Hummingbirds  — Family Trochilidae

Broad-billed Hummingbird Cynanthus latirostris

Largely a Mexican species, the Broad-billed Hummingbird breeds no closer to California than southeastern Arizona.  Yet it has crossed the Colorado River as a vagrant to California over 75 times, yielding 16 more or less well-supported records for San Diego County, all in fall and winter.

Migration: Eight of San Diego County’s Broad-billed Hummingbirds have occurred in fall between 9 September and 9 November.  Of these, one was at Point Loma 22 October 2001 (R. E. Webster, Garrett and Wilson 2003), seven were in the Tijuana River valley (two on 9 November 1963, single birds 14 October 1962, 20–23 September 1977, 8–9 October 1981, 9–11 September 1983, and 5–8 October 1997). 

Evidence for all but those in 1963 has been submitted to and accepted by the California Bird Records Committee.  The committee rejected a spring report published in American Birds (Patten et al. 1995b).

Winter: The county’s nine winter records of the Broad-billed Hummingbird, from 10 November to mid March, are more widely scattered.  Seven are from the coastal lowland, from San Diego mid November 1961–mid March 1962 (Dunn 1988), from Spring Valley (R12) 8–10 March 1979 (M. Thornburgh, AB 33:314, 1979), from Balboa Park (R9) 28 November 1979–29 February 1980 and returning in at least four of the five subsequent winters (Bevier 1990), from Rancho Santa Fe (L8) 18 December 1982–15 January 1983 (L. R. Santaella, AB 27:339, 1983), from Coronado (S9) 11 January–28 February 1986 (R. E. Webster, Bevier 1990), from San Elijo Lagoon 5–10 January 1998 (M. B. Stowe, R. T. Patton, Erickson and Hamilton 2001) and from Upper Otay Lake (U13) 12 December 1999–10 March 2000 (G. Morse, D. Griffin, McKee and Erickson 2002).  Two records are from Agua Caliente Springs (M26) in the Anza–Borrego Desert, 16 January–10 February 1977 (G. McCaskie, Luther 1980) and 15–21 March 1982 (D. Dewey, AB 36:894, 1982).

Taxonomy: No specimen is preserved from San Diego County (or anywhere in California), but the birds at Balboa Park and Upper Otay Lake were photographed.  Presumably the subspecies reaching us is C. l. magicus (Mulsant and Verreaux, 1872).

 

 

 

Xantus’ Hummingbird Hylocharis xantusii

The exquisite Xantus’ Hummingbird is endemic to Baja California, resident from Cabo San Lucas north to the Sierra San Francisco, still over 350 miles south of the international border.  Nevertheless, there are three records of vagrants farther north, one from British Columbia (Toochin 1998), one of a female that, despite the lack of a male, built a nest in Ventura County (Hainebach 1992), and one rather shaky report of a male from the Anza–Borrego Desert.

Winter: Richard Klauke of Alberta reported a male at Yaqui Well (I24) 27 December 1986.  Although the record has been accepted by the California Bird Records Committee (Pyle and McCaskie 1992, McKee and Erickson 2002), the bird was seen by only a single observer who did not take notes at the time of the observation.

Violet-crowned Hummingbird Amazilia violiceps

The breeding range of the Violet-crowned Hummingbird barely extends across the Mexican border into extreme southeastern Arizona, and the species is one of the rarest vagrants to California, with only five records through 2002.  One of these is for San Diego County, of a bird that remained for an entire month, to be seen and enjoyed by over 500 spectators.

The Violet-crowned’s combination of features is not shared with any other hummingbird recorded north of the Mexican border: black-tipped red bill, bronze-green upperparts, and entirely whitish underparts.  The violet of the crown may be subdued and inconspicuous, not contrasting strongly with the back.

Migration: The single record of the Violet-crowned Hummingbird in San Diego County is of one that stayed around the home of Frank and Betty Scheible in Carlsbad east of La Costa (J9) from 3 November to 3 December 1996 (C. Mann, A. Klovstad; McCaskie and San Miguel 1999).  Abundant flowers of the Cape honeysuckle sustained the bird.  The Scheibles graciously opened their home to the crowds of eager birders from throughout California who arrived to see this cooperative visitor.

Taxonomy: Though there are no specimens of the Violet-crowned Hummingbird from California, photographs strongly suggest the greenish-tailed northern subspecies A. v. ellioti (Berlepsch, 1889).

Magnificent or Rivoli’s Hummingbird Eugenes fulgens

 

This large hummingbird breeds in high mountains north to central Arizona and is partially migratory.  But until 2003 the only reports from California were inadequate for giving the species a place on the state bird list.  Then, within months of each other, two appeared, both well photographed: the second in Eureka, the first in San Diego.

Migration: California’s first well-documented Magnificent Hummingbird was an immature male at Kate Sessions Park (Q8) 11 October 2–29 November 2003 (N. Shrout).

