A study published in the Journal of Evolutionary Biology is apparently the first to examin
e the effects of aging on the ability of birds to reproduce. The study, which focused on Blue-footed Boobies Sula nebouxii, found that “The DNA of the sperm of older individuals is damaged. This means their offspring have a greater likelihood of suffering from congenital illnesses.”
Females can identify the too-old males by their fading feet, and are less likely to choose males with that particular sign of aging. A few more details on this fascinating study can be found here.