Status and Distribution of Black Vulture in Arizona, with notes on bird finding
Black Vulture, Coragyps atratus, is the most abundant of seven vulture species in the New World (Buckley 1999). It is primarily resident throughout its extensive range; perhaps moving short distances seasonally or during severe weather. In Central and South America, it is widespread and common and is especially abundant around human population centers. Black Vultures frequent fish docks, markets, garbage dumps, and cattle country; otherwise, they inhabit open areas to 2800 m (approximately 9200 ft) rarely venturing into dense, undisturbed forests. Of all the New World vultures, Black Vultures have benefited most from human activity (del Hoyo et al. 1994, AOU 1998).
The northern limits of the Black Vulture’s range is in the United States, where its eastern population is resident from western Texas, eastern Oklahoma, and southern Missouri eastward, north to southern Illinois, southern Indiana, central Ohio, south-central Pennsylvania, and New Jersey. Some portions of the northern and highest elevation populations retreat southward for the winter months; however, throughout the range some individuals remain year-round. For the last several decades, it has been expanding northward where it is currently casual from North Dakota and Wisconsin east to Nova Scotia. (AOU 1998, Buckley 1999)
In the western United States, Black Vultures occur regularly only in Arizona, although, there are accepted records for California and New Mexico (AOU 1998). For Arizona, the most recent in-depth treatments come from Monson and Philips (1981), Rea (1998), and Corman (2005). This manuscript updates the status and distribution for Black Vulture in Arizona since Monson and Phillips (1981) and provides locations where interested observers might find them.
Status and distribution
A relative newcomer to Arizona, the Black Vulture is a sparse and locally uncommon resident along the borderlands of south-central Arizona from Patagonia and Nogales west to Organ Pipe Cactus National Monument. It is regular, sometimes in abundance, north along the Santa Cruz Valley to the confluence of the Santa Cruz and Gila Rivers. This core range has been consistent since at least the mid-1960s (Rea 1983). In recent years, small numbers have begun roosting at the Arizona-Sonora Desert Museum, and showing up at the Avra Valley Wastewater Treatment Facility and elsewhere in the Avra Valley, west of the Tucson Mountains. At Sells, on the Tohono O’odham tribal lands, where it is thought the species reaches its peak abundance, the largest concentrations recorded were >190, 19 Nov 1986 (Stejskal and Witzeman 1987), and another 100
were there 15 November 1997 (Benesh and Rosenberg 1998). At Nogales, 221 were counted during the 2002 Christmas Bird Count, with five other annual counts of >100 individuals (fide J.Bache-Wiig). Other large concentrations (more than 30) were reported from near the Salt and Gila Rivers confluence, Maricopa County; Pinal Airpark pecan grove, Pima County; Red Rock feedlot, Pinal County; and >100 were at Picacho Reservoir, Pinal County, 26 October 2001 (C. Benesh and M. Stevenson, personal communication). After many years of absence, the species returned to the northwestern reaches of its historic range (Phillips et al. 1964) along the confluence of the Salt and Gila Rivers west of Phoenix. It was first noted wandering north on 23 October 1988 (Rosenberg and Stejskal 1989), and by the turn of the century, was a resident along the Gila River from Laveen west to Palo Verde. Corman (2005) suggests nesting as far north as the White Tank Mountains, Maricopa Co. Black Vulture populations in Arizona are stable or slightly increasing.
Unlike the species in Central and South America, Black Vultures in Arizona are not typically found in large cities, preferring instead to remain in the open desert where large mammals, such as free-ranging cattle and horses more often succumb to starvation and thirst (Corman 2005), and roadkills are easier to access. As U.S. cities became more sanitary over the last 80 years, the vultures were decreasingly found living close to humans. They still occur in small rural towns, however, and sometimes nest near humans (Buckley 1999). Corman (2005) found that during the breeding season, Black Vultures in Arizona are most often in desert scrub habitat where there are large saguaros and trees, less often in sparsely vegetated desert areas, and sparingly in small towns, agricultural fields, pecan orchards, riparian woodlands, dense washes, and semiarid grasslands from 300-1200 m (approximately 1000-4000 ft) in elevation. Although the Arizona Breeding Bird Atlas data was collected during the breeding season only, it is likely that these same habitats are used year-round in approximately the same densities. Only six active nests have been reported in Arizona, three in Organ Pipe Cactus National Monument, where they may nest nearly every year at Twin Peaks, and one each at Patagonia, north of the Santa Catalina Mountains, and south of Sonoita (Rea 1998, Corman 2005, T. Tibbitts, personal communication).
There is little movement outside the immediate vicinity of the species’ known range. During fall and winter, Black Vultures often amass in large, roosting flocks; however, Philips et al. (1964) hypothesize these concentrations are the product of the most favorable feeding grounds attracting birds from a wider area of residency, not from a seasonal movement. Considering how high Black Vultures soar and how this allows them to travel great distances quickly, it is remarkable that we do not see many far-flung vagrants. There continues to be no accepted records within the lower Colorado River Valley. The California Bird Records Committee did not accept the single report from the California side of the Colorado River near Parker Dam (Rosenberg et al. 1991). There is a recent history of individuals wandering north to Chandler and Queen Creek, but this is within the historic range. Other wandering individuals were at the confluence of the Salt and Verde Rivers 14 May 2005 (fide T. Corman), south of Sierra Vista 9 August 1989 (Rosenberg and Stejskal 1990), and at the San Bernardino National Wildlife Refuge, Cochise County, east of Douglas, 26 April 2005 (R. Webster, personal communication). Although, Monson and Philips (1981) comment that the species is present at the latter location February July, this is the only record I could find, with another individual at Douglas 30 May 1984 (Stejskal and Witzeman 1984).
Black Vultures are very opportunistic, with ephemeral food sources, sometimes directly associated with humans, likely playing a role in range expansion. A primitive slaughterhouse along the Gila River was one of the first locations where the species was found during the 1990s west of Phoenix, and another on the outskirts of Tucson attracted birds in the early years (Phillips et al. 1964).
Where to find Black Vultures
The best places to find Black Vultures are Patagonia and Nogales in the southeast, along the Santa Cruz River north of Tucson, and for those not venturing to the southeast part of the state, the areas west of Phoenix along the Gila and Salt Rivers. At Patagonia, look for the vultures at the Roadside Rest and at the Patagonia Sonoita Creek Sanctuary. Kettles of Black Vultures are often seen just north of Nogales in the flat agricultural areas along the Santa Cruz River. Also look for them in the areas surrounding the Nogales Wastewater Treatment Facility (to date the facility itself remains closed to the public). North of Tucson, check for roosting birds at the Pinal Airpark pecan grove or near the feedlot in Red Rock, and when water is present, Picacho Reservoir also supports sizable numbers. In Phoenix, watch for soaring birds over dairy farms and agricultural areas, as well as perched on the high-tension transmission towers just north of Phoenix International Raceway and the Gila River.
Thanks to Troy Corman, Doug Jenness, Jill Jones, and Kurt Radamaker for providing comments on drafts of this paper. Steve Ganley and Mark Stevenson provided additional records; Tim Tibbitts added information from Organ Pipe Cactus National Monument; and Troy Corman provided an advance copy of his species account from the forthcoming Arizona Breeding Bird Atlas.
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