Authors: Marshall, Ashleigh; Balloux, Francois;Hemmings, Nicola;Brekke, Patricia;

Avian hatching failure is a widespread phenomenon, affecting around 10% of eggs that are laid and not lost to predation, damage, or desertion. While it is acknowledged that rates of hatching failure are often higher in threatened species and captive populations relative to wild, non-threatened populations, these differences have rarely been quantified and any broader patterns remain unexplored. We conducted a phylogenetically controlled multilevel meta-analysis across 234 studies and 246 species. We found the mean overall rate of hatching failure to be 17%, with threatened species experiencing significantly higher rates than non-threatened species. Across management levels, wild populations experienced the lowest rates of hatching failure, followed by wild managed populations, with captive populations experiencing the highest rates. Similarly, populations undergoing artificial incubation, supplementary feeding, and artificial nest provision displayed significantly higher rates of hatching failure than populations without these interventions. This is the most comprehensive comparative analysis of hatching failure conducted to date, and the first to quantify the associations with threat status and management. We discuss the implications of our results, such as their potential use as a tool for conservation managers when assessing the effectiveness of applying various interventions and determining the best conservation strategy for a species.