Darker colored pigeons are healthier

A study of urban pigeons in central Paris has shown that birds with higher levels of the dark pigment melanin have stronger immune systems. They are also better able to fend off parasites. The researchers say the findings may help explain why different colored birds have adapted to different environments. The researchers explored why birds of the same species are often colored differently. By assessing the coloration and state of health of 195 free-living urban pigeons, they found that darker pigeons had lower concentrations of a blood parasite called hemosporidian. Their immune systems also responded faster to infection, compared to their pale-feathered cousins. The research suggests that the birds may have evolved to produce higher levels of melanin in order to protect their immune systems. This could also explain why there are higher populations of dark feathered birds in urban areas, where parasite prevalence is higher. The finding that immune responsiveness and parasite intensity correlates with coloration suggests that melanin-based coloration could play a role in sexual selection. So darker birds may be healthier and also appear more attractive to the opposite sex.