Pigeons and Doves — Family Columbidae
Domestic Pigeon, Rock Dove, or Rock Pigeon Columba livia
Native to rocky cliffs in the Old World, the Rock Dove has been domesticated for millennia. Domestic Pigeons were brought to North America by the earliest French and English settlers (Schorger 1952) and spread in tandem with western civilization. Historical data on their establishment in southern California are practically nonexistent, but the pigeons have been abundant here for decades. In San Diego County they nest on buildings almost exclusively; in natural habitats only occasional wanderers are seen flying overhead.
Breeding distribution: The Domestic Pigeon is common in heavily urbanized areas. Our counts for this atlas do not represent its true abundance, as even in cities observers focused their time far more on parks and remnant native habitats than around the buildings where pigeons congregate. In the breeding season our highest count was at Encinitas (K6), where the birds use supports for the railroad bridge (154 on 22 April 2001, J. Ciarletta). In San Diego’s back country Domestic Pigeons are common around farm buildings in some places (up to 55 in Ballena Valley, K17, O. Carter), absent in others. In the higher mountains they are rare but nest possibly at Julian (J20; up to three on 26 June 2001, O. Carter) and definitely near Mount Laguna (P23; pair building a nest 5 July 2000, E. C. Hall). In the Anza–Borrego Desert, Domestic Pigeons are resident in small numbers in the communities of Borrego Springs (up to 20 in square F25 on 31 March 1998 and 28 April 1999, P. D. Ache) and Ocotillo Wells (up to three, plus a nest with eggs, in square I29 on 8 May 2001, J. R. Barth). A single bird was in the community of Canebrake (N27) 29 April 2000 (R. and S. L. Breisch).
Nesting: In San Diego County the Domestic Pigeon nests on buildings and bridges almost exclusively. The only other nest site atlas observers described was inside a railroad tunnel, where R. Breisch and J. Determan found an abandoned egg 2 December 2001. Most nesting in San Diego County appears to take place from March to July, though this season may represent more the season when atlas observers were looking for it. Some nesting takes place almost if not completely year round, as attested by adults feeding fledglings in Santee (P12) 14 February 1998 (C. G. Edwards) and in an underground parking garage in the Hillcrest area of San Diego (R9) 12 November 2001 (P. Unitt), meaning egg laying in late December and late September, respectively. Even as far north as Alberta some pigeons nest in midwinter (McGillivray 1988).
Migration: The Domestic Pigeon is nonmigratory but seen occasionally in transit, flying over native habitats, as in El Capitan Open Space Preserve (N15) 8 April 2001 (P. Unitt). A few such records could represent birds using nearby natural cliffs (four near Garnet Mountain, N22, 24 May 1997, G. L. Rogers; one near the summit of Otay Mountain, U15, 1 April 2001, P. Unitt).
Winter: In winter Domestic Pigeons gather into larger flocks than in spring and summer, up to 620 in Escondido (J10) 22 December 2000 (W. E. Haas). The Domestic Pigeon has a slightly wider distribution in winter: we recorded it in 42 atlas squares in winter but not the breeding season versus 24 for the converse. We noted the species only a few times flying over more or less wilderness areas, for example, six near Margarita Peak (B5) 31 January 1998 (W. E. Haas), one at 4200 feet elevation in Henderson Canyon (E23) 26 February 2002 (R. Thériault), and ten near Garnet Peak (N22) 10 December 1997 (G. L. Rogers).
Conservation: Urban development, of course, creates new habitat for Domestic Pigeons, but newer buildings are designed to discourage them, and some older ones have been retrofitted with porcupine wire to the same end. Even though the birds feed heavily on waste food left by people, farmland may on the whole offer better foraging than cities, so urbanization of former farmland may not benefit the birds. Except possibly at Borrego Springs, Christmas bird counts show no clear trend in Domestic Pigeon numbers in San Diego County since the species was included in the counts beginning in 1973.
Band-tailed Pigeon Patagioenas fasciata
California’s only native large pigeon can be seen year round in San Diego’s mountains, sometimes in large flocks, sometimes as only scattered individuals. Elderberries and acorns are its staple foods, so the Band-tailed Pigeon frequents woodland with abundant oaks. Though it inhabits all the mountains where the black and canyon live oaks are common, its distribution is oddly patchy in foothill woodland dominated by the coast live oak. Both migratory and nomadic, the Band-tailed Pigeon may be common in some areas in some years and absent in others; it shows up occasionally in all regions of the county as a vagrant.