Black-chinned Hummingbird Archilochus alexandri

Unlike Costa’s and Anna’s Hummingbirds, the Black-chinned has a rather conventional biology, occurring in San Diego County as a fairly common migrant and summer resident, in the latter role mainly in riparian and oak woodland.  Like other hummingbirds the Black-chinned feeds on nectar, but its special relationship to a plant is not for food but for nesting material.  Fuzz from the leaves of the western sycamore is typically the basis of the Black-chinned Hummingbird’s nest, and the abundance of the hummingbird seems to parallel that of the sycamore.

Breeding distribution: The Black-chinned Hummingbird is fairly widespread over San Diego County’s coastal slope but strongly concentrated in the county’s northwest corner.  In this region it can be quite common, with daily counts as high as 33 along the Santa Margarita River north of Fallbrook (C8) 24 May 2001 (K. L. Weaver).  Weaver’s breeding-bird censuses of an 11.7-hectare plot of riparian woodland in this area revealed four to nine females each year from 1989 to 1994 (average 0.5 per hectare).  In coast live oak woodland the density is even higher; a census of this habitat in the Santa Margarita Ecological Reserve (C9) in 1989 yielded 1.8 per hectare (Weaver 1990).  Farther south and east the species becomes more localized to the larger riparian strips in the coastal lowland and groves of oak woodland in the foothills.  Few Black-chinned Hummingbirds occur above 3500 feet elevation, and the species is largely if not completely absent as a breeding bird from the Campo Plateau east of Pine Valley and Campo.  Yet it breeds rarely even as high as 5500 feet on the north slope of Hot Springs Mountain (active nest 19 June 1999, K. L. Weaver, C. R. Mahrdt).  The apparent breeding range barely spills over onto the desert slope at San Ignacio at the head of the middle fork of Borrego Palm Canyon (one on 18 June 1999, K. L. Weaver, C. R. Mahrdt) and in upper San Felipe Valley (two at the south base of Cerro de la Hechicera, H20, 23 May 1999, A. P. and T. E. Keenan; one near Paroli Spring, I21, 26 April 1999, J. O. Zimmer).

Nesting: To build their nests, female Black-chinned Hummingbirds gather plant down and mat it together with spider webs.  The fuzz from the blades and petioles of sycamore leaves are the dominant material in San Diego County, giving the nest the golden-buff color of that fuzz.  The amount of lichen and other flaky material used to decorate the nest is variable but is often little or none, making the nest look like a smooth orange sponge.  But the birds use the fluff from willow and cottonwood trees as well, sometimes to the exclusion of sycamore fuzz, so we noted some grayish-white nests too.  Not surprisingly, we noted many nests in sycamore trees but even more in coast live oaks.

            Our observations from 1997 to 2001 corresponded to egg laying from late April to the beginning of July, the same interval documented by 96 egg sets collected in San Diego County from 1895 to 1942.

Migration: The Black-chinned Hummingbird’s spring migration takes place largely in April.  From 1997 to 2001, the earliest date reported ranged from 15 March (2001, two at Whelan Lake, J. Smith) to 2 April.  The Black-chinned Hummingbird is a rare migrant through the Anza–Borrego Desert, recorded as late as 12 May (1997, three at Agua Caliente Springs, M26, E. C. Hall) and 21 May (1995, one at Lower Willows, D23, L. Clark, C. Sankpill).  At the latter location, a riparian oasis, the species could nest irregularly.

            Fall migration begins by 11 July with reports from nonbreeding localities on that date from Bucksnort Mountain (C20) in 1999 (P. Flanagan) and Cuyamaca Rancho State Park (N20) in 1998 (B. Siegel).  Fall migration peaks in late August and early September.  Adult males depart in August, weeks before the last females or immatures are seen (and heard) in early October.  The latest recorded dates are 10 October (1981, Tijuana River valley, E. Copper, AB 36:218, 1982) and 12 October (1980, one at Point Loma, AB 35:227, 1981).

Winter: The Black-chinned Hummingbird is casual in California in winter, not yet confirmed with a specimen.  Most reports are likely misidentifications.  The best-supported records are of birds, none adult males, identified by call by observers aware of the species’ rarity at this season.  In San Diego County such records are of one at La Jolla 13 January 1990 (J. O'Brien, AB 44:330, 1990), two at Point Loma 28 December 1986 (J. Oldenettel, AB 41:330, 1987), and six in Balboa Park, although four of these are likely of a single individual that returned annually to the same canyon from 1979 to 1982 (AB 27:339, 1983).  All wintering birds were in ornamental trees including flowering eucalyptus.

Conservation: In contrast to Anna’s and Costa’s, the Black-chinned Hummingbird has undergone no obvious changes in its distribution or abundance in San Diego County.  Breeding birds have moved into developed areas built over former sage scrub on only a small scale, where sycamores or cottonwoods have been used in landscaping, as in Greenwood Cemetery, San Diego (S10) or Hilltop Park, Chula Vista (U11).  Where native trees have been retained amid low-intensity development, the Black-chinned Hummingbird remains, though it may be outcompeted by Anna’s Hummingbird around feeders, as is Costa’s (Stiles 1973).

