Teetering on the Brink: A Massive Mortality Episode in the Captive Masked Bobwhite Quail (Colinus virginianus ridgwayi)
Masked bobwhite quail (Colinus virginianus ridgwayi) are a subspecies of quail originally described in 1884 by H. Brown in Sasabe, Sonora. Overgrazing by cattle, introduction of non-native invasive grass species, and drought made these quail increasingly rare. By 1900 they had disappeared from Arizona. Attempted translocations and reintroductions to Arizona and New Mexico in the 1930s failed. By 1950 the subspecies was considered extinct.
The birds were rediscovered in Rancho El Carrizo, Sonora in 1964. The Endangered Species Act of 1968 included the masked bobwhite quail. Sixty birds were captured in Sonora in 1968 and sent to Patuxent Wildlife Research Center for captive breeding. The entire captive flock was moved to the Buenos Aires National Refuge in 1996. Masked bobwhite quail have been bred in captivity for reintroduction for the past 25 years. Up to 2000 birds were produced for release each year since the program’s inception. Over 21,000 birds have been released over time on the refuge alone. A total of 30,000 birds have been released into the Altar valley of Arizona. To date, no effective wild population has been established. Current efforts are underway to locate more birds and/or proper habitat in northern Mexico.1
A disease outbreak in the Spring of 2007 reduced the flock from 680 birds to less than 300 in 3 weeks’ time. Amyloidosis, quail disease (Clostridium-associated enteritis), and inclusion body-associated salpingitis were the most important histologic findings. The remaining quail were bred during a shortened season and produced a total of 600 birds that have replenished the flock. Many of the recently identified genetic founders died during the outbreak. The genetic effect of the mortality is not known.
Only five to seven calling birds were detected in the wild in Sonora, Mexico during 2007—down from several hundred estimated only a few years ago. After decades of failed reintroductions in Arizona, the need to redirect efforts south of the border has become evident. For this reason, zoos are being asked to receive and manage parts of the captive flock. Suitable habitat needs to be identified and protected in Mexico. The current captive flock may represent the only hope for this highly endangered species.
1. Hernandez, F., W.P. Kuvlesky, R.W. DeYoung, L.A. Brennan, and S.A. Gall. 2006. Recovery of rare species: case study of the masked bobwhite quail. J. Wildl. Manage. 70(3): 617–631.