Breeding distribution: As its name in Spanish suggests, Palomar Mountain is the center of Band-tailed Pigeon abundance in San Diego County (paloma = pigeon or dove). The pigeons move up and down the mountain, descending to the base in summer to feed on elderberries in dry scrub. Eleanor Beemer noted this movement at Pauma Valley in the 1930s, and it continues today. Some of our larger summer counts, including the largest, were in elderberries around the base of Palomar: 35 near Rincon (F13) 7 July 2000 (M. B. Mosher); 110 in Dameron Valley (C16) 23 June 2001 (K. L. Weaver). Most of the birds nest in the forested area high on the mountain, but some nest around the base, as shown by a fledgling in Pauma Valley (E12) 19 May 2001 (E. C. Hall) and an occupied nest near the West Fork Conservation Camp (E17) 12 May 2001 (J. O. Zimmer).
Band-tailed Pigeons occur throughout the county’s other mountains as well, with up to 40 on the south slope of Hot Springs Mountain (F20) 13 May 2001 (M. and B. McIntosh), 35 in Sherilton Valley, Cuyamaca Mountains (N19), 12 June 2001 (G. Wynn, P. D. Jorgensen), and 50 near the head of La Posta Creek, Laguna Mountains (P23), 3 June 1999 (E. C. Hall, J. O. Zimmer).
At lower elevations, in northwestern San Diego County Band-tailed Pigeons appear to be regular in small numbers around Rainbow (C10; up to 12 on 21 April 1999, D. C. Seals) and in much larger numbers in the Santa Margarita Mountains (up to 95 around De Luz, B6, 22 April 2000, K. L. Weaver). They spread over other areas of northwestern San Diego County irregularly. For example, K. L. Weaver found them irregularly common to absent during breeding-bird censuses along the Santa Margarita River east of Sandia Canyon (C8) from 1989 to 1994; in spite of thorough coverage he never recorded them there from 1997 to 2002. The Band-tailed Pigeon’s nesting in the Santa Margarita Mountains is confirmed by a fledgling in Cold Spring Canyon (A4) 17 June 2001 (J. M. and B. Hargrove).
In the foothills of central San Diego County there is considerable oak woodland that seems attractive to Band-tailed Pigeons, yet our only spring sighting in this area was of one pair in San Vicente Valley (L16) 27 April 2000 (J. D. Barr). Then in the southern third of the county the pigeon recurs in this habitat, occurring in small numbers at elevations as low as 1400 feet in Peutz Valley north of Alpine (P16; up to two on 11 July 1999, P. Unitt). We found the species consistently in an enclave slightly isolated from the rest of the range from Lawson Creek south to Lyons Peak (R16/R17/S17), with up to nine in Lawson Valley (R17) 29 March 1999 (J. R. Barth). This population may be of long standing, as A. O. Treganza collected a Band-tailed Pigeon egg from Lyons Peak 12 March 1929 (WFVZ 28947)—the southernmost confirmed nesting ever of subspecies P. f. monilis. From 1997 to 2002 the southernmost likely site of Band-tailed Pigeon nesting was near Morena Butte (T21), where R. and S. L. Breisch noted three juveniles 5 July 1997. One 0.8 mile southeast of Music Mountain (U27) in April 1997 sang regularly for four to five weeks but never attracted a mate and was in marginal habitat (F. L. Unmack), as was another nearby in Jewell Valley (U26) 6 July 1993 (P. Unitt).
Nesting: Band-tailed Pigeon nests are difficult to find; over five years we noted only eight. The nest is placed on a tree branch, often quite high in the tree. Conifers may offer better nest sites than do oaks, accounting for the pigeon’s occurring principally in mixed coniferous/oak woodland. But the birds nest in oaks as well: see Abbott (1927b) for a photograph of a nest of in a black oak at Mesa Grande (H17). The Band-tailed Pigeon usually lays only one egg per clutch but makes up for this low number with a long breeding season. Sharp (1919) and Abbott (1927b) reported several fall nests of the Band-tailed Pigeon in San Diego County, and fall nesting is common elsewhere too (Keppie and Braun 2000), probably stimulated by the ripening of acorns. The nesting activity we observed during the atlas period all falls well within the interval of 6 March-14 October based on collected eggs and literature reports.
Migration: In the northern part of its range the Band-tailed Pigeon is highly migratory. Some of these migrants reach San Diego County; pigeons banded in northern California have been recovered here (Keppie and Braun 2000). Occasional vagrants reach the coast at almost any season, most often in late spring and fall, less often in summer, and least often in late winter. Our only spring migrant toward the coast during the atlas period was one about 0.5 mile southwest of Morro Hill (F7) 27 April 1997 (A. Peterson), but there are over a dozen reports from Point Loma (S7) at various seasons, with up to 25 during May 1981 (G. McCaskie).