Anna’s Hummingbird Calypte anna

Few birds have taken to man-made surroundings more thoroughly than Anna’s Hummingbird.  In its range, Anna’s is by far the most abundant hummingbird in gardens and at feeders while still remaining common in native sage scrub, chaparral, and riparian and oak woodland.  Where feeders and ornamental plants fuel it year round, Anna’s Hummingbird is a permanent resident; in natural habitats, many birds depart for the fall.  During winter they return, and some begin nesting as early as December.  Anna’s Hummingbird nests earlier than any other San Diego County bird.

Breeding distribution: Anna’s Hummingbirds breed widely over San Diego County, lacking only in the more sparsely vegetated parts of the Anza–Borrego Desert.  But they are most abundant in the coastal lowland and lower foothills.  High counts come from both heavily urbanized areas (41 in Pacific Beach, Q7, 1 June 1997, J. C. Worley) and native habitats (40 in Boden Canyon, I14, 24 April 2000, R. L. Barber).  It is likely that many of the Anna’s Hummingbirds seen in the mountains in summer are postbreeding dispersers from lower elevations.  Nevertheless, some do nest in montane forest, as illustrated by a female building a nest about 4200 feet elevation at Heise County Park (K20) 19 May 1998 (E. C. Hall) and by fledglings at about 4500 feet elevation in Lower Doane Valley (D14) 12 July 1998 (J. O. Zimmer) and about 4000 feet on Volcan Mountain (J20) 24 June 2001 (A. P. and T. E. Keenan).

            In the Anza–Borrego Desert Anna’s Hummingbird is locally common in developed areas, with up to 17 in the north Borrego Valley (E24) 12 March 2000 (P. D. Ache).  We confirmed the species’ nesting in all desert atlas squares with substantial agricultural or residential development, as well as in many canyons draining the desert slope of the mountains.  In other parts of the desert Anna’s Hummingbird is rare and much outnumbered by Costa’s.  Nevertheless, occasional birds nest in the desert far from oases: we found nests with nestlings in Smoke Tree Wash (E28) 25 April 1997 (P. D. Jorgensen), in upper Pinyon Canyon (K26) 9 May 2000 (E. Jorgensen), and in Smuggler Canyon (L25) 15 February 1999 (R. Thériault).

Nesting: Anna’s Hummingbirds build their nests mainly of plant fluff bound together with spider web.  The action of the female in collecting spider webs, grabbing a strand, backing up by about a foot, moving in to grab another strand, and repeating the cycle several times, is so characteristic that it proved an easy way to find nests.  The nest is typically decorated or camouflaged with flakes of lichen and dead leaves, sometimes of paint (Maender et al. 1996).  The sites in which the birds build are so diverse that a pattern is difficult to discern.  They make little effort to conceal the nest, usually protecting it only by placing it on slender twigs that terrestrial predators cannot negotiate.

If trees are in a female’s territory, she appears to prefer them over shrubs as nest sites, but in treeless habitats the birds nest in many other plants, including small shrubs.  Eleven of 12 nests found by M. A. Patten and colleagues in sage scrub around San Diego in 2001 and 2002 were in laurel sumac.  In urban areas man-made artifacts are common nest sites.  Perhaps the most extreme site described by atlas observers was a nest with nestlings in full sun atop a chain-link fence (M. and B. McIntosh).

            Our observations from 1997 to 2001 show that mid February to early June is the season when most Anna’s Hummingbirds nest in San Diego County.  Nevertheless, a minority of the birds in the coastal lowland start earlier, some as early as the third week of December.  Our earliest observation of nest building was at Guajome Lake (G7) 18 December 1998 (P. A. Ginsburg), and a nest with nestlings at Del Mar (M7) 5 January 1998 (L. Ellis) implies egg laying no later than 20 December.  A nest with one egg and one recently hatched chick at Old Mission Dam (P11) 31 December 1974 (J. L. Dunn) must have been started about 15 December, and a recent fledgling being fed by its mother in the Tijuana River valley (V11) 13 December 1998 (G. McCaskie) must have come from an egg laid about 7 November.  Our observations of eggs, nestlings, and fledglings suggest that egg laying ends rather abruptly in late June, yet on six occasions we noted nest building from 30 June to 1 August; perhaps these late attempts are aborted.

Migration: Our field schedule for this atlas, with an off season from August to November, was not well situated to detect seasonal changes in Anna’s Hummingbird’s distribution or abundance.  The species is scarce in natural habitats during the fall dry season, and migration between California and Arizona is confirmed on the basis of one band recovery (Russell 1996).  Yet there are records from late summer through fall from oases and irrigated areas in the Anza–Borrego Desert, up to 10 at the Roadrunner Club, Borrego Springs (F24), 10 October 1992 (A. G. Morley).  In San Diego County’s mountains Anna’s Hummingbird increases noticeably from December to January (see under Winter).  In urban areas the species is common year round, though individuals may move.

Winter: From December through February Anna’s Hummingbird is about as widespread in San Diego County as in spring and summer but even more concentrated in the coastal lowland.  We found it somewhat more widespread in the Anza–Borrego Desert in winter but sparse or lacking at the higher elevations.  In 28 squares encompassing the county’s higher mountain ranges, we noted Anna’s Hummingbird only seven times in December (maximum two individuals per day) versus 27 times in January (maximum 12 per day on 31 January) and 32 times in February (maximum 25 per day).  Three Anna’s Hummingbirds had returned to the summit of the county’s highest peak, Hot Springs Mountain, by 13 February 1999, when there was still much snow and no plants in bloom (K. L. Weaver).

Conservation: The proliferation of exotic nectar-bearing plants like eucalyptus, tree tobacco, and Cape honeysuckle, not to mention thousands of hummingbird feeders, has allowed the population of Anna’s Hummingbird to increase enormously and extend its range (Zimmerman 1973).  Sharp (1907) and Dixon (1912) considered the Black-chinned and Costa’s Hummingbirds more numerous than Anna’s at Escondido; now Anna’s surpasses them not only in man-made habitats but in many natural ones as well.  The increase continued into the 21^st century.  The San Diego Christmas bird count, for example, averaged 324 Anna’s Hummingbirds from 1966 through 1975 but 875 from 1997 through 2001, though the number of party-hours per count was 222–223 for both intervals.  All other counts in the county also show increases, except for Lake Henshaw, where there is great annual variability.  Bolger et al. (1997) found Anna’s Hummingbird to be more common along the interface between urban development and native scrub in metropolitan San Diego than in native habitat away from development.

Costa’s Hummingbird Calypte costae

Some birds’ lifestyle is to find a territory that can support them reliably and defend that territory as long as they can.  Other species—like Costa’s Hummingbird—find abundant but ephemeral resources, exploit them while they last, then move on.  Where flowers bloom in abundance, Costa’s Hummingbirds gather in numbers, then disappear as the flush fades.  The birds capitalize on the desert’s bloom in late winter and spring, that of sage scrub and chaparral in spring and summer, especially where wildflowers proliferate following a fire.

Breeding distribution: Costa’s Hummingbirds breed over most of San Diego County though not at the same time in all regions.  They occur throughout the Anza–Borrego Desert, where they are common in spring (up to 50 near Whitaker Horse Camp, D23, 12 April 1999, P. Unitt).  Their abundance varies with rainfall and the abundance of flowers that follows.  Our count per hour in eastern San Diego County varied from 0.96 in the wet 1998 to 0.38 in the dry 2000.  In the desert, alluvial slopes, with their rich flora, offer the best habitat to Costa’s Hummingbird, while valley floors dominated by halophytes offer little.  As a food source the chuparosa, with its longer flowering season, is the most important shrub to Costa’s Hummingbird in the Anza–Borrego Desert (Stiles 1973).  Ocotillo, desert lavender, desert thorn, and desert “willow” are also important, and the birds feed on many other plants as well.

            On the coastal slope Costa’s Hummingbird is also widespread, more abundant in the inland valleys and foothills than in the higher mountains or along the coast (up to 60 near Tule Springs, N18, 2 July 2001, J. R. Barth, E. C. Hall, A. P. and T. E. Keenan).  In mature sage scrub and chaparral Costa’s Hummingbird is fairly common, especially where white sage and Cleveland sage are common.  Cox (1981) suggested that Cleveland sage is specialized for pollination by Costa’s Hummingbird.

            A study comparing recently burned and mature chaparral near Pine Valley revealed that Costa’s Hummingbirds move into recovering burned chaparral in large numbers when the habitat is still dominated by herbs and subshrubs, especially woolly bluecurls, vinegar weed, showy penstemon, sticky nama, and the slope semaphore or wide-throated yellow monkeyflower.  Following heavy rain in the winter of 1992–93, these plants bloomed so profusely on recently burned slopes that the hillsides they covered looked purple from distances over a half a mile.  Costa’s Hummingbird was the most abundant bird in these areas, yet in the following years, as chaparral shrubs recovered, the fire-following plants dwindled and the number of Costa’s Hummingbirds fell in tandem.   In spite of the brevity of this irruption, the influx sufficed to make Costa’s Hummingbird the sixth most common bird in the recently burned areas according to point counts from 1993 to 1997 (Cleveland National Forest data).

Nesting: Female Costa’s Hummingbirds build a typical tiny hummingbird nest, well decorated with flaky material, making no effort to conceal it.  Even on the floor of the Anza–Borrego Desert nests are often placed in full sun.  The diversity of nest sites atlas observers described is too great to list, but in chaparral the birds often use the dead flowering stalks of Yucca whipplei.  After they have burst open and dried, the yucca’s fruits make an ideal tripod for supporting the nest.  We also found, however, numerous nests in trees, including coast live and Engelmann oaks, cottonwood, and sycamore, habitats where the Black-chinned and Anna’s Hummingbirds occur alongside Costa’s.

