Long-term Study Finds Female Birds Die Earlier Than Males Across Many Species

Using more than 563,000 bird-banding entries gathered by the Institute for Bird Populations, a UCLA team discovered that adult female birds across 35 North American species experience a 12.4% lower survival rate than males, averaging 1.36 versus 1.61 years after reaching adulthood. Lead author Joanna Wu noted the pattern was consistent among flycatchers, warblers, cardinals and tanagers, and was strongest in long-distance migrants, species with rounded wings, and those where males store more fat.

Researchers suggest that the energetic demands of egg production and extended migration increase female risk, while the ZW sex-chromosome arrangement may also influence lifespan. The work, funded by the National Science Foundation and published in Proceedings of the Royal Society B, raises concerns that female-biased mortality could worsen bird population declines driven by habitat loss and climate change.