Life history and ecology shape global patterns in avian hatching failure rates.

Abstract

BACKGROUND: Hatching failure is common in the eggs of wild birds, yet its variation in relation to ecological and life history factors remains poorly understood. Understanding these patterns is essential for explaining reproductive strategies and evolutionary trade-offs in birds. RESULTS: In a comprehensive comparative study, we found that the previously recognized latitudinal decline in avian hatching failure rates is driven by a greater proportion of eggs failing in larger clutches at lower latitudes. We suggest that this pattern could reflect higher exposure to ambient conditions in larger clutches, which might have more severe consequences for egg viability in warmer environments. Furthermore, hatching failure rates increased with species longevity. We predicted this from the notion that, if needed, short-lived species should invest more heavily in current reproduction, whereas longer-lived species should be more prone to prioritize self-maintenance to improve future breeding opportunities. Hatching failure rates were also higher in species with uniparental incubation compared to biparental species, higher in elevated nests than in ground nests, and negatively related to altitude. CONCLUSIONS: Our results reveal several novel patterns of variation in hatching failure rates in relation to aspects of ecology and life history. These results suggest that clutch size, latitude, and parental care strategies interact to shape reproductive success and highlight potential evolutionary trade-offs between current and future reproduction. Further research is needed to clarify the proximate mechanisms underlying these patterns and their implications for avian life history evolution.