            Costa’s Hummingbird’s breeding seasons in the desert and chaparral differ yet overlap.  In the Anza–Borrego Desert the species lays primarily from February through April.  Even earlier nesting is possible, perhaps when the birds are stimulated by early rains, as attested by a nest with eggs at Truckhaven Rocks (F28) 9 November 1986 (P. D. Jorgensen) and a nest with nestlings in the Borrego Valley 3 February 1962 (Bakus 1962).  Our latest desert nest, in Borrego Springs (G24), had eggs on 18 May 1999 (P. D. Ache).

            On the coastal slope, Costa’s Hummingbirds lay mainly from mid April to mid June.  The activity we observed in this area from 1997 to 2001 agrees closely with the interval of 13 April–13 June attested by 26 egg sets collected from 1895 to 1952, except for two exceptionally early records: an occupied nest in Spring Valley (R12) 1 December 1999 (M. and D. Hastings; not shown on chart) and a nest at the Chula Vista Nature Center (U10) in which the eggs hatched 22–23 February 2001 (B. C. Moore).

Migration: The movements of Costa’s Hummingbird are complex and unconventional, as outlined by Baltosser (1989).  In the Anza–Borrego Desert the species arrives in numbers by December, remains common through May, and departs largely in June.  On the coastal slope the bulk of the population arrives in April and remains into July.  The species is seen rarely at oases in the Anza–Borrego Desert through the fall.  Its status in native habitats on the coastal slope at that season is still unclear, but the birds are seen in urban gardens in fall, perhaps more often at other times of the year.

Winter: Because most Costa’s Hummingbirds return to the Anza–Borrego Desert before 1 December, the distribution we recorded there during winter was similar to that in spring.  The main exception was at the higher elevations of the Santa Rosa and Vallecito mountains, where the species was lacking before March.  The Anza–Borrego Christmas bird count commonly yields the highest return of Costa’s Hummingbird of any such count in the United States, up to 157 on 19 December 1999.  During the atlas period the species’ numbers in desert in winter varied with rainfall in the same way as in the breeding season; the birds responded immediately by arriving in larger numbers in the wet winter of 1997–98.

            On the coastal slope, wintering Costa’s Hummingbirds are uncommon and local, rarely occurring above an elevation of 1500 feet.  Many of the birds wintering in the coastal lowland are in flowering ornamental vegetation, but some frequent sites of native semidesert scrub.  Most records from sites at higher elevations, such as Dameron Valley (C16; one on 12 December 1998, K. L. Weaver) and Pamo Valley (I15; up to three on 30 December 2000, M. Dudley), are from such habitat, shared with occasional visitors of other species more typical of desert like Scott’s Oriole and Brewer’s Sparrow.  Following the call of two Costa’s Hummingbirds at the south base of Spangler Peak (L15) 17 December 1998 led me to a patch of chuparosa, scarce on the coastal slope.  The garden in the San Diego Wild Animal Park featuring the plants of Baja California is the most consistent site for Costa’s Hummingbird on the Escondido Christmas bird count.

Conservation: Any long-term trends in Costa’s Hummingbird numbers are difficult to discern because of the species’ inherent irregularity.  Like other hummingbirds, Costa’s readily exploits feeders and ornamental plants.   The tree tobacco, an exotic plant that proliferates in disturbed open areas, has become an important food source for Costa’s and other hummingbirds and has even allowed Costa’s to extend its range (Baltosser 1989).  All the early writers found Costa’s Hummingbird on San Diego County’s coastal slope only in spring and summer.  On the San Diego Christmas bird count, it was first noted in 1956; since 1980 the count has yielded an average of 20.  Urban areas may be a refuge for the species in fall, allowing some to dispense with the need to migrate south or east to regions of summer rain.  Nevertheless, urbanization is not an unmitigated boon to Costa’s Hummingbird.  Anna’s Hummingbird appears far better adapted to the relatively static environment of urban gardens.  Anna’s has increased greatly, and that larger species dominates and displaces Costa’s at food sources (Stiles 1973).  On the basis of surveys from 11 April to 1 June 1993, Bolger et al. (1997) reported Costa’s Hummingbird to be sensitive to habitat fragmentation around metropolitan San Diego.  This finding may be due at least in part, however, to a natural preference for sunnier climate; atlas results show the species tends to avoid the coastal strip, commonly blanketed with low clouds in late spring and early summer.  The points in fragmented habitat surveyed by Bolger et al. tended to be closer to the coast than those in unfragmented habitat.

Calliope Hummingbird Stellula calliope

North America’s smallest bird breeds in western coniferous forests and winters in central Mexico.  At the latitude of San Diego County, its usual nesting habitat lies at an elevation higher than the tops the county’s highest mountains.  Thus it occurs in San Diego County mainly as a rare spring migrant.  A few birds have occurred in summer on Palomar and Hot Springs mountains and even engaged in courtship displays, but the species’ nesting in the county has not yet been confirmed.