In the Anza–Borrego Desert there are eight records, two in April, one each in May and June, and two each in August and November. Most are of single individuals, but two birds were at Lower Willows (D23) 6 June 1974, and three were in Indian Gorge (P27) 20 November 1988 (ABDSP database). The only one in the desert during the atlas period was in the developed area of Ram’s Hill, Borrego Springs (H25), 20 April 2000 (R. Halford).
Winter: In spite of the Band-tailed Pigeon’s nomadism, the distribution we observed in winter was closely similar to that in spring and summer. Our maximum numbers in winter were somewhat larger, up to 167 at Volcan Mountain (I20) 17 December 2001 (R. T. Patton) and 175 coming to bait set out for turkeys in Green Valley, Cuyamaca Rancho State Park (N21), 25 February 1998 (P. D. Jorgensen). At low elevations in northwestern San Diego the pigeons occurred in almost exactly the same areas in winter as in summer, with an exceptional high count of 92 near Ross Lake (B7) 2 January 2002 (K. L. Weaver). The situation with the isolated population in the Lyons Peak region was parallel, with a maximum count of 11 between Lyons and Lee valleys (S16) 17 January 2000 (J. R. Barth).
From 1997 to 2002 we had four winter records of vagrants well outside the known breeding range, with five at the Vineyard golf course (K11) 1 December 1998 (E. C. Hall), one at Mount Woodson (L13) 3 January 1998 (D. Miller), two at Goodan Ranch County Park (N12) in December 1998 (local ranger fide M. and B. McIntosh), and one at Point Loma 15 December 2001 (J. C. Worley). Right along the coast the Band-tailed Pigeon is generally less frequent in winter than at other seasons, but the winter of 1989–90 broke this pattern. That year the species was reported widely, with up to 170, by far the largest flock of coastal vagrants reported, in Los Peñasquitos Canyon (N8) 18 January 1990 (B. Zepf, AB 44:329, 1990).
Conservation: Over California as a whole, the Band-tailed Pigeon was decimated by overhunting early in the 20th century (Grinnell 1913). In San Diego County the reduction may have been milder, as local naturalists were largely silent on this topic. Subsequent protection led to at least a partial recovery. Current trends are unclear because of the species’ inherent irregularity and the difficulty of devising survey methods applicable over diverse habitats (Keppie and Braun 2000). The pigeon’s biology entails relying on one food that is abundant at one season, then shifting to another food abundant at another season. If one link in this seasonal chain is broken, the pigeons could suffer even though the other links remain intact. For example, if development around the base of Palomar Mountain removes a substantial fraction of the elderberry trees, the carrying capacity of the entire Palomar range could be affected.
Taxonomy: Band-tailed Pigeons along the Pacific coast are P. f. monilis (Vigors, 1839), darker than the other subspecies in the United States and Mexico. It breeds from the Pacific Northwest south to San Diego County, apparently reaching northern Baja California as a nonbreeding visitor only.
Eurasian Collared Dove Streptopelia decaocto
Introduced from the Old World to the Bahamas, the Collared Dove spread to Florida then across the entire width of North America in less than 20 years (Romagosa and McEneaney 1999). There have also been independent releases in the United States, establishing local populations, such as one in southern California in Ventura County in the early 1990s (Cole and McCaskie 2004). Sightings in San Diego County are likely the results of birds arriving from the east, as the number in Calipatria, Imperial County, had built to over 50 by 2003. The first Collared Dove in San Diego County was one at Marina View Park, Chula Vista (U10), 29 May 2002 (G. McCaskie). Subsequently, up to two were at the Roadrunner Club, Borrego Springs (F24), from 12 April 2003 onward (M. B. Mulrooney), and one was in the Mission Hills area of San Diego (R8/R9) 28 September 2003 (D. Dobson). Colonization is inevitable; the Collared Dove is an urban bird.
Spotted Dove Streptopelia chinensis
When a plant or animal is released in a place where it is not native, often it dies out quickly because the new environment does not meet its needs. Sometimes, in the lack of its usual predators or other mechanisms of population control, it proliferates, becoming a pest or upsetting an ecological balance. And there are paths between these extremes, as exemplified by the Spotted Dove. Introduced from Asia to Los Angeles about 1915, the Spotted Dove multiplied and spread, arrived in San Diego County by 1950, and established itself here as an uncommon and local resident. But in the 1980s and 1990s it decreased, and with the turn of the century it died out completely.
