Survival of sharp-tailed grouse Tympanuchus phasianellus chicks and hens in a fragmented prairie landscape
Doug L. Manzer and Susan J. Hannon
Wildlife Biology 14:16-25; 2008
We studied survival and probable causes of mortality for plains sharptailed grouse Tympanuchus phasianellus jamesi chicks up to 30 days of age, and for hens during the reproductive period in Alberta, Canada, during 1999-2001. We used the Kaplan-Meier function for estimating survival for > 1 radio-marked chick in the same brood and a bootstrapping technique to calculate standard errors while accounting for censored data. Chick survival was 47% over two years (95% CI: 29-64%) with 81% of mortalities occurring during the first 15 days. Predation accounted for 72% of chick mortalities with mammals taking the largest portion. Chick survival was similar when compared between landscapes with < 35% vs ≥ 35% crop and sparsely covered grassland (8 km2). Hen survival was 53% (95% CI: 44-63%) during the reproductive period over three years. Most hen mortalities were from predation (96%), with mammals accounting for the largest portion followed by raptors. Hen survival was similar in landscapes (8 km2) with < 35% crop and sparsely covered grasslands compared with those in areas with ≥ 35%. Our study helps clarify values of two critical vital rates, i.e. early chick survival and hen survival over the reproductive period.