Residential ranges of the Xantus (cross-hatched) and white-eared (inked) hummingbirds. The arrowhead represents an extralimital breeding location of the latter. (Adapted from Howell and Webb, 1995)
None in general English use; Orejas blancas, Chupaflor orejiblanco (Spanish).
Breeds casually in the mountains of southeastern Arizona, and south through the forests of both eastern and western Sierras from Sonora, San Luis Potosi, and Tamaulipas, Mexico, south to Nicaragua (Friedmann et al., 1950). Northern races winter in Mexico and Guatemala.
C. l. borealis (Griscom). Breeds casually in southeastern Arizona (Huachuca Mountains) and in the temperate zone of northern Mexico from 1170 to 3000 meters on both slopes of the Sierra Madre Occidental and the Sierra Madre Oriental, wintering up to 1920 meters from Sonora and Chihuahua to northern Sinaloa and northern Durango. Also reported from Tamaulipas, but birds from this area may be closer to C. l. leucotis (Friedmann et al., 1950).
C. l. leucotis. Resident of southern Mexico from Sinaloa, Durango and San Luis Potosi south to Chiapas.
C. l. borealis (Griscom). Resident of northern Mexico; casual in southern Arizona.
Wing, males 52.5–59.5 mm (ave. of 17, 55.3 mm), females 49–55 mm (ave. of 15, 51.9 mm). Culmen, males 14.5–18.5 mm (ave. of 17, 16.6 mm), females 16–18.5 mm (ave. of 15, 17.4 mm) (Ridgway, 1911). Eggs, ave. 12.5 × 8.0 mm (11.9–12.7 × 7.9–8.3 mm).
Residential ranges of the Xantus (cross-hatched) and white-eared (inked) hummingbirds. The arrowhead represents an extralimital breeding location of the latter. (Adapted from Howell and Webb, 1995)
Breeding females average 3.25 g (Wagner, 1959). The average of 158 males was 3.6 g (SD 0.3 g); that of 51 females was 3.2 g (SD 0.2 g) (Lyon, 1976). A sample of 158 males had a mean mass of 3.6 g (SD 0.30 g); 51 females had mean mass of 3.2 g (SD 0.2 g) (Dunning, 1993).
Adult male. Forehead, loral and malar regions, chin, and upper throat rich metallic violet or violet-blue, passing into velvety black on suborbital and auricular regions and into duller black, faintly glossed with bluish or greenish, on crown; occiput and hindneck dark metallic bronze or bronze-green; back, scapulars, wing-coverts, and rump varying from bright metallic green to bronze-green or golden green; upper tail-coverts similar but usually more bronzy (sometimes golden bronze), and, together with feathers of rump, more or less distinctly margined with rusty; middle pair of rectrices bright bronze-green, bronze, or golden bronze; the next pair similar but darker; the remaining rectrices bronzy black, tipped (more or less distinctly) with bright bronze or bronze-green; remiges purplish dusky, the inner secondaries glossed with bronze-green; a broad white postocular stripe, extending backward and downward above and behind upper margin of auricular region to side of neck; middle and lower throat brilliant metallic emerald green (more yellowish green posteriorly), abruptly defined against the dark violet or violet-blue of upper throat and chin; chest, breast (except medially), sides, and flanks metallic bronze or bronze-green, interrupted by grayish margins to the feathers, the basal grayish also showing where feathers are disarranged; median line of breast and abdomen dull grayish white, sometimes tinged with brownish buffy; femoral tufts dull white; under tail-coverts grayish brown, faintly glossed with bronze, centrally, broadly margined with dull whitish; basal half (more or less) of bill coral red, terminal portion dull blackish; iris dark brown; feet dusky.
