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Vaux's Swift
Chaetura vauxi
NatureServe conservation status
Global (G-rank): G5
State (S-rank): SNA
External links
Species range
BREEDING: southeastern Alaska, southern British Columbia, northern Idaho, and western Montana south to central California (migratory populations); also southwestern Tamaulipas and southeastern San Luis Potosi, Yucatan Peninsula, western Mexico south to Panama, and in northern Venezuela (resident populations) (AOU 1983, Bull and Collins 1993, Rappole 1995). NON-BREEDING: central Mexico south through breeding range in Middle America and Venezuela; casual in California, southern Louisiana, and western Florida (AOU 1983, Bull and Collins 1993).
Migration
Breeding populations in U.S. and Canada make long migrations to Mexico, Central America and Venezuela (Bull and Collins 1993). A few winter irregularly in southern coastal lowlands of California (CDFG 2000). Resident throughout the year in Mexico, Central America, and Venezuela but may make local migrations to lowlands (Stiles and Skutch 1989; Howell and Webb 1995). In Oregon, some left their nesting areas in late August and early September and were found at large communal roosts sheltering more than 500 swifts; these large roosts were used until mid-September when swifts left the study area (Bull and Blumton 1997).
Habitat
Found in mature forests but also forages and migrates over open country (Tropical to Temperate zone) (AOU 1983; Bull and Collins 1993). Forages over land and water. Often roosts in large flocks in hollow trees or chimneys just prior to and during migration (Bull and Blumton 1997, Eshbaugh 2000). BREEDING: In North America, prefers late seral stages of coniferous and mixed deciduous/coniferous forests; more abundant in old-growth forests than in younger stands (Manuwal and Huff 1987, Gilbert and Allwine 1991, Huff and Raley 1991, Lundquist and Mariani 1991; Manuwal 1991; Bull and Collins 1993). In Washington, found more abundant in old-growth (> 250 years old) than in younger (< 165 years old) forest stands (Manuwal and Huff 1987), and more abundant in wet old-growth than mesic or dry old-growth (Manuwal 1991). In the southern Washington Cascade Mountains, abundance was positively correlated with high density of live trees >100 cm in diameter at breast height (mainly Douglas-fir [PSEUDOTSUGA MENZIESII], Western Hemlock [TSUGA HETEROPHYLLA], and Western Redcedar [THUJA PLICATA]) and with large snags (Douglas-fir and Western Hemlock; Lundquist and Mariani 1991). The multi-layered broken overstory of old-growth forests may also provide easier access to aerial insects than closed, continuous canopies of younger forests (Lundquist and Mariani 1991). In northern California, uses Douglas-fir forests but highest densities are in coastal redwood (SEQUOIA SEMPERVIRENS) habitats (Sterling and Paton 1996; CDFG 2000). BREEDING AND WINTERING: In the neotropics, found in mixed coniferous-broadleaf, deciduous broadleaf, and broadleaf evergreen forests (Rappole et al. 1995). In Mexico, breeds in highlands, ranging into lowlands in migration or winter; although a disjunct population is resident on the Yucatan Peninsula (Howell and Webb 1995). In Honduras, common in humid Caribbean lowlands to interior highlands up to 2000m; one breeding record in cloud forest; flock also recorded feeding around a large almendro tree (DIPTERYX OLEIFERA) in an open field (Monroe 1968). In Costa Rica, resident in highlands (700-2000 m), occasionally ranging higher or into lowlands (Stiles and Skutch 1989). NEST SITES: Nests are usually in large-diameter hollow trees, broken-top trees, or stumps; also in chimneys. Nest is a saucer-shaped structure of twigs and spruce or pine needles glued to interior vertical wall of hollow tree, stump, chimney, dark attic, or similar dark cranny. Usually locates nest near bottom of cavity (Baicich and Harrison 1997; Bull and Collins 1993). In Oregon, nests have been recorded in live or dead Grand Fir (ABIES GRANDIS) and Bigleaf Maple (ACER MACROPHYLLUM) with hollow chambers where heartwood had decayed (Bull and Cooper 1991; Bull and Collins 1993). For 21 nests located in a northeastern Oregon study, nest trees averaged 67.5 cm diameter at breast height (range 45-96 cm) and 25 m tall (range 15-37 m), and usually occurred in old-growth forest with an average canopy closure of 71%. All of these nests were in trees