California Partners in Flight Desert Bird Conservation Plan
Ash-throated Flycatcher (Myiarchus cinerascens)
http://kaweahoaks.com/html/ash_throated_flycatcher.html (need permission to publish)
Prepared by: Ryan Carle (firstname.lastname@example.org) and Debra L. Hughson (email@example.com)
Mojave National Preserve
2701 Barstow Road, Barstow CA 92311
Carle, R. and Hughson, D. 2008. Ash-throated Flycatcher (Myiarchus cinarascens). In The Desert Bird Conservation Plan. California Partners in Flight.
action plan summary
Two subspecies identified: Myiarchus cinerascens cinerascens, which breeds through much of the southwestern United States and the Mexican plateau, and Myiarchus cinerascens pertinax in Baja California (NODC Taxonomic Code, database (version 8.0) 1996)
Presently not listed in California as a Species of Special Concern, a Fully Protected Species, or a Threatened and Endangered Species.
CURRENT BREEDING DISTRIBUTION:
Breeds throughout western United States in appropriate habitats. Ranges from eastern Washington state south to Mexico and west to Western Texas and Oklahoma. In Mexico, breeds in Baja California and throughout North-Central Mexico with extreme edge of range in Guanajuato (Cardiff and Dittmann 2002).
In the California deserts Ash-throated Flycatchers nest primarily in cottonwood-willow riparian, mesquite woodland, Joshua tree/yucca, and xeric-riparian woodland. Nesting has been confirmed in Amargosa Canyon, Piute Spring, and along the Lower Colorado River corridor at Havasu, Chemehuevi Wash, and the Whipple Mountains (McCreedy, in prep). Nesting is commonly observed in the Owens Valley, watersheds of the Western Sierra Nevada, the Central Valley, the San Francisco Bay Area, and other parts of northern California outside the scope of this report (Cardiff and Dittmann 2002).
Figure 1: Breeding Bird Survey (BBS) summer distribution map of Ash-throated Flycatcher in the US. This survey is typically performed in June by volunteers on over 4000 bird counts. The counts are done by vehicle during the morning. (http://www.mbr-pwrc.usgs.gov/id/framlst/i4540id.html).
Winters primarily south of the U.S. from Mexico (Williams 1993) to Costa Rica, although has been observed to winter as far north as southern Nevada. Small numbers (estimated 3% of local summer population) overwinter in the Lower Colorado River Valley (Rosenberg et al. 1991).
No large scale changes in distribution are known. Local expansions have occurred in previously treeless areas where artificial nesting sites have been introduced (e.g. nest boxes and metal poles). Substantial amounts of historic habitat have undoubtedly been lost due to clearing of land for development and changes in historic fire and flooding regimes (Cardiff and Dittmann 2002).
AVERAGE TERRITORY SIZE:
Verner and Boss (1980) report territories ranging from 3.0 ha in desert wash habitat to 10 ha in open desert. Density estimates in desert habitat range up to 0.8 pairs per 40 ha (Emlen 1974).
TIME AND OCCURENCE OF SEASONAL MOVEMENTS:
Ash-throated Flycatchers arrive in breeding areas of Southern California as early as March and breeding can begin as early as mid-March (Rosenberg et al. 1991). The main breeding season is May and June. Migration south begins after breeding by late July to early August (Cardiff and Dittmann 2002).
Sallies from perch in lower branches of trees or tops of shrubs to catch prey in low foliage or on ground, usually returning to a different perch. Seldom hawks insects in midair. Will sometimes glean prey such as mites, worms, and insects from the ground and tree bark. Tenderizes larger prey by repeatedly striking against a branch while holding in bill (Cardiff and Dittman 2002).
Diet consists primarily of insects and spiders. Feeds on small fruits and berries in season. Has been documented to take small reptiles and mammals (Rosenberg et al. 1991, Johnson 1982).
Little studied. Lives in a wide variety of arid habitats and presumably obtains moisture from diet. Ash-throated Flycatchers apparently do not drink water even when it is readily available. (Smyth and Coulombe 1971, Cardiff and Dittman 2002).