Breeding distribution: From 1997 to 2001, in spring and summer, we found the Spotted Doves at only two sites in San Diego County. Though Encanto (S11) and Spring Valley (R12/S12) were long the center for the species in metropolitan San Diego, our only sighting in this area was of a single bird singing in Encanto 21 June 1997 (P. Unitt). In the north county, the only area where the Spotted Dove persisted into the atlas period was Rainbow (C9), where our single record during the breeding season was of two on 19 April 1999 (D. C. Seals).
Nesting: The Spotted Dove’s nesting habits are similar to those of other doves, with a flimsy nest and some breeding year round (Garrett and Walker 2001). Nesting in San Diego County was never well described.
Winter: We noted the Spotted Dove at Rainbow in winter as well as in spring with three on 28 January 1999 (D. C. Seals) and one on 18 February 2000 (K. L. Weaver). Our two other sightings in fall and winter, of one at Imperial Beach (V10) 2 November 1998 (P. Unitt) and one at O’Neill Lake (E6) 18 December 1998 (P. A. Ginsburg), represented wandering individuals rather than resident populations.
Conservation: The Spotted Dove was first reported in San Diego County on the Oceanside Christmas bird count 30 December 1950, when four were noted. The species first appeared on the San Diego count 26 December 1954. Sams and Stott (1959) reported it from Spring Valley, the Oceanside area, and Balboa Park, “among other places.” In San Diego County the Spotted Dove was always uncommon and local, never approaching the abundance it reached in metropolitan Los Angeles. All five county specimens in the San Diego Natural History Museum are from East San Diego or Spring Valley. Outside the coastal lowland the only reports are three from Borrego Springs (F24/G24), the last of six on 22 October 1996 (E. Jorgensen), and of one on the Lake Henshaw Christmas bird count 16 December 1991. Numbers on the San Diego Christmas bird count peaked at 9 on 29 December 1957; numbers on the Oceanside count peaked at 27 on 31 December 1977. By 1980, however, the species was declining. Marjorie and Don Hastings last noted it at their home in Spring Valley (R12) in 1989, and about that time other residents of Spring Valley called the San Diego Natural History Museum to inquire about the birds’ disappearance. The last record on any Christmas bird count was of two on the San Diego count 16 December 1995. It seems certain that the five-year atlas period, 1997–2002, saw the extirpation of the county’s resident population; if any more are seen, they are likely to be rare dispersers only.
The Spotted Dove’s reversal of fortune is not confined to San Diego County but has been noted widely in southern California (McClure 1992, Garrett and Walker 2001). The reasons for the decline are unclear. Garrett and Walker (2001) suggested predation by the increasing population of American Crows and increased density of urban development as contributing factors. The areas the doves colonized in San Diego County longest were of relatively low-density development or dominated by agriculture, but the birds have disappeared whether the land use has changed or not. The story of the Spotted Dove in California parallels that of some other birds like the Varied Tit (Parus varius) in Hawaii or the Crested Mynah (Acridotheres cristatellus) on Vancouver Island, introduced populations that thrived for decades but ultimately failed.
Taxonomy: Nominate S. c. chinensis was the subspecies of the Spotted Dove introduced to southern California.
White-winged Dove Zenaida asiatica
The White-winged Dove is a characteristic bird of the desert Southwest, at the edge of its range in eastern San Diego County. In the Anza–Borrego Desert it is common at oases and human settlements. Its numbers are on the increase, as part of a pattern that reaches from California to Florida. Formerly a summer visitor only to California, the dove is losing its habit of migration, establishing itself year round first in San Diego County and increasingly elsewhere in the Colorado Desert.
Breeding distribution: The White-winged Dove is found in all the developed areas of the Anza–Borrego Desert and at almost all of the oases, extending up canyons on the mountains’ east slope occasionally as far west as Banner (K21; six on 17 May 1999, P. K. Nelson). The largest numbers are at the oases of the southern half of the desert, with up to 150 at Vallecito County Park (M25) 16 May 2001 and 120 at Carrizo Marsh (O29) 11 May 2001 (M. C. Jorgensen). The grapefruit orchards at the north end of the Borrego Valley (E24) are the area of the next largest concentrations, with up to 50 on 11 June 2001 (P. D. Jorgensen).
In Arizona, White-winged Doves feed heavily on the nectar and fruit of the saguaro and may be able to meet their need for water from these sources. In the Anza–Borrego Desert, where there are no native saguaros, the doves probably must drink free water daily. The distance to which they will commute to water is not known precisely but may be at least 2 miles, about the distance to water from a nest along Carrizo Wash (O28) 31 May 2001 (P. D. Jorgensen). On rare occasions it may be farther, as suggested by one singing in Fish Creek Wash (M29) 1 May 2001 (J. R. Barth).
