Residential range of the plain-capped starthroat. (Adapted from Howell and Webb, 1995)
Constant star-throat; Chupamirto ocotero, Chupaflor pochotero (Spanish).
Breeds in the arid tropical zone of the Pacific Coast from southern Sonora, Mexico, south to Costa Rica (Friedmann et al., 1950). Accidental in Arizona.
H. c. pinicola (Gould). Confined to the western slope of the Sierra Madre Occidental, from sea level to about 1200 meters, from extreme southern Sonora to western Jalisco (Friedmann et al., 1950).
H. c. leocadiae (Bourcier and Mulsant). Resident of central and southwestern Mexico, from Michoacan and Guerrero south to Guatemala.
Wing, males 63–70.5 mm (ave. of 15, 66.9 mm), females 64–68.5 mm (ave. of 10, 65.7 mm). Culmen, males 33.5–36.5 mm (ave. of 15, 34.5 mm), females 34–37.5 mm (ave. of 10, 35.5 mm) (Ridgway, 1911). Eggs, apparently undescribed. Those of the slightly smaller H. longirostris average 13.2 × 8.65 mm (Rowley, 1966).
The average weight of 6 males was 7.43 g (range 6.5–9.0); that of 3 females was 7.2 g (range 6.8–7.8 g) (J. L. Des Granges, personal communication). A sample of live-captured and museum specimens (sex and number unstated) averaged 7.5 g (SD 0.9 g) (Arizmendi and Ornelas, 1990).
Adult male. Above metallic bronze or bronze-green, somewhat duller on pileum, especially on forehead; rump with longitudinal median patch or broad streak of white; middle rectrices usually dusky terminally, the other retrices extensively blackish terminally, the inner web tipped with a spot of white; remiges brownish slate or dusky, faintly glossed with purplish; a postocular spot and a conspicuous malar stripe dull white; the auricular, suborbital, and loral regions dusky; chin sooty or blackish; throat bright metallic red or purplish red (varying from orange-red or scarlet to rose-red), the feathers narrowly margined terminally with pale grayish or dull whitish (invisible except when viewed from behind); underparts of body brownish gray (deep smoke gray or nearly mouse gray), fading to white on abdomen and anal and femoral regions; under tail-coverts pale gray basally, dusky subterminally (in form of a V- or U-shaped bar), broadly white terminally; a large and conspicuous tuft of silky white feathers on sides, between flanks and back; bill dull black; iris dark brown; feet dusky.
Residential range of the plain-capped starthroat. (Adapted from Howell and Webb, 1995)
Adult female. Very similar to the adult male and not always distinguishable, but usually (?) with the blackish of chin slightly more extended.
Immature. Similar to adults, but greater part (sometimes whole) of throat dark sooty brown or dusky, the feathers margined terminally with grayish white.
In the hand. Very large size (wing more than 60 mm) and long bill (culmen 33–38 mm) eliminate all other North American species; moreover, the tail feathers are broadly tipped with white.
In the field. Associated with arid scrubby lowlands, woodland borders, dry woods, plantations, and the like. Its very large size, long bill, and broadly white-tipped tail are distinctive. There is also a streak of white on the rump, a white malar stripe, and a throat that is sometimes glittering red (males) or spotted with dusky (females). Both sexes have dark grayish underparts. These birds often hawk for insects. While they are in flight, and sometimes while perched, a tuft of white flank feathers may be visible near the posterior edge of the wing.
In Mexico this species occurs in scrubby, rather arid woodlands, woodland edges, partially open country with scattered trees or thickets, and scrubby riparian woodland, from sea level to 1500 meters (Edwards, 1973). In Colima it is found from the thorn forest zone to the upper edges of the tropical deciduous forest, but is most common in the denser thorn forest zone (Schaldach, 1963).
Since the plain-capped starthroat is essentially tropical in distribution, it probably undergoes relatively few seasonal movements. In Sonora it is essentially a resident species, but van Rossem (1945) suggested that there may be a partial exodus from there during the winter months.
Post-breeding wandering has perhaps accounted for the few records of this species in the United States, most of which have occurred in Arizona. The first reported individual visited a feeder in Nogales during late September 1969. In 1978 an individual was seen at a feeder in Patagonia, Arizona, between July 15 and 20. Earlier that year a possible sighting of the species was made on June 17 in Sycamore Canyon, west of Nogales, and on June 24 a similar sighting was made southwest of Patagonia. These sightings all occurred close to the Mexican border, about 500 kilometers north of the species’ known range limits in Sonora. Finally, in Phoenix, well to the north of these observations, an individual frequented a yard feeder from October 17 to November 28, 1978 (Witzeman, 1979), and on June 28, 1980, an individual was observed near Sierra Vista (American Birds 34:919). There are also two recent New Mexico sight records (American Birds 48:138).
Almost nothing is known of the foraging ecology of the plain-capped starthroat. According to Des Granges (1979), it resides in the Volcan de Colima area and has exhibited feeding territoriality there. It showed a moderate degree of social dominance with other species, but almost throughout the entire year it fed nearly exclusively on aerial arthropods; during the short blooming period of Ceiba aesculifolia, however, nectar-feeding occupied nearly all of its time. This species frequently catches insects while flying close to the ground above roads or wide trails, and otherwise tends to perch quietly 4 to 6 meters above ground (Edwards, 1973).
There is apparently no description available of the nest or breeding activities of this species.
The two Central American species of starthroats are so similar to each other that they may constitute a superspecies, with the plain-capped starthroat occupying more arid and westerly portions of Mexico and Central America and the long-billed starthroat adapted to more humid lowlands, extending southward to Brazil.
The unusually long and decurved bills of the starthroats approach those of the hermit hummingbirds, and perhaps these species compete locally to some extent. However, at least the plain-capped starthroat is strongly insectivorous and does not normally defend feeding territories (Des Granges, 1979).