Lead, trash, DDE, and young age of breeders linked to lower fertility in the first two decades of reintroduction for critically endangered California Condors in California.

This article presents a comprehensive analysis of 20 years (1999–2018) of reproductive data from reintroduced flocks of the critically endangered California Condor (Gymnogyps californianus) in southern and central California. The study identifies several anthropogenic factors linked to reduced fertility, including lead poisoning (primarily from ingestion of lead-based ammunition in carcasses), ingestion of trash by chicks (notably before trash management began in 2007), and exposure to DDE (a contaminant associated with marine mammal feeding by coastal females) which lowered hatching success. Additionally, reproductive rates increased with age and experience, with younger breeders and new release sites showing lower recruitment and breeding success. The findings suggest that addressing lead poisoning and other threats, alongside the natural aging of the population, will be critical to improving reproductive success and achieving self-sustainability in this reintroduced population.