ISRAEL VULTURE REVIVAL: They eat the dead, but now, many of them are dying out on their own. Vultures in Israel have been on the decline in northern Israel for years: A program at the Jerusalem Zoo is changing that. Researchers take eggs from mating vultures early in the season. That allows for the egg taken to be hatched in an incubator, while also giving the vulture couple a chance to lay another egg quickly. The couple would normally only lay one egg. The researchers at the zoo experiment with different conditions to hatch eggs most efficiently. It's important to set humidity correctly - the liquid inside the egg must evaporate at a normal rate.