Desert populations inhabit cottonwood-willow riparian, mesquite woodland, xeric-riparian woodland, uplands of columnar cacti, and Joshua tree woodland. Outside of desert found in oak woodland and pinyon-juniper habitats (USDA 1991) below about 1400 m. Breeding habitat determined partly by availability of cavities (Brush 1981, Rosenberg et al. 1991).
Secondary cavity nester. Utilizes natural cavities: hollow stumps, abandoned woodpecker holes, stems of yucca and agave, and old cactus wren nests (Harrison 1978). Readily nests in a wide variety of artificial structures such as nest boxes, metal posts, old cans, and mailboxes. (Dunning and Bowers 1990, Rosenberg, et al 1991, Purcell et al. 1997). Occasionally usurps cavities from woodpeckers and small cavity nesters such as tufted titmouse (Baeolophus bicolor) and Bewick’s wren (Thryomanes bewickii) (Cardiff and Dittmann 2002).
DOMINANT CANOPY SPECIES:
Nests in a wide variety of plant substrates with cavities. In desert riparian zones, willows (Salix spp.) and Fremont cottonwood (Populus fremontii). In xeric-riparian woodland, blue palo verde (Cercidium floridum), ironwood (Olneya tesota) (McCreedy, in prep) and honey mesquite (Prosopis glandulosa) (Rosenberg et al. 1991). In saguaro scrub, giant saguaro (Carnegia gigantea), organ pipe cactus (Stenocereus thurberi) and cardón (Pachycereus pringlei). In Mojave, Joshua tree (Yucca brevifolia) and yuccas (Yucca spp.). In Great Basin, pinyon pine (Pinus monophylla) and Utah juniper (Juniperus osteosperma) (Cardiff and Dittmann 2002).
DOMINANT SHRUB SPECIES:
Utilizes a wide variety of low shrubs for perching and foraging (Grinnell and Miller 1944). In desert washes, important foraging shrubs are honey mesquite, saltbush (Atroplex), and wolfberry (Lycium)(Rosenberg, et al. 1991). Prefers relatively open, arid shrublands (Cardiff and Dittmann 2002).
DOMINANT FORB SPECIES:
Not applicable. Primarily limited by nesting and perching sites rather than forb cover (Brush 1981).
HEIGHT OF NEST:
Nest height averages 1 to 6 m above ground level, usually greater than .3 m above ground (Cardiff and Dittmann 2002).
Uses cavities in live or dead trees. Female builds a cup of fine roots, grass, plant stems, and dried manure and lines it with fine grasses and matted hair and fur (Harrison 1978).
Ash-throated Flycatchers are normally monogamous (Verner and Willson 1969). Breeding displays are not well-described. Male closely follows female during nest-building. The pair aggressively defends the nest against conspecifics and other species. (Cardiff and Dittmann 2002).
Clutch size can range from 3 to 7 eggs but is usually 4 to 5 eggs (Harrison 1978).
Female (Harrison 1978)
The incubation period is 14-16 days by the female, who may leave the nest for hours at a time during the hot part of the day (Bent 1942).
DEVELOPMENT AT HATCHING:
Altricial (Harrison 1978).
16-17 days. After fledging, young may become independent in as little as three days (Bent 1942) or continue to be fed by parents for up two another two weeks (Cardiff and Dittmann 2002).
Both sexes tend young (Harrison 1978).
NUMBER OF BROODS:
Single brood in northerly latitudes and at high elevations where breeders arrive later in Spring (mid-April –May). Usually raises two broods in the Lower Colorado River Valley, where it is possible to start breeding much earlier (March-mid-April). (Rosenburg, et al. 1991, Cardiff and Dittmann 2002)
Desert populations of Ash-throated Flycatcher occupy low (100 – 1700 m) shrublands, ranging up to 2300 m in pinyon-juniper woodland.
A study of anthropogenic fragmentation and livestock grazing in western riparian bird communities did not report significant effects to Ash-throated Flycatchers (Tewksbury et al. 2002). In suburban areas dominated by non-native vegetation, Ash-throated Flycatcher densities tend to be significantly lower than in unfragmented habitats (Cardiff and Dittmann 2002). Densities may increase in suburban environments if native plants and suitable nesting sites are incorporated into landscaping (Emlen 1974, Cardiff and Dittmann 2002).