Migration: The Calliope Hummingbird is seen in San Diego County mainly in April, occasionally as early as the last week of March.  Exceptionally early records are of one in Presidio Park (R8) 5 March 1976 (AB 30:892, 1976) and one that struck a window in downtown San Diego (S9) 18 February 2000 (L. van Epps, NAB 54:221, 2000, SDNHM 50375).  During the atlas period our latest was one at Point Loma (S7) 16 May 2001 (G. C. Hazard); in previous years the species was reported as late as 24 May (1982, one in the Tijuana River valley, T. Meixner, AB 36: 894, 1982) and 25 May (1985, one at Point Loma, C. G. Edwards).

            Numbers of Calliope Hummingbirds passing through San Diego County vary somewhat from year to year.  Usually the species is rare and seen singly, but Point Loma has been the site of concentrations as large as 15 on 30 April 1989 (J. Oldenettel, AB 43:537, 1989).  In the exceptionally dry spring of 2002 Calliope Hummingbirds, like some other migrants, concentrated in irrigated ornamental plantings in San Diego and were reported continuously from 9 March to 20 May with up to 12 per day (R. E. Webster, NAB 56:357, 2002).  The species is encountered most frequently along the coast, especially at Point Loma, but occurrences are scattered over the coastal slope.  In the Anza–Borrego Desert the only records are of one along Coyote Creek 26 March 1979 (B. Cord), one in nearby Box Canyon (C23) 19 April 2000 (M. B. Mulrooney), one at the Borrego sewage ponds (H25) 20 April 2002 (G. C. Hazard), two at Yaqui Well (I24) 26 April 1984 (A. Baker), and two at nearby Tamarisk Grove 18 April 2002 (R. Thériault).

            The only fall record is of a single bird in the Tijuana River valley 26 September 1981 (E. Copper).  The Calliope Hummingbird migrates in a loop heading north along the Pacific coast, south along the Rocky Mountains (Phillips 1975), so the species is not expected in San Diego County in fall.  The route by which the bulk of the population crosses from mainland Mexico to the Pacific coast of the United States is not well known but probably largely north of San Diego County.

Breeding distribution: Before we initiated field work for this atlas, the only summer records of the Calliope Hummingbird in San Diego County were of a male displaying to a female on Hot Springs Mountain (E21) 24 June 1980 (Unitt 1981) and a male near the Palomar Observatory (D15) throughout July 1983 (R. Higson, AB 37:1028, 1983).  Thus the number of possibly breeding Calliope Hummingbirds we noted from 1997 to 2001 was a surprise.  On Hot Springs Mountain (E21), at 5040 feet elevation near San Ignacio, K. L. Weaver and C. R. Mahrdt noted one 18 May 2001.  Near the north base of the mountain, at 4850 feet elevation 3.1 miles north-northwest of the summit (D20), J. M. and B. Hargrove observed a male displaying to a female 10 May 1999.  Around High Point, Palomar Mountain (D15), at patches of scarlet bugler and scarlet larkspur, Weaver noted one 13–14 May 1999, two males and one female 20 May 2000, and one male and two females 12 July 2000.  Completely unexpected was his discovery of a male and female in a small glade at 1900 feet elevation in Marion Canyon on the southwest slope of Palomar Mountain (D12) 18 June 2001.  Nesting of the Calliope Hummingbird may be possible even in this area; it has been reported exceptionally from foothill oak woodland at 420 feet elevation in Placer County (Williams 2001).

Broad-tailed Hummingbird Selasphorus platycercus

The Broad-tailed is the common hummingbird of the Rocky Mountains, but San Diego County lies well outside its normal migration route.  None of the four records is supported by a photograph or specimen, so the species’ inclusion on the county’s bird list is dubious.  Though adult males can be identified easily if the characteristic trilled whine of their wings is heard, there is plenty of opportunity for misidentification of this species, as with all hummingbirds.

Migration: Guy McCaskie now questions his report of a male in the Tijuana River valley 8 September 1968 (AFN 23:109, 1969).  Other published records are of a male attracted to red balloons at a birthday party near the Palomar Observatory (D15) 11–12 July 1978 (R. Higson, AB 33:218, 1969), a male at Point Loma (S7) 14 September 1982 (R. E. Webster, AB 37:224, 1983), and a female at Point Loma 10 May 1986 (R. E. Webster, AB 40:524, 1986).

Rufous Hummingbird Selasphorus rufus

The Rufous, the world’s northernmost hummingbird, commutes annually between the Pacific Northwest and Mexico.  It passes through San Diego County in both directions, taking advantage of the bloom of desert flowers like ocotillo in spring, of mountain flowers like the scarlet bugler in late summer, and of exotic plants like eucalyptus and tree tobacco at both seasons.  Hummingbirds of the genus Selasphorus also occur as rare winter visitors, though hardly any of these are adult males.  Distinguishing the Rufous and Allen’s Hummingbirds in other plumages usually requires careful study of birds in hand.