Nesting: The White-winged builds a typical dove nest, a flimsy platform of sticks, usually on a large branch or in the fork of a trunk. Nest sites atlas observers described were willow (twice), mesquite, palo verde, and California fan palm. The birds may nest colonially or as scattered pairs.
The White-winged Dove is noted for its midsummer nesting even in the hottest climate, as along the lower Colorado River (Rosenberg et al. 1991). In the Anza–Borrego Desert, where many White-winged Doves stay through the winter, the birds can start earlier, as they do in urban settings in Texas (Hayslette and Hayslette 1999). Our observations from 1997 to 2001 indicate that in San Diego County the doves lay from the beginning of April to early June. A notable exception was in the wet winter of 1998, when one was building a nest at Tamarisk Grove (I24) 27 January (P. K. Nelson)
Migration: In the Salton Sink, where at the beginning of the new millennium it was just starting to winter regularly, the White-winged Dove arrives mainly in April and departs mainly in August (Patten et al. 2003). Evidently some in the Anza–Borrego Desert still follow this schedule because the species is more widespread there in summer than in winter. Small numbers of stray migrants reach the coastal slope regularly in fall, less frequently in spring. At least 40 such migrants have been reported in spring, most frequently from Point Loma (S7), on dates ranging from 30 April (Point Loma, R. E. Webster, AB 36: 894, 1982) to 6 June (1966, Tijuana River valley, AFN 20:600, 1966). During the atlas period, at least one was at Point Loma 12–23 May 2001 (D. K. Adams) and one was at Chula Vista (U11) 4 May 2001 (A. Mercieca). Coastal migrants are considerably more frequent in fall than in spring, occurring annually with as many as 22 in 1982 (AB 37:224, 1983). A few are seen as they cross the mountains, such as one in Sherilton Valley (N19) 23 August–4 September 1999 (G. and R. Wynn) and one flying west over the Laguna Summit along Interstate 8 (Q22) 16 August 1986 (P. Unitt). Late August to mid September is the peak period for coastal White-winged Doves, but the species has been noted in the Tijuana River valley 3 July 1995 (B. Foster, NASFN 49:982, 1995) and at Point Loma 12 July 1985 (R. E. Webster), and occasional stragglers occur through the fall.
Winter: The White-winged Dove is more concentrated into the major oases and developed areas in winter than in summer. At some places the doves are as abundant in winter as in summer. But at others they are absent in winter. At Angelina Spring (I22), for example, where P. K. Nelson found the birds regularly in the breeding season, with up to 20 per day, he found none in winter. White-winged Doves are especially numerous at Agua Caliente Springs (M26), with up to 150 on 26 February 2000 (E. C. Hall); many winter also in Borrego Springs (up to 141 throughout the valley 19 December 1999, Christmas bird count)
Winter visitors to the coastal lowland are rare, now averaging fewer than one per year. From 1997 to 2002 there was only one, at Santee (P12) 7 January 2001 (S. D. Cameron).
Conservation: The White-winged Dove spread north and west into southeastern California as the Colorado River and Imperial valleys were converted to agriculture in the early 20th century (Rosenberg et al. 1991, Patten et al. 2003). It was first reported from the Anza–Borrego Desert at Yaqui Well (I24) in July 1946 (Krutzsch and Dixon 1947), and it was first reported wintering in 1956, with one at Agua Caliente Springs 4 January (AFN 10:282, 1956). By 1984 the largest number reported at any season was only 20 and the species was still uncommon (Unitt 1984). Numbers on the Anza–Borrego Christmas bird count increased abruptly beginning in 1991. During its first seven years, 1984–90, the count averaged 2.6; from 1997 to 2001 it averaged 87. Although the creation of new habitat in the form of farms and cities is probably responsible for the White-winged Dove’s northward spread, the colonists use natural habitat as well as artificial, as can be seen at the Anza–Borrego Desert’s oases.
Curiously, the number wintering in the San Diego area has peaked and declined. From 1965 to 1971 the White-winged Dove was found almost annually on the San Diego Christmas bird count with an average of 1.7. Yet none has been found on any Christmas count on the coastal slope since 1992. Perhaps the change is the result of the population in the Anza–Borrego Desert becoming more sedentary.
Taxonomy: Only the large, pale subspecies Z. a mearnsi Ridgway, 1915, occurs in California.
Mourning Dove Zenaida macroura
One of our most familiar birds, the Mourning Dove is common over most of San Diego County year round. The doves benefited from the arrival of western civilization; they are now more abundant in agricultural areas and suburbs than in native woodland or scrub. But they are found in all of the county’s habitats from the coastal strand to open montane coniferous woodland to the desert floor.
