Bird species colonizing urban areas need their vitamin E
Birds A fascinating study from the journal Oecologia finds evidence that differences in levels of vitamin E and other antioxidants explain which birds are able to successfully invade and persist in urban environments.
Anders Pape Møller and fellow researchers hypothesized that urban areas, given their warmer microclimates, higher levels of pollutants, and longer breeding seasons, should place greater oxidative stress on birds which in turn should favor invasion by those species that have better access to antioxidants.
To test their idea, they looked at liver samples of dead birds from urbanized and non-urbanized species in Denmark. They found that urbanized species had higher levels of vitamin E and total carotenoids than similar non-urbanized species. This suggests that higher levels of antioxidants help certain species colonize urban environments.
Furthermore, urbanized populations had lower levels of antioxidants than rural populations of the same species. This suggests that when populations of birds colonize an urban area, they begin to face greater stress than counterparