Table 3

Mean parameter estimates for rock and white-tailed ptarmigan during two years of high productivity and survival (representing 2004–05), and one severe year of low productivity and survival (representing 2006)
Parameter Rock ptarmigan White-tailed ptarmigan
2004 2005 2006 2004 2005 2006
SY hatched young (female) 1.34 1.21 0.90 3.25 ± 0.25 2.11 ± 0.59 1.18 ± 0.43
ASY hatched Young (female) 1.88 ± 0.44 1.67 ± 0.43 1.07 ± 0.34 3.33 ± 0.33 2.50 ± 0.59 1.50 ± 0.54
Juvenile survival (method 1) 0.40 0.48 0.18 0.41 0.17 0.14
Juvenile survival (method 2) 0.27 (all years) 0.27 (all years)
Adult female survival 0.67 ± 0.10 0.74 ± 0.09 0.41 ± 0.09 0.58 ± 0.22 0.55 ± 0.17 0.24 ± 0.10

These parameters were used in matrix projection models to predict population persistence under varying frequency of the severe year (see Figure 2). Juvenile survival estimates include values from the literature and therefore do not have associated standard errors. Because there were few SY female rock ptarmigan, rates were based as a proportion (0.8) of the ASY estimate using the results of previous studies (see text).

Wilson and Martin

Wilson and Martin BMC Ecology 2012 12:9   doi:10.1186/1472-6785-12-9

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