Adult female. Above similar to the adult male, but pileum dusky brown, the feathers (especially on forehead) sometimes margined with pale rusty brown, and lateral pair of rectrices broadly tipped with brownish gray; a broad black suborbital and auricular patch and white postocular stripe, as in adult male; underparts pale brownish gray or dull grayish white, spotted with metallic bronze-green, this predominating laterally; median line of breast and abdomen plain dull grayish white or pale brownish gray; under tail-coverts grayish centrally (the shorter ones bronzy or bronze-green) broadly margined with dull grayish white; maxilla dull black, mandible reddish, with terminal portion dusky; iris and feet as in adult male.
Immature male. Pattern of coloration as in adult, but no blue on head, and brilliant emerald-green of throat merely indicated; pileum dull dusky greenish, the feathers margined with dull tawny, this prevailing on occiput; chin and upper throat dull grayish white spotted with dusky; lower throat metallic emerald-green, the feathers distinctly margined with grayish white; prevailing color of rump, superficially, dull tawny, the upper tail-coverts distinctly margined with the same; outer pair of rectrices broadly tipped with light brownish gray, the second pair more narrowly tipped with the same.
Immature female. Like adults, but duller, the feathers of pileum margined with rusty, and spotting of underparts much duller and less metallic.
In the hand. Most likely to be confused with the broad-billed hummingbird, since it too has a reddish base to the bill, which is somewhat broader than deep basally. A long white eye-stripe is present in both sexes, below which a black ear-patch extends forward to the lores. In females this is more dusky, and their throat and underparts are spotted with greenish, rather than uniformly grayish as in females of the broad-billed hummingbird.
In the field. The same criteria as noted above (reddish bill, white eye-stripe, and dark black ear-patch) serve as good fieldmarks, and the females’ greenish tail and greenish flanks and throat are useful in separating this species from females of the otherwise similar broad-billed hummingbird. This species is found in pine-oak woods near streams, and especially in oak woodlands of mountains. Males utter a clear, repeated tink call that sounds like a small bell, delivered constantly from perches.
Little is known of this species’ habitats in the United States, since it is seen only rarely north of the Mexican border. U.S. habitats include woodlands in Cave Creek Canyon of the Chiricahua Mountains and Ramsey Canyon of the Huachuca Mountains in Arizona, the Chisos Mountains of Big Bend National Park in Texas, and the Animas Mountains of New Mexico.
In Mexico the species generally occurs in the temperate zone between 1170 and 3000 meters, nesting at least between 2250 and 3300 meters and wintering up to at least 1900 meters. Schaldach (1963) reported it to be the most abundant breeding bird in open, grassy fields within the arid and humid zones of the pine-oak forests of Colima; and Rowley (1966) also noted that it was the most abundant hummingbird in the upper levels (cloud forest and boreal forest) of his study area in Oaxaca. Moore (1939a) stated that it was the most common hummingbird in the mountains of northwestern Mexico above 1500 meters. It was the dominant species in relation to others of its family there, maintaining control of its preferred food flowers even against larger species such as magnificent and blue-throated hummingbirds. According to Wagner (1959), the species’ altitudinal range is from 1200 to 3900 meters, whereas at the southern end of its range in El Salvador it occurs between 1000 and 2400 meters (Dickey and van Rossem, 1938). In the Soloma region of Guatemala it occurs commonly between 1750 and 2850 meters in scrub oak thickets, pine forests, and along the edges of oak and cloud forests, nesting in adjacent cornfields (Baepler, 1962). More generally in Guatemala it occurs from 1200 to 3300 meters above sea level, preferring the more open woods of oaks, pines, and alders and the clearings and brushy mountainsides (Skutch, in Bent, 1940).
All sorts of scrubby growth, but especially the undergrowth of oak forests, seem to represent optimum habitat for this species. The diverse habitats also include pine woods, rather dense pine-oak forests, high mountain fir forests, partially open mountain country with scattered trees and shrubs, suburban gardens, and even vacant lots with scattered shrubs and flowers.
Texas records of this species extend from April 27 to August 13. Arizona records generally fall between June 9 and August 14 in the Huachuca Mountains, although two specimens were supposedly taken in Arizona on October 1 (Phillips et al., 1964) and one sighting occurred on September 13 (American Birds 25:88). Other than Arizona and Texas, the only other records for the United States are from New Mexico, where the species has been seen a few times in the middle elevations of the Animas Mountains during June and July (Hubbard, 1978).
