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Federal Register / Vol. 86, No. 55 / Wednesday, March 24, 2021 / Rules and Regulations
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area west of the Rocky Mountains, with most observations occurring from the Cascade Mountains and Sierra Nevada to the coast Snyder and Snyder 2000, p. 12; DElia and Haig 2013, pp. 3859.
California condor population declines and range contractions were concurrent with Euro-American settlement of the West, with condors disappearing from the Pacific Northwest in the early 1900s DElia and Haig 2013, pp. 5859, and from Baja California by the end of the 1930s Wilbur and Kiff 1980, entire. By the middle of the 20th century, the species was reduced to about 150
individuals limited to the mountains of southern California Snyder and Snyder 2000, pp. 8182, and at the time we formally classified them as an endangered species in 1967, the population had further declined to an estimated 60 condors Snyder and Snyder 2000, pp. 8283. Most probable causes of their historical decline include: 1 Secondary poisoning from predator removal campaigns, 2 direct persecution, and 3 lead poisoning from spent ammunition that fragmented in animals condors later fed upon DElia and Haig 2013, pp. 77122.
Captive Breeding, Reintroduction Efforts, and Current Range Due to concerns over the few remaining California condors and the populations continued downward trend, beginning in 1983, we took all condor eggs from the wild to the San Diego Wild Animal Park and Los Angeles Zoo for artificial incubation to form a captive flock Snyder and Hamber 1985, p. 378; Snyder and Snyder 2000, pp. 278293. By taking all wild eggs and inducing multiple clutches and annual nesting, the productivity of the population was increased several-fold, allowing the captive population to grow rapidly Snyder and Hamber 1985, p. 378.
However, with the sudden loss of several wild California condors in 1984
and 1985, it became necessary for us to capture the remaining wild individuals to ensure the genetic viability of the species and enhance the chances of the captive-breeding programs success Snyder and Snyder 2000, pp. 298304.
By 1987, the California condor existed only in captivity, having suffered a severe population bottleneck and loss of genetic diversity Ralls and Ballou 2004, p. 225; DElia et al. 2016, pp. 707708.
Thus, the conservation of the species was dependent upon captive breeding and releases back into the wild.
We first released captive-reared California condors in 1992 in southern California, but because of behavioral problems exhibited by these individuals
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we returned them all to captivity in early 1995 Snyder and Snyder 2000, pp. 344345. We reinitiated releases of captive-reared and formerly wild California condors in southern California in 1995, and additional release sites were established in northern Arizona in 1996, central California near Big Sur in 1997, Sierra de San Pedro Martir in Baja California, Mexico, in 2002, Pinnacles National Park formerly Pinnacles National Monument in 2003, and in the mountains near San Simeon, California, in 2015. Currently, these release sites comprise four general release areas central California, southern California, Baja California, and Arizona/Utah in three condor populations a population in central and southern California where individuals from each release area occasionally intermingleand independent populations in northern Arizona/southern Utah and Baja California. The California condor is currently absent from the northern portion of its historical range and remains reliant on the release of captivebred individuals for population growth USFWS 2013, p. 14.
As of December 2019, there were 337
California condors in the wild, divided among the four release areas: Central and southern California 200 condors;
northern Arizona and southern Utah 98
condors; and the Sierra de San Pedro Martir release site in Baja California 39
condors USFWS 2019a, p. 1. There were also 181 California condors in captivity USFWS 2019a, p. 1
distributed among release sites, zoos, and four captive-breeding facilities in the United States. Breeding facilities include the Peregrine Funds World Center for Birds of Prey, the Oregon Zoos Jonsson Center for Wildlife Conservation, the Los Angeles Zoo, and the San Diego Zoos Safari Park.
Despite population growth, the total number of wild California condors is still relatively small and the species requires intensive management for survival, including: 1 Monitoring a large proportion of condors in the wild to track resource use, identify behavioral problems, and detect mortalities; 2 biannual trapping for health screening, to test blood samples for lead, inoculate for West Nile virus, and to attach or replace wing tags and transmitters; 3 taking injured or poisoned condors back into captivity temporarily to administer treatment;
and 4 nest observations and interventions to maximize productivity in the wild Walters et al. 2010, pp. 972, 976, 982984; USFWS 2017, pp. 519.

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Habitat Use and Movement Ecology Along with our conservation partners, we have reintroduced California condors to a variety of habitats, including coastal mountains, old-growth forests, desert cliffs, and temperate montane shrublands and grasslands.
Within these habitats they can have enormous home ranges Meretsky and Snyder 1992, p. 321; Hunt et al. 2007, pp. 8487; Romo et al. 2012, pp. 4347;
Rivers et al. 2014a, pp. 496498 and often use different portions of their range for nesting and foraging Meretsky and Snyder 1992, p. 329; Snyder and Snyder 2000, pp. 140147; DElia et al.
2015, p. 96. Estimates of home range size varied among release sites 95
percent confidence intervals for southern California: 173,295282,760
acres ac 70,130114,429 hectares ha; Pinnacles National Park: 86,825
174,266 ac 35,13770,523 ha; and Big Sur: 42,61390,495 ac 17,24536,622
ha, probably as a result of geography, food availability Rivers et al. 2014a, pp.
496497, 500, years since the release program started, and flock size Bakker et al. 2017, p. 100.
Nesting habitat is generally characterized by steep, rugged terrain Wilbur 1978, p. 7; Snyder and Snyder 2000, p. 18; DElia et al. 2015, pp. 94
95. Within these areas, nests have been documented in various types of rock formations including crevices, overhung ledges, potholes, and in cavities or broken tops of giant sequoia Sequoia giganteus Snyder et al. 1986, pp. 235
236 or coast redwood Sequoia sempervirens trees Burnett et al. 2013, pp. 478479. Breeding adults segregate themselves into nesting territories, rarely crossing into the nesting territories of other California condors Finkelstein et al. 2015, Behavior.
California condors will generally use the same nesting territory in successive years as long as pairs remain intact, but will often switch nesting sites within that territory, regardless of whether they fail or succeed in their nesting efforts Snyder et al. 1986, p. 236.
California condors roost communally along rocky outcrops, steep canyons, and in tall trees or snags near foraging grounds, water sources, and nests Koford 1953, pp. 3536; Snyder and Snyder 2000, p. 167. California condors select roosts that offer winds or thermals favorable for soaring flight Poessel et al.
2018, pp. 4850, good peripheral visibility, where there is a long unobstructed space for taking off downhill and for approaching the roost in flight, and areas where there is some protection from high winds Koford 1953, pp. 3536. There may be trade-

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