Large areas of historic riparian nesting grounds in the Southwest have been degraded by the invasion of salt cedar (Tamarix). Ash-throated Flycatchers make virtually no use of salt cedar habitats, possibly because salt cedar does not provide adequate cavities for nesting. (Rosenberg et al 1991).
It is possible that creation of artificial nesting sites could somewhat offset habitat loss. Brush (1981) found that though densities could be inflated by installing nest boxes, many suitable cavities always remained vacant. Large feeding territories (3-4 ha) also appear to be vital (Rosenberg et al 1991).
Invasions of exotic annual grasses have radically altered the historic fire regimes of the Sonoran and Mojave deserts in recent years (McCreedy 2008). This has caused dramatically increased frequency and intensity of fires in a system previously dominated by flood disturbance rather than fire (Smith et al. 2007). While the burning of desert riparian vegetation has negative effects on many bird species, Ash-throated Flycatchers may actually benefit. Smith et al. (2007) found that Ash-throated Flycatchers responded positively in recently burned desert riparian habitats, possibly because of increased cavity availability and abundant food from fire-induced insect hatches. Response to fire in California oak woodland was also positive (Purcell and Stephens 2005). There has not been sufficient study to determine whether fire might be beneficial or detrimental throughout its entire range. Smith, et al. note that proper post-fire management (such as leaving burnt snags standing) is an important factor if fires are to improve habitat.
Flooding: Flood control projects have resulted in large-scale loss of habitat (Cardiff and Dittmann 2002). Poor hydrological management on the Colorado River has resulted in the loss of cottonwood-willow habitat from prolonged flooding (Rosenberg et al 1991).
Grazing: Abundance of Ash-throated Flycatchers was found to be significantly higher, by a factor of 7, inside the Desert Tortoise Natural Area than outside (Brooks 1999), likely due to protection from livestock grazing and off-highway vehicle use. Adjacent Land Use: Little information. Fair et al (2003) found that nesting was more successful farther away from soil contamination sources. As previously noted, Ash-throated Flycatchers can potentially increase densities in suburban areas with native vegetation.
Secondary poisoning of adults can occur from ants contaminated with Sodium Monofluoroacetate 1080 (Hegdal et al. 1986). Proximity to soil contaminants, including heavy metals, chemicals, insecticides, polychlorinated biphenyls, and radioactive isotopes has been spatially correlated (within 60m) to lowered nestling survivorship (Fair et al. 2003).
Redman (2003) found predation to be the most common cause of nest failure in the Mojave Desert but was unable to identify the predator. At least three species of rodents and 7 species of birds were found to prey on cavity-nesting birds in the San Joaquin Experimental Range. Avian predators include western scrub-jay (Aphelocoma californica), pinyon jay (Gymnorhinus cyanocephalus), and common raven (Corvus corax) (Purcell and Verner 1999).
DEMOGRAPHY AND POPULATION TRENDS:
AGE AND SEX RATIOS:
Redman (2003) observed total nesting failure at 29 nests in 2001 and 2002, which he attributed to drought and predation. Institute for Bird Populations (http://www.birdpop.org/) data show reproductive indexes (ratio of number of juveniles to number of adults) ranging between zero and 0.185 in the southwest over the period from 1992 to 2001 with an average of 0.092.
Annual probability of adult survival in the southwest for the 1992 to 2001 period was 0.659 (http://www.birdpop.org/) based on a total of 787 captures and 676 individuals.
Little information. Banding studies of a resident population in Sonora, Mexico indicated that some individuals may remain and breed in areas near where they hatched (Russell and Monson 1998).
Trends in number of adults, based on Monitoring Avian Productivity and Survivorship (MAPS) Program data, were negative in the southwest region for all years from 1995 through 2000. Only 2001 showed a positive trend, possibly indicating a gradual regional decline.
Figure 2. Ash-throated Flycatcher population trend, 1966-2003
EXOTIC SPECIES INVASION/ENCROACHMENT:
Large areas of historic riparian nesting grounds in the Southwest have been degraded by the invasion of salt cedar (Tamarix). Ash-throated Flycatchers make virtually no use of salt cedar habitats, possibly because salt cedar does not provide adequate cavities for nesting. (Rosenberg et al. 1991). In a study (Brush 1981) in which nest boxes were placed in salt cedar habitats in the Lower Colorado River Valley, no cavity nesting birds utilized the boxes, indicating that salt cedar may be inadequate habitat regardless of the presence of nest sites. Large scale salt cedar removal and cottonwood plantation projects in the Lower Colorado River Valley are underway that may provide superior habitat for Ash-throated Flycatchers in the future (McCreedy 2008, Rosenberg et al, 1991.)