Breeding distribution: The Mourning Dove is tied with the House Finch for the title of San Diego County’s most widespread bird. Both species were missed in just two covered atlas squares; we failed to find the Mourning Dove only in two of the least-vegetated parts of the Anza–Borrego Desert. The dove is most abundant in the coastal lowland, especially in urban and agricultural areas, in Warner Valley (G19; up to 300 on 25 June 2000, P. Unitt), and at oases and in developed areas of the Anza–Borrego Desert (up to 250 in the orchard-planted region of the Borrego Valley, E24, 8 June 2001, P. D. Jorgensen). It is least abundant in the coniferous woodland of San Diego County’s higher mountains and in the drier regions of the Anza–Borrego Desert. The Mourning Dove needs to drink regularly, but evidently almost all of the Anza–Borrego Desert is within the distance the birds can commute to water daily. A nest with nestlings along Fish Creek Wash (L27) 13 April 2000, for example, was miles from the nearest known spring (M. B. Mulrooney).
Nesting: Mourning Doves nest in situations as diverse as their habitats, but most nests are in trees or large shrubs. Because the nest is so flimsy the birds often build it on the thicker branches. This preference for firm supports also leads the doves to use man-made sites like building eaves, bridge girders, and hanging flower baskets. Nests on the ground are fairly common, too, accounting for about 18% of all Mourning Dove nests atlas observers described (ground nests may have been commented on disproportionately often). Some ground nests were somewhat protected by being built under cacti or thistles, but others did not have even this defense.
One key to the Mourning Dove’s success is that in spite of laying only two eggs per clutch, it has a short nesting cycle, long nesting season, and nests repeatedly in a single year. Most nesting takes place from March to July, but activity outside this interval is not rare. In residential areas of San Diego, we noted a nest with eggs as early as 10 January 1998 and a recent fledgling on 7 February 2001, implying egg laying in early January. In late summer and fall, we noted nest building as late as 19 August 2000 and a fledgling as late as 16 October 1999, implying egg laying in early September. Sharp (1907) found eggs at Escondido as late as 2 September. In natural habitats the dove’s season is less extended, but in the wet spring of 1998 the birds began nesting in the Anza–Borrego Desert in the last week of February, when the earliest desert report was of an occupied nest near the Borrego Air Ranch (H26) 22 February (M. L. Gabel).
Migration: The Mourning Dove is highly migratory; the large flocks seen in winter may consist largely of winter visitors from the north. A few may be seen out of sight of land on almost every pelagic trip off San Diego in May and September. Birds banded at San Diego 3 January 1929 and 11 March 1929 were recovered at Boise, Idaho, 7 September 1929 and at Reno, Nevada, 10 September 1929, respectively (Lincoln 1936).
Winter: In the coastal lowland and inland valleys, the Mourning Dove is even more abundant in winter than in spring and early summer. Wintering birds often gather into large flocks, up to 600 along Dulzura Creek (T15) 5 February 1999 (D. W. Povey). At higher elevations, however, the dove is less common. In extensive chaparral, montane woodland, and sparse desert scrub the dove is rare to absent in winter, even where it is fairly common in spring and summer.
Conservation: Though the Mourning Dove’s population in the western United States has declined since the 1960s (Dolton 1993), in San Diego County the trend is likely flat to positive. With their buildings and trees, developed areas offer more nest sites than the natural scrub and chaparral they replace. The importation of water favors a bird that must drink. San Diego County Christmas bird counts show no clear trend.
Taxonomy: The pale Z. m. marginella Woodhouse, 1852, is the only subspecies of the Mourning Dove occurring in California.
Inca Dove Columbina inca
The history of the Inca Dove has been one of slow, steady spread to the northwest. The dove reached Tucson by 1872, Yuma by 1942, and the Imperial Valley by 1984. In San Diego County only a few pioneers have been noted yet, but colonization of the Anza–Borrego Desert at least is only a matter of time. In California, the Inca Dove is a commensal of man, living only in towns or rural ranchyards.
