Captive rearing sage-grouse for augmentation of surrogate wild broods: Evidence for success

Abstract

Both species of North American sage-grouse (Centrocercus spp.) have experienced declines in distribution and abundance. Translocation of adult birds from a stable population to a small or declining population has been a management tool used by wildlife managers to support population persistence in these areas. Captive rearing chicks and releasing them into wild surrogate broods is an untested alternative to augment declining populations of sage-grouse. We developed techniques to successfully rear sage-grouse chicks in captivity, evaluated explanatory variables that could influence hatch and captive-rearing success, and estimated the survival of domestically hatched (DH) chicks to 28 days of age following introduction to a surrogate wild brood. We collected 304 eggs from radiomarked female greater sage-grouse (C. urophasianus) during 2004–2007 in 3 study areas in northwestern Colorado. Estimated hatching success of collected eggs was 0.745 (SE = 0.022, 95% CI = 0.700–0.786) and was negatively influenced by the number of days an egg was stored and the percent egg weight loss that occurred during storage and incubation. We monitored 175 DH chicks in captivity for 1–10 days before introduction and adoption into surrogate wild broods. Model-averaged captive-rearing success was 0.792 (SE = 0.045, 95% CI = 0.686–0.865) across years, and was positively influenced by initial chick mass at hatch and daily weight gain in captivity but negatively influenced by the number of days the egg was stored and advancing hatch date. We were able to radiomark and monitor 133 DH chicks adopted into surrogate wild broods until 28 days of age. Eighty-eight percent of DH chicks were successfully adopted within 24 hours. Our overall estimate of DH chick survival to 28 days (0.423; 95% CI = 0.257–0.587) was comparable to published wild-hatched chick survival. Predation and exposure-related deaths accounted for 26.3% and 25.6% of the known fates, respectively. Our captive-rearing protocols and techniques were successful for collecting greater sage-grouse eggs, hatching and rearing chicks in captivity, and releasing chicks into wild surrogate broods. This success further implies that captive rearing and release can be a potential management strategy to demographically and genetically reinforce or augment small populations of sage-grouse. © 2015 The Wildlife Society.