was due primarily to the wholesale destruction of riparian woodland, which now covers only a few percent of its original extent. Spraying of pesticides in the 1950s is likely responsible for decimating the cuckoos in the remaining tracts of their habitat in coastal southern California (Gaines and Laymon 1984). Along the Colorado River, a possible source population for repopulation of coastal southern California has been nearly eliminated. Most of the once vast forest of native willows and cottonwoods there was chopped down and bulldozed, then replaced with the exotic tamarisk, a process greatly accelerated by floods in the mid 1980s (Laymon and Halterman 1987, Rosenberg et al. 1991). Factors operating over a regional scale are driving the cuckoo to extirpation; it has declined even where habitat is stable or increasing. The cuckoo requires the largest stands of riparian woodland of any of California’s riparian birds; in the Sacramento Valley, Gaines (1974) reported it absent from tracts covering less than 3 hectares, and far larger tracts may be necessary to sustain a viable population.
Taxonomy: The Yellow-billed Cuckoos of western North America are significantly larger than those of the East, but there appears to be too much overlap in measurements for the populations to be recognized as subspecies (Patten et al. 2003). In any case, the taxonomic question does not vitiate the urgency of conservation measures to save the Yellow-billed Cuckoo over a huge fraction of its natural range.
Greater Roadrunner Geococcyx californianus
An emblem of the deserts of America’s Southwest, the Greater Roadrunner is an uncommon resident of San Diego County’s Anza–Borrego Desert. It also occurs in sage scrub and open chaparral on the coastal slope but is retreating in the face of urban sprawl. As a large bird requiring a large territory, with a low capability for dispersal, the roadrunner copes poorly with habitat loss and fragmentation. It is disappearing rapidly from canyons surrounded by developed areas.
Breeding distribution: Roadrunners range through most of San Diego County in low density. On the coastal slope, they are most numerous in sage scrub with little development or scattered rural homes and agriculture only. Some higher counts are of four, including three calling males, in Las Pulgas Canyon (E4) 26 May 2001 (P. A. Ginsburg), five, all singing males, southeast of Fallbrook (D9) 19 May 1999 (E. C. Hall), and five in the eastern undeveloped part of the Wild Animal Park (J13) 3 June 1999 (D. and D. Bylin). The roadrunner also occurs in broken chaparral up to about 4000 feet elevation (pair in Scove Canyon, P22, 18 June 1997, P. Unitt).
In the better-vegetated parts of the Anza–Borrego Desert the roadrunner’s numbers are similar to those in coastal sage scrub (up to five calling males in the Box Canyon area, L23, 26 April 1999, R. Lantz). In the badlands and sparsely vegetated sandy areas near the Imperial County line the roadrunner is scarce—in 10 atlas squares we noted used nests or tracks in the sand but never saw the birds themselves. In some areas, such as the Santa Rosa Mountains, Borrego Mountain, Ocotillo Badlands, and Split Mountain, our not finding even these traces may reflect the roadrunner’s absence.
Nesting: The roadrunner’s nest is a shallow dish about one foot across, built of coarse sticks. In the Anza–Borrego Desert the nests are built in various trees or shrubs; observers reported ocotillo, mesquite, palo verde, desert apricot, and the skirt of a fan palm as sites. On the coastal slope thickets of prickly pear, where we noted three nests, may be preferred for their ability to deter predators. But we also noted nests in some nonnative plants: tamarisk, Peruvian pepper, and eucalyptus.
In the wet spring of 1998 we noted nest building by roadrunners as early as 9 February and adults carrying food items as early as 20 March (near the Borrego Air Ranch, H26, M. L. Gabel). Sharp (1907) collected roadrunner eggs at Escondido as early as 14 February, and K. L. Weaver found a nest with three eggs near Lake Hodges as early as 13 February in 1982. But both egg collections and our observations from 1997 to 2001 point to March through early June being the season for the roadrunner’s egg laying in dry to average years.
Winter: Mated pairs of adult roadrunners maintain their territories year round, and the degree to which the young disperse is unknown (Hughes 1996). The winter distribution we observed did not differ appreciably from the breeding distribution, though we noted roadrunners twice in winter at elevations higher than we found them in the breeding season, with one about 4000 feet near Julian (K20) 1 December 1997 (E. C. Hall) and one at 4700 feet at Stonewall Mine (M20) 4 January 2000 (S. Jorgensen). Our highest winter count in a single atlas square was of nine in south Borrego Springs (G24) 19 December 1999 (P. D. Ache et al.).
Conservation: The roadrunner adapts to low-intensity rural development that leaves much open ground. It appears to be more numerous in the town of Borrego Springs than in the surrounding undisturbed desert. But the style of urban development characteristic of coastal southern California, where the ground surface is covered completely with buildings, landscaping, and pavement, eliminates the roadrunner. The roadrunner’s very name harks back to the days of the horse and buggy, when the birds could be seen commonly along San Diego’s unpaved streets (Belding 1890, Stephens 1919a). Today, speeding traffic kills roadrunners regularly. The species’ decline in metropolitan San Diego is evident from results of San Diego Christmas bird counts: from 1963 to 1972 the count’s average was 8.2 roadrunners; from 1997 to 2001 it was only 1.8. At San Elijo Lagoon (L7) the roadrunner was in decline from 1973 to 1983 (King et al. 1987) and extirpated by 1997.
Soulé et al. (1988) and Crooks et al. (2001) identified the roadrunner as the most sensitive to habitat fragmentation among the eight scrub species they addressed. On the basis of surveys in 1997, Crooks et al. (2001) reported the roadrunner from only one (Sandmark Canyon, Q9) of 34 canyons isolated by urbanization in metropolitan San Diego. They projected that the roadrunner has a 95% possibility of persisting for 100 years only in fragments of 157 hectares or larger. Even this, however, likely underestimates the roadrunner’s sensitivity. Atlas observers did not report the species from any long-isolated canyon, only from recently isolated ones like Rice Canyon, Chula Vista (U11; most recent report, juvenile 24 July 2000, T. W. Dorman). The long-isolated native scrub of Point Loma (S7) and Tecolote Canyon (Q8/Q9) has been covered exhaustively, so the roadrunner’s extirpation from those sites is certain—and suggests that isolated habitat of even 400 hectares is insufficient to sustain the birds indefinitely.