In the Valley of Mexico, considerable seasonable population variations occur, depending on temperature and rainfall. There, maximum breeding occurs during the summer months from June through September, when both rainfall and insect life also peak. However, elsewhere in Mexico it occurs at other times of the year, such as during spring months in the Colima area and during winter months in the high mountains of Guatemala. Thus, the timing and extent of seasonal movements obviously varies greatly throughout the species’ range (Wagner, 1959).
In the vicinity of Mexico City a proportion of the high montane population migrates, with the weather determining the degree of migration. Although the species is capable of nesting there at any time of the year, during the dry season there is an absence of flexible plant materials needed for nest-building. Thus, there are variations between permanent residents and relatively migratory populations. If there is unusually cold and wet weather between the end of October and the beginning of December, the birds overwinter in the Mexico City area and do not leave for the higher mountain areas for breeding until May or June (Wagner, 1959).
According to Wagner (1959), this species shows no special preference for red flowers. It extracts insects from a variety of flowers, and during the winter also captures insects in flight. In Guatemala, one of the principal food plants at the beginning of the nesting season is a burmarigold (Bidens refracta), which has yellow flowers and produces relatively little nectar. Later, the birds specialize on various species of mints, especially the red-flowered Salvia cinnabarina, but sometimes also the blue-flowered S. cacalioefolia. In Mexico they use the blue-flowered S. mexicana blossoms but avoid the larger and more elongated red flowers of S. cardinalis, which are regularly visited by the larger blue-throated hummingbird (Wagner, 1959).
In an Oaxaca study area, Lyon (1976) found that this species had the most flexible foraging behavior of the six major species of hummingbirds present. It visited a wide range of blossom sizes and exhibited an unusual raiding pattern as well, involving secretive low approaches to stands of Penstemon within the territories of larger and more dominant blue-throated and magnificent hummingbirds. As the average territory sizes of the blue-throats decreased during the summer months, their efficiency of territorial defense increased, thus excluding the white-ears from the Penstemon stands and forcing them to become more dependent on scattered or smaller-flowered species, especially Cuphea jorullensis. The size of male territories in this species averaged 430 square meters, as compared with 720 square meters in the magnificent and 780 square meters in the blue-throated.
In Guatemala, male white-eared hummingbirds become sexually active near the end of the rainy season, just as plants that blossom during the dry season are starting to open. Males gather into “singing assemblies” of as many as seven birds. These groups are well spread out, but probably within hearing distance of one another. The actual distance between individual birds may be from 18 to 30 meters, and the total assemblage may spread out over 180 meters. Some males also display solitarily, well beyond the hearing of all others. Typically the birds sit on exposed perches from less than 1 meter above ground to as much as 12 meters in the air. Each male utters a low, clear tink note that is usually bell-like and repeated endlessly, especially in early morning hours. The seasonal singing activity corresponds to the nesting period of the females; certainly its major purpose is to attract females, but it probably also deters other males from intruding in the territory. Frequently the nearest flowers are at some distance from the singing-perch, and thus the territory serves mainly as a mating station rather than as a means of establishing dominance over a local food resource. In Guatemala these territories are defended for three or four months, from early September until the end of the year (Skutch, in Bent, 1940).
Around Mexico City, the birds sing to some degree during the winter months, but song intensity increases during spring, and by midsummer the males begin to congregate on their common singing grounds. There they call from morning to night in groups of as many as seven individuals, according to Wagner (1959). Only during a short period between late March and late May are the birds sexually inactive in the Mexico City area, but in Colima they apparently breed during that period, which suggests year-round potential for breeding, depending on local conditions.