Migration: The migrations of the Rufous Hummingbird are early, though not quite so early as those of Allen’s Hummingbird.  Spring migration begins in February (one at Quail Botanical Gardens, K7, 1 February 1999, R. Campbell; two at La Jolla, P7, 5 February 2000, L. and M. Polinsky), exceptionally late January (one male in Borrego Springs, G24, 23 January 1993, A. G. Morley; one at Valley Center 27 January 1974, AB 28:693, 1974).  Migration peaks in late March and early April.  Even then the species is usually uncommon, though large concentrations can be seen occasionally around flowering trees or shrubs.  Our largest numbers during the atlas period—up to 40 at Yaqui Flat 7 April 1998 (P. K. Nelson)—were along the east base of the mountains, a line of concentration for migrants crossing from the desert to the coast.  Rufous Hummingbird numbers in the desert, however, are irregular, perhaps varying with weather conditions.  The species can be seen more consistently in spring in the coastal lowland.  Most birds have continued north by the end of April, though stragglers have been seen as late as 12 May (1976, one male at Point Loma, S7, J. L. Dunn) and 16 May (1999, two at La Jolla, L. and M. Polinsky).  Spring specimens range in date between 1 March (1963, San Luis Rey, G6, SDNHM 3195; 1990, El Cajon, Q13, SDNHM 46608) and 30 April (1990, Point Loma, SDNHM 46887).

            Though the bulk of the population makes a loop route, returning south along the Rocky Mountains after heading north along the Pacific coast (Phillips 1975), many Rufous Hummingbirds also go south through southern California.  Because few of the birds at this season are adult males, especially after early July, the ratio between the Rufous and Allen’s is uncertain.  In the SDNHM collection, there are six specimens of fall migrant Rufous from San Diego County, five of Allen’s.   Specimen dates of the Rufous range from 19 July (1934, Balboa Park, SDNHM 16536) to October (no exact date, 1968, Point Loma, SDNHM 37615).  Sight records are as early as 22 June (1970, one banded at Point Loma, AFN 24:717, 1970) and 23 June (2000, one near Cutca Valley, C14, J. M. and B. Hargrove).  After peaking from July to early August, numbers of Selasphorus hummingbirds dwindle, with the latest seen typically in early October.  Fall migrants concentrate at patches of native wildflowers in the mountains (up to 30, including seven male Rufous, near the Palomar Observatory, D15, 12 July 2000, K. L. Weaver) and at exotic flowering plants in the coastal lowland (up to 65 at Quail Botanical Garden, K7, 7 July 1997, C. C. Gorman).  There are a few fall records of Selasphorus hummingbirds in the Anza–Borrego Desert, the maximum being up to six coming to feeders near the Borrego Palm Canyon campground (F23) 26 July–6 August 1989 (L. L. Jee).

Winter: A few Selasphorus hummingbirds winter in San Diego County annually, in exotic flowering vegetation, especially eucalyptus.  During the atlas period the number reported per winter varied from ten in 1998–99 to just one in 2000–01.  Most wintering Selasphorus hummingbirds are in parks, cemeteries, and well-landscaped residential areas in the coastal lowland, with up to three in La Jolla (P7) 3 January 1999 (L. and M. Polinsky) and eight on the San Diego Christmas bird count 20 December 1975.  A few wintering birds have been adult male Rufous, and an immature male from Carlsbad (I6) 14 January 1994 (SDNHM 48887) is a Rufous.

More surprising are three winter records from the Anza–Borrego Desert.  One, of a male Rufous in Borrego Springs (F24) 19 December 1999 (M. L. Gabel), was from an ornamental planting, but two have been from natural canyons, Glorieta Canyon (H24) 29 December 1985 (L. Grismer, M. Galvan) and Hellhole Canyon (G23) 1 January 1999 (A. G. and D. Stanton).

Conservation: The introduction of diverse exotic flowering plants has augmented the food supply for migrating hummingbirds and has allowed a few of the Rufous to cut short their long migration and winter in southern California.  The county’s first winter record of any Selasphorus hummingbird was on the San Diego Christmas bird count 2 January 1961.

Allen’s Hummingbird Selasphorus sasin

Breeding only in a slender strip along the coast of California and southern Oregon, Allen’s Hummingbird has a remarkably limited distribution.  A migratory subspecies breeding south to Ventura County passes through San Diego County on its way to and from a winter range centered on the mountains around Mexico City.  Preadapted to suburbia, a nonmigratory subspecies resident on the Channel Islands spread to metropolitan Los Angeles and southward through Orange County.  It has now reached San Diego County, where it was found nesting for the first time at San Onofre in 2001.