Invasions of exotic annual grasses have altered desert fire regimes, but it is possible that these changes could benefit Ash-throated Flycatchers, especially with proper post-fire management to retain habitat (see FIRE section above).
Ash-throated Flycatchers are partially dependent on woodpeckers for the creation of cavity nesting sites (Cardiff and Dittmann 2002). Conservation of Gila and ladder-backed woodpeckers and gilded and northern flickers would benefit desert populations of Ash-throated Flycatcher. Conservation of desert riparian, mesquite woodland, and xeric- riparian woodland habitat would benefit a great many desert bird species. Secondary cavity nesters such as brown-crested flycatchers, dusky-capped flycatchers, American kestrels, ferruginous pygmy-owls, elf owls, western screech-owls, and Lucy’s warblers would benefit from protection of Ash-throated Flycatcher nesting habitats.
Protection of the Ash-throated Flycatcher’s Central American wintering grounds would undoubtedly benefit a great many other neo-tropical migrants.
ACTION PLAN SUMMARY
Presently not listed in California as a Species of Special Concern, a Fully Protected Species, or a Threatened and Endangered Species.
Primary habitat need is suitable nesting sites (Brush 1981). Important plant communities are cottonwood-willow riparian, mesquite woodland, xeric-riparian woodland, and Joshua tree/yucca habitats (Rosenberg et al. 1991, Cardiff and Dittmann 2002). Important nesting substrates are Fremont cottonwood (Populus fremontii), willow (Salix spp.), honey mesquite (Prosopsis glandulosa) saguaro (Cereus giganteus), blue palo verde (Cercidium floridum), Joshua tree (Yucca brevifolia) and yucca (Yucca spp). Important foraging shrubs include honey mesquite (Prosopis glandulosa), fourwing saltbush (Atriplex canescens), and wolfberry (Lycium) (Rosenberg et al. 1991). Readily nests in human-created cavities, but benefits in suburban habitats from presence of native plant species (Emlen 1974).
Requires large territories for breeding and feeding (greater than 3-4 ha) (Rosenberg et al. 1991).
The rapid growth of human population in the Sonoran and Mojave deserts and the associated large-scale changes in land use, invasion of exotic species, and changes in disturbance regimes threaten all native bird species. The great adaptability of Ash-throated Flycatchers is certainly an advantage, but does not ensure future survival.
Habitat loss and degradation pose the most serious threat, and protection and restoration of riparian corridors and desert washes should be a primary objective. Including native vegetation and nest boxes in suburban and urban areas would help offset habitat loss from human development (Emlen 1972, Cardiff and Dittmann 2002). Other beneficial measures would be post-fire management that maintains nesting sites (Smith et al. 2007), salt cedar removal, reduction of riparian grazing, cottonwood plantations, and restoration of hydrological functions. Pesticides and other pollution pose a threat (Fair 2003) and need further study.
Conservation of cavity-creating woodpecker species such as the Gila woodpecker would directly benefit Ash-throated Flycatchers. There is some concern that European starling competition for nest cavities may be causing the decline of Gila woodpeckers (Kerpez and Smith 1990a, McCreedy 2008). Starling control could prove an important indirect measure for Ash-throated Flycatcher conservation.
Wintering range is poorly understood and needs further study and conservation (Cardiff and Dittmann 2002). Of primary importance is protecting and studying remaining intact breeding habitats.
MONITORING METHODS AND RESEARCH NEEDS:
Large (greater than 40 ha) study plots are required for monitoring nesting behavior and success of Ash-throated Flycatchers due to typically low densities (Redman 2003).
Very little demographic information exists and studies on reproductive success and survivorship are needed. Further research on responses to fire, soil contaminants, salt cedar, suburbanization, and grazing would be beneficial. Little is understood about natural history, threats, and conservation priorities on migration routes and wintering grounds. Further study of breeding biology and specific breeding locations within range, especially in Mexico, would help further understanding of conservation needs.
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