Fitness heterogeneity in adult Snow and Ross’s geese: Survival is higher in females with brood patches

Abstract

AbstractLife-history theory broadly predicts a fitness tradeoff between costs of raising offspring and parental survival. Waterfowl with precocial young face particularly high costs of egg production, incubation, and brood-rearing, but not all evidence supports a corresponding decline in survival. We used multi-state mark–recapture–recovery models to estimate annual probabilities of survival, reported mortality, and transition between 2 states for female Ross’s Geese (Anser rossii) and Lesser Snow Geese (A. caerulescens caerulescens) that attempted nesting near Karrak Lake, Nunavut, Canada. States were possession of a brood patch (high likelihood of successful nesting, “B”) vs. no brood patch (attempted nesting but failed, “N”). Based on over 43,000 birds marked from 2000 to 2015, we found that females of each species with a brood patch had consistently higher probabilities of survival than those without, subsequent to capture in early August. Virtually all of the state differences in survival were due to nonhunting mortality. These patterns are consistent with the concept of variable individual quality impacting vital rates across multiple seasons. Higher survival of females with brood patches may be linked to greater breeding success but also to a hypothesized dominance advantage afforded to family groups of geese during winter. Moreover, although hunting pressure can play a key role in regulating Arctic goose populations, it does not appear to affect this relationship between inferred breeding state and survival. Instead, coincident with recent declines in harvest rate in these populations, higher individual quality of breeding females appears to outweigh the higher hunting vulnerability of presumed parents with young. The potential influence of social dominance in reducing natural winter mortality among families may thus contribute to the survival advantage seen in successful, relative to failed, breeders.