Courtship involves several stages, beginning with a female’s selection of one individual from the group of males, which she lures to her nesting area. She lands on a tree branch and is immediately courted by the male, which whirs around, above, in front of, and beside her. Sometimes the female moves to a new location, only to be followed by the male; this procedure is repeated several times, with the sitting intervals becoming shorter and the intervening flights longer. While in flight the partners sometimes hover, facing each other, and whenever the female lands, the male repeatedly “invites” her to rejoin him in the air. The ensuing nuptial flight is wild and darting, during which the birds alternate looping maneuvers and short periods of facing each other while hovering. Its final phase is a rapid curving flight during which the birds presumably fly to a mating site.
Nest sites are nearly always in shrubs or fairly low trees. In Guatemala, the usual site is a composite shrub (Baccharis vacinoides) that grows abundantly on the mountainsides. All but 1 of 17 nests found by Skutch (in Bent, 1940) were in bushes of this plant, at heights of 1.5 to 6 meters above ground. However, in Mexico a favored location is on oaks; all 28 nests found by Wagner near Santa Rosa were on oaks (Quercus nitens, less often Q. reticulata), as were 2 of 4 nests described by Moore (1939a) from northwestern Mexico.
Oaks make an attractive nest site probably because the undersides of oak leaves have a downy hairy covering that can be removed, especially where leaf-miner larvae have been active or where leaf galls are present. The nests are constructed mainly out of such materials, which are held down with spider webbing and covered exteriorly with greenish mosses and grayish lichens for camouflage. The nests are usually almost 50 millimeters in diameter, with the rim of the cavity noticeably incurved and about 25 millimeters in diameter; they range from 25 to nearly 75 millimeters in height (Skutch, in Bent, 1940).
From 15 to 20 days are required to build the nest, and 60 to 70 days may elapse from the onset of nest-building to fledging of the young. In the Santa Rosa area of Mexico, resident birds may raise three broods per year (Wagner, 1959). Skutch (in Bent, 1940) suggested that two broods may be raised in a season, and described a female that built a second nest 12 meters away from the first, only a week after fledging the single offspring of her first nesting effort.
Nests of several females are sometimes located fairly close to one another, at times only 35 to 50 meters apart. Further, new nests are often constructed on the foundations of old ones. Incubation lasts from 14 to 16 days, with the longer periods typical of winter months. Likewise, in Mexico the fledging period varies from 23 to 28 days, with the growth of the young dependent on weather and seasonal variations in day-length (Wagner, 1959).
In his report on incubation behavior and nesting development, Skutch (in Bent, 1940) noted that one female devoted nearly eight hours of one day to incubation, and about four hours were spent off the nest, presumably for foraging. By the time the young birds were 7 or 8 days old, their pinfeathers began to sprout, and their eyelids began to part at 9 or 10 days after hatching. Four days later the green portions of their contour feathers appeared, and at 16 days the flight feathers began to emerge from their sheaths. Two days later the tail feathers did the same. The young were brooded nightly until they were 17 or 18 days old, by which time they were well covered with feathers, and in Skutch’s observations fledging required 23 to 26 days. One youngster, 40 days old and two weeks out of the nest, was still fed occasionally by its mother, even though she was now incubating her second clutch of eggs. Wagner (1959) noted that by the time the young are 20 days old they may weigh about 25 percent more than the average adult weight. However, in spite of such maternal care, there is a high incidence of nest and nestling mortality. Skutch (in Bent, 1940) reported that of 18 eggs in 9 nests, only 3 youngsters survived to fledging; Wagner (1959) found that among a total of 39 nests only the nestlings of 12 fledged.
In the judgment of Mayr and Short (1970), this species and the xantus hummingbird of Baja California comprise a superspecies, with the latter a relict form and the most strongly differentiated avian form of that area. I agree with the close relationships of these two species, and I further believe that “Basilinna” and “Cynanthus” should both be considered congeneric with the typical “sapphires” of the genus Hylocharis.
In spite of the wide ecological and geographic range of the species, no hybrids involving the white-eared hummingbird are known. Probably a good part of its success can be attributed to is likely being a generalist forager, using a wide array of blossom sizes and flower heights (Lyon, 1976).