Migration: Allen’s Hummingbird is famous for its migrations being shifted early in the year; the earliest arriving Allen’s Hummingbirds are the first of any land bird in both spring and fall.  “Spring” migration takes place largely before the equinox marks the beginning of spring; “fall” migration begins before the summer solstice and concludes by the beginning of September.  As a spring migrant Allen’s Hummingbird is uncommon in San Diego County; from 1997 to 2001 there was no report of more than two per day.  A concentration as large as the 200 noted by G. McCaskie in the Tijuana River valley 15 February 1964 has never been approached since.  At this season the species occurs mainly in the coastal lowland, rarely in the Anza–Borrego Desert (only two reports 1997–2001), and rarely as high in the mountains as 4000 feet elevation (one in Corte Madera Valley, R20, 21 February 1999, D. Herron).  Specimens range in date from 18 February (1940, La Jolla, P7, SDNHM 18095) to 31 March (1961, Alpine, P17, SDNHM 30263), with one mist-netted and measured 10 April (1971, Point Loma, S7, G. McCaskie).  The early specimen date is not representative, however, because the species begins arriving in its breeding range in late January.  Sight records for San Diego County range from 16 January (1988, near San Diego, J. Oldenettel, AB 42:322, 1988) to 22 April (1997, one at the upper end of Sweetwater Reservoir, S13, P. Famolaro).  An unidentified Selasphorus hummingbird north of Lake Morena (S21) 10 January 1998 (S. E. Smith) was most likely an early Allen’s.  Two reports in May could be of misidentified Rufous Hummingbirds or pioneers of the nonmigratory subspecies.

            Allen’s Hummingbird is probably more numerous in San Diego County in summer as a southbound migrant than in late winter as it heads north.  But in summer adult males make up a smaller proportion of the population.  Because only adult males are identifiable in the field, high counts are concentrated during the last week of June and first week of July (at least 10 in Barker Valley, E16, 25–29 June 1997, D. Rawlins), the time when most adult males pass through.  Specimens of southbound migrants range from 30 June (1997, Mission Hills area of San Diego, R9, SDNHM 50045) to 1 September (1996, La Jolla, SDNHM 49586).  Sight records range from 3 June (2000, Horno Area, Camp Pendleton, R. Breisch; 1997, probable Allen’s along upper Pine Valley Creek, O21, R. A. Hamilton) and 4 June (1970, two banded at Point Loma, AFN 24:717, 1970) to 10 September (1998, Point Loma, P. A. Ginsburg).  At this season Allen’s Hummingbirds are scattered over the coastal slope but there are no reports from the Anza–Borrego Desert.

 Winter: Selasphorus hummingbirds are rare winter visitors in coastal San Diego County, and some percentage of these are Allen’s.  There are at least ten sight records of apparent adult males, all within 3 miles of the coast, from late November to early January, such as one that remained at Del Mar (N7) from fall migration to 26 December 1999 (B. C. Moore) and one at Point Loma 6 January 2002 (R. E. Webster, NAB 56:224, 2002).  More important, there are two specimens, from Coronado (S9) 29 November 1968 (SDNHM 37875) and La Jolla 22 December 1999 (SDNHM 50350), plus one mist-netted at Point Loma 1 January 1968 (AFN 22:479, 1968).

Breeding distribution: Allen’s Hummingbird was confirmed nesting in San Diego County for the first time in 2001, when John and Beverly Hargrove noted three, including a displaying male and a female gathering nest material, at San Onofre State Beach (C1) 20 January 2001.  In the same area, a territorial male had edged a few feet across the line from Orange County 18 May 1998, when P. A. Ginsburg observed one defending a clump of bottlebrush.

            Further knowledge of Allen’s Hummingbird’s colonization of San Diego County should be based on actual breeding behavior and observations in late May, during the brief window between the departure of the last Rufous Hummingbirds and the arrival of the first migratory Allen’s.

Nesting: Nesting in January, as seen at San Onofre, is expected for Allen’s Hummingbird in southern California.  On the Palos Verdes Peninsula, Los Angeles County, Wells and Baptista (1979) reported females attending nests or fledglings in all months of the year except September and October.

Conservation: On the California mainland, the Channel Islands subspecies of Allen’s Hummingbird was discovered nesting on the Palos Verdes Peninsula in 1966 and was common there by the following year (Wells and Baptista 1979).  From there the birds began spreading into the Los Angeles basin, reaching Orange County by 1980, when they were first found nesting at Newport Beach and Costa Mesa.  By 1997 they had spread south along the coast to Laguna Beach, less than 15 miles northwest of the San Diego county line (Gallagher 1997).  They use ornamental vegetation as least as much as native willow trees, so further spread south along San Diego County’s coast seems assured.

The primitive migration route for Allen’s Hummingbird was north at low elevations along the coast, then south at high elevations through the mountains, a strategy geared to the availability of flowers in each zone (Phillips 1975).  With the proliferation of exotic plants that flower over intervals different from those of native species, this constraint is relaxed.  The spread of the tree tobacco in particular appears to be allowing southbound Allen’s Hummingbirds to migrate at low as well as at high elevations.

  

Taxonomy: The two subspecies of Allen’s Hummingbird differ in size, especially bill length.  The migratory nominate S. s. sasin (Lesson, 1829) is smaller that the nonmigratory S. s. sedentarius Grinnell, 1929.  See Stiles (1972) for a key; identifying the bird’s age and sex is a necessary precusor to identifying the subspecies, as it is for distinguishing the Rufous and Allen’s as species.

            All specimens from San Diego County are sasin except for one collected at Point Loma 25 April 1971 (SDNHM 37764).  Note that the date of this early pioneer of sedentarius falls outside the normal migration schedule of sasin.