hollowed out by Indian paint fungus (ECHINODONTIUM TINCTORUM) and with an entrance hole excavated by Pileated Woodpeckers (Bull and Cooper 1991). In Washington, one nest recorded in a broken-topped Western Redcedar (THUJA PLICATA) 10 m tall and 76 cm diameter at breast height in old-growth forest (Lundquist and Mariani 1991). In Montana, three nests recorded in old broken-topped Western Hemlock (TSUGA HETEROPHYLLA; Baldwin and Zaczkowski 1963). Less typical records in cottonwood (POPULUS spp.) and sycamore (Platanus spp.; Taylor 1905). In British Columbia, the only confirmed tree nest was in a hollow Bigleaf Maple; there are several other records of birds seen entering or leaving Western Redcedars and Black Cottonwoods (POPULUS TRICHOCARPA), but nesting was not confirmed (Campbell et al. 1990, M. G. Shepard, pers. comm.). ROOSTS: Two roosts were recorded in northeastern Oregon, both in Grand Fir trees 200-300 years old, > 100 cm diameter at breast height in old-growth forest stands (Bull 1991). Postfledging swifts in Oregon roosted in the nest tree (44% of juveniles, 64% of adults) or in trees up to 9.2 kilometers away. Roost trees were hollow, live or dead grand firs (94%) or ponderosa pines (6%), with an average DBH of 77 cm and an average height of 26 m (Bull and Blumton 1997). One record of birds roosting in the open: in southern California a large tight cluster was found on the trunk of a tamarisk tree (TAMARIX spp.; Stager 1965). In Oregon, the largest migratory roost (15,000 to 40,000 birds) is in a large brick chimney at a school in Portland (Eshbaugh 2000).
Food habits
Feeds on small flying insects; catches insects in the air. Feeds in long, continuous foraging flights high over varied habitats; also at lower levels over forest openings, burns, rivers and lakes (Grinnell and Miller 1944). In Oregon, foraged up to 5.4 km from the nest but mostly near the nest stand (Bull and Beckwith 1993). Often joins other swifts in feeding at edges of rainstorms (Stiles and Skutch 1989; Campbell et al. 1990). Feeds on leafhoppers, true flies; see Bull and Beckwith (1993) for extensive information on diet in Oregon.
Ecology
Forages and migrates during day. May enter torpor in periods of cold weather (Terres 1980). Number of birds at two tree roosts monitored in northeastern Oregon ranged from 9 to 479, with highest counts in spring (Bull 1991). During migration can gather in very large roosting flocks; up to 40,000 regularly roost in one large chimney in Portland (Eshbaugh 2000), and other large chimney roosts occur in a variety of Oregon cities (Bull 2000) and in Los Angeles, California.
Reproductive characteristics
Nests singly or in small colony. Clutch size is 3-7 (usually 4-7). Incubation lasts 18-20 days (Stiles and Skutch 1989; Baicich and Harrison 1997). Young leave nest after 20-21 days; will perch on interior wall the nest is built on, but may not fly freely for up to another 7 days (Baldwin and Zaczkowski 1963). At least some birds nest at one year of age (Bull and Collins 1996). Will return to same nest site (Baldwin and Zaczkowski 1963; Bull and Collins 1996). In an Oregon study, 70% of 46 nest trees were re-used in subsequent years, and nest site fidelity was also high, with 14 of 15 marked birds recaptured at the same nest tree (Bull and Collins 1996).
Threats or limiting factors
Logging of older trees and hollow snags eliminates nest and roost habitat. "Forest health" management activities that reduce incidence of heartrot and aerial insects would also reduce potential habitat and prey. Factors that reduce abundance of Pileated Woodpeckers may in turn reduce cavity availability and impact swifts. Logging reduced old-growth habitats in the Pacific Northwest (Bull and Beckwith 1993). In California, where the species occurs in greatest abundance in coastal redwood forests, less than 10% of the original old-growth redwood forests remain (Sterling and Paton 1996). To a much lesser extent, swifts may be losing nesting possibilities where brick chimneys are replaced with insulated pipe or covered with screen spark-arresters (Bull and Collins 1993). Large migratory roosts in chimneys may be lost when chimneys are covered or replaced, or birds may even be killed by inadvertent use of the chimneys' furnaces, etc. (Eshbaugh 2000). Activities such as pesticide spraying that impact aerial insects could decrease food availability, but no data available.
