Age-specific survival in breeding Black-capped Chickadees (Parus atricapillus)

I followed the survival of 153 Black-capped Chickadees (Parus atricapillus; 68 males, 85 females), which had bred at least once in or near my study area. All were of known age, and had been banded during a 10-year period, (1980-1981 through 1989-1990). Male breeders lived an average of 3.19 +/- 1.85 years (n = 68), while female breeders averaged 2.53 +/- 1.98 years (n = 85). Most of this difference was due to differential mortality during and immediately after their first breeding season; female breeders suffered a significant peak in mortality during this period, while males showed no particular peaks in mortality associated with any given season or age class. Two factors had a significant effect on female survival in their first breeding season: high initial rank in the previous winter's nonbreeding necks; and being mated to a male with prior breeding experience. Moreover, oversummer mortality of young females mated to inexperienced males was significantly higher in years with cold spring weather (mean low temperature in May 7 degrees C or below) than in years with warmer spring weather (mean low in May >7 degrees C). This suggests that inexperienced males may provide less food for their mates during egg laying and incubation than do experienced males, and that the effect on females of lower provisioning by inexperienced males is worsened by harsh weather conditions. The relationship between provisioning level and male experience also may carry over to the nestling period. The cost to a female of producing a particular brood size will, therefore, vary both with her own status and with the degree of experience of her mate. Hence, the relative cost of increased fecundity should vary from population to population, depending on the local proportion of young females and experienced breeding males.