Migration: The Inca Dove is still known in San Diego from about eight records. The reason for the “about” is that some individuals may have been escapees from captivity rather than pioneers of the wild population. This was evidently the case with the single specimen from San Diego County, a bird wearing an unmarked anodized aluminum band, found dead in East San Diego (R10) 13 March 1994 (SDNHM 48791). The first individual seen in the county, in the Tijuana River valley 9 September–30 November 1974 (AB 29:122, 1975), preceded the range’s growth front so much that Garrett and Dunn (1981) raised the possibility of the bird’s being an escapee. A natural origin seems almost certain for the records for the Anza–Borrego Desert, of one in Borrego Springs (G24) 16 February–April 1992 (A. G. Morley, AB 46:315, 481, 1992), another nearby 22 December 1996 (P. D. Ache, NASFN 51:802, 1997), one at Butterfield Ranch (M23) 18 February–24 April 2000 (M. B. Mulrooney, NAB 54:221, 327, 2000), and two at the Roadrunner Club, Borrego Springs (F24), 20 June 2000 (M. L. Gabel). Records from the coastal slope are of one photographed in Spring Valley (R12) 3 February–12 May 1997 (M. and D. Hastings), one singing and photographed in the Hillcrest area of San Diego (R9) 1–9 June 2001 (J. W. Schlotte, P. Unitt, NAB 55:483, 2001), and one in Encinitas (K7) 22 July 2001 (L. E. and C. Taylor, NAB 55:483, 2001).
Common Ground-Dove Columbina passerina
In spite of urban sprawl, agriculture remains important in San Diego County. Orchards, nurseries, and rural ranchettes are the Common Ground-Dove’s principal habitat here. Indeed, agriculture is doubtless responsible for the dove’s colonization of San Diego County, which began in the 1950s. Currently, the ground-dove is common and increasing in the Anza–Borrego Desert, mainly in the Borrego Valley, and uncommon and more or less static on the coastal slope, mainly in the inland valleys of the north county.
Breeding distribution: In San Diego County, the Common Ground-Dove is most widespread in the region of northwestern San Diego County dominated by avocado and citrus orchards. In this region it uses riparian woodland as well as artificial habitats. During spring and summer we encountered up to 10 per day in this area, as along the San Luis Rey River between Rice Canyon and Pala (D10) 10 June 2000 (K. Aldern, M. Bache) and at Valley Center (G11) in April 1997 (V. Dineen). One was at Buena Vista Lagoon (H6) 26 May 1997 (D. Rorick), but otherwise records at this season are at least 7 miles inland and below 1500 feet elevation. In southwestern San Diego County the only site where the ground-dove is currently resident year round is Rios Canyon just east of Lakeside (P15), an area of avocado orchards (nine on 11 May 2001, C. G. Edwards).
In the Anza–Borrego Desert, the ground-dove is concentrated in the Borrego Valley, in both the area of grapefruit orchards in the north end of the valley (E24; up to 20 on 18 April 1998, P. K. Nelson) and in the residential areas of Borrego Springs (G24; up to 15 on 30 April 1997, P. D. Ache). It is evidently a permanent resident also in the mesquite thicket at Vallecito (M25), with up to five on 12 May 1999 (M. C. Jorgensen). Elsewhere in the Anza–Borrego Desert the ground-dove is irregular and not confirmed breeding, though this is possible, as the birds have been heard singing and seen in pairs, as at Yaqui Well and Tamarisk Grove (I24) 21 May 1998 (P. K. Nelson).
Nesting: Like other doves, the Common Ground-Dove builds only a minimal platform of twigs. Nest sites atlas observers described were in a palo verde, a tamarisk, a California fan palm, on an eave of a house, and inside a greenhouse. In the last, the eggs hatched on 25 July 1999, in spite of daily high temperatures in the shade at the nest ranging from 115 to 130° F, 10 to 20 degrees hotter than outside the greenhouse (P. D. Jorgensen).
The Common Ground-Dove has an unusually long breeding season, nesting repeatedly even if successful. Most nesting in San Diego County takes place from March through June, but a nest with nestlings in Borrego Springs (G24) 4 March 1997 (R. Thériault) and a fledgling on Hellhole Bajada (G23) 24 February 1999 (M. L. Gabel) translate to egg laying in mid February and late January, respectively. Even in the Anza–Borrego Desert the doves lay as late as the first half of July, as shown by a juvenile that fledged in Borrego Springs 27 July 1999 (R. Thériault) and the eggs that hatched in the greenhouse 25 July 1999. Morley (1959) reported ground-doves nesting in the Tijuana River valley as late as 2 October 1958, with one nest with eggs and another with young on that date.
Winter: The Common Ground-Dove gathers into small flocks when not breeding, probably accounting for reported numbers in winter being greater than those in spring and summer. The Anza–Borrego Christmas bird count has yielded up to 339 in the Borrego Valley on 16 December 2001, and the highest count in a single atlas square was 76 in Borrego Springs (F24) 19 December 1999 (P. K. Nelson et al.). On the coastal slope, the highest winter count by far was of 36 at De Luz (B6) 31 January 1998 (K. L. Weaver), where the birds were feeding on leftover seeds from old gourds in a gourd farm. Others counts on the coastal slope are of 12 or fewer.
