Physiological factors influencing female fertility in birds

Fertility is fundamental to reproductive success, but not all copulation attempts result in a fertilized embryo. Fertilization failure especially costly for females, we still lack clear understanding of the causes variation female fertility across taxa. Birds make useful model system research, partly because their large eggs are easily studied outside female's body, also wealth data available on productivity commercial birds. Here, review factors contributing infertility birds, providing evidence that traits understudied relative male traits, and avian research has been dominated by studies focused Galliformes captive (relative wild) populations. We then discuss key stages cycle where may be compromised, recommendations future research. particularly emphasize must differentiate between embryo mortality as hatching failure, non-breeding individuals should monitored more routinely possible. This lays groundwork developing clearer infertility, with important consequences multiple fields including science, conservation breeding.