All endangered birds tend to have eggs that fail to hatch: captive endangered birds produce more infertile eggs, whereas wild endangered birds have more failed hatchings due to embryo mortality (likely due to inbreeding).

Scientists used new techniques to visualise sperm and egg tissues, and found that eggs from captured endangered birds had not been successfully fertilised as very few, if any, sperm got to the egg.

This discovery may help conservation scientists increase the success of captive breeding programs.