The ground-dove is nonmigratory but disperses somewhat when not breeding, accounting for records a short distance from sites of residency such as one near San Marcos Creek and Questhaven Road (J8) 2 December 1998 (J. O. Zimmer), one at Ramona (K15) 30 December 2000 (D. and C. Batzler), and two in San Felipe Valley (I21) 27 December 1999 (W. E. Haas). The ground-dove was seen repeatedly in winter in Pamo Valley (J15), with up to seven on 2 January 1999 (I. S. Quon); it is probably resident here and just missed during the breeding season. The small population in Rios Canyon (P15) was found in winter as well as spring, with six on 28 January 2001 (C. G. Edwards).
Though formerly breeding fairly commonly in the Tijuana River valley (V10/V11), currently the ground-dove reaches that area only irregularly in fall and winter, presumably by dispersing north across the international border. The maximum reported there in winter during the atlas period was only four on 20 December 1997 (G. L. Rogers).
Conservation: Before 1957, the Common Ground-Dove was known in San Diego County only from five specimens, collected at San Pasqual “about 1900” (Willett 1912), 3 miles north of Escondido 29 June 1915 (Dixon 1916), in Mission Valley 10 November 1915 (Grey 1916, SDNHM 1887), at Lakeside 21 December 1923 (SDNHM 2846), and at Santee 28 February 1939 (SDNHM 18051). In 1957 the birds were discovered in the Tijuana River valley and confirmed nesting there the following year (Morley 1959, Sams 1959). The ground-dove apparently colonized northwestern San Diego County beginning in 1962; this was the first year it was recorded on the Oceanside Christmas bird count and noted at Pauma Valley by Eleanor Beemer, who observed birds there since the mid 1930s. In the Anza–Borrego Desert the first observation was in 1964 and the first recorded nest in 1972 (ABDSP database). Numbers in the Borrego Valley have increased steadily since—from 1984 to 1988 the average on the Anza–Borrego Christmas bird count was 60, whereas from 1997 to 2001 it was 217.
In the Tijuana River valley, however, the breeding population died out in 1984 after having persisted continuously since 1957. Presumably this change was the result of the steady encroachment of urbanization on both sides of the border, leaving the valley as a shrinking enclave of open space. Even though the ground-dove is a bird of modified habitats in southern California, it requires extensive open ground for foraging. It does not tolerate high-intensity development in which the earth is scraped, paved, and landscaped. The scenario in the Tijuana River valley warns that the ground-dove could be eliminated from northwestern San Diego County too, as agriculture gives way to urban sprawl. Conservation of riparian woodland benefits the ground-dove, too. Along the Santa Margarita River north of Fallbrook, the ground-dove population crashed in 1993, when floods washed away mature trees (K. L. Weaver).
Taxonomy: Common Ground-Doves in southern California are C. p. pallescens (Baird, 1860), as its name states a subspecies paler than others occurring farther east and south.
Ruddy Ground-Dove Columbina talpacoti
The Ruddy Ground-Dove is following in the footsteps of its relatives the Common Ground-Dove and Inca Dove, spreading north out of Mexico to colonize the southwestern United States. Since the first in 1984, the California Bird Records Committee has archived close to 100 occurrences in the state, with up to ten individuals at a time in Death Valley, a site of probable nesting. The species was confirmed nesting for the first time in California in the Imperial Valley in 2003 (McCaskie 2003). In San Diego County there are six accepted records.
Migration: Five of the San Diego County Ruddy Ground-Dove reports accepted by the California Bird Records Committee are from the Tijuana River valley in fall: one from 12 to 20 October 1988, up to two from 14 to 31 October 1989 (G. McCaskie, K. A. Radamaker; Patten and Erickson 1994), one on 8 September 1990 (G. McCaskie, Heindel and Garrett 1995), one on 23 October 1992 (Heindel and Patten 1996), and one on 18 October 1997 (G. McCaskie, T. R. Clawson, Rottenborn and Morlan 2000). The only spring record is of one photographed at Santee (P12) 16 May 1999 (M. B. Mulrooney, Rogers and Jaramillo 2002). A few other reports were rejected or not submitted.
As with almost every bird originating from mainland Mexico, there is a possibility that some of these Ruddy Ground-Doves were escapees from captivity. But the species’ surge north and west—even across the Gulf of California—is so well established that some of the San Diego County records must be part of this pattern.