Birds have a lot to do in their short lives: defend territories, build nests, raise chicks and feed themselves. But the toll of these activities may be greater for female birds than for male birds. A new study by UCLA ornithologists has found that female birds have lower survival rates than males. The research is the first to study female bird survival in a large dataset and shows that the phenomenon is more widespread than previously recognized. In mammals, females generally have higher survival rates, and why birds, which are not mammals, show the inverse is a puzzle the researchers are trying to solve.