Female North American passerine birds have lower apparent survival than males

Survival is a fundamental organismal trait which can vary by sex, yet the extent of sex-biased survival is largely unknown across most taxa. To address this information gap, we leveraged 563 414 capture-mark-recapture records in 92 North American bird species-spanning 17 families across the orders Passeriformes and Piciformes-to estimate sex-specific apparent survival using transient Cormack-Jolly-Seber models. We found significantly lower apparent survival in females in 35 species. Adult apparent survival was, on average, 12.4% lower for females (0.479 ± s.e. 0.009) than males (0.538 ± 0.008), corresponding to adult lifespans (i.e. longevity having survived to adulthood) of 1.36 years for females and 1.61 years for males (18.5% higher than females). Exploration of potential mechanisms underlying sex-biased survival indicated that the female-male survival gap was greater in long-distance migratory species, lower in species with greater dispersal-associated morphology, and higher in species where males had relatively more fat, lending weight to the hypotheses that social dominance and lower movement costs in males contribute to male-biased survival. Our analysis demonstrates a pervasive male bias in adult apparent survival across a large swath of Nearctic breeding birds and provides possible explanations for previous observations of skewed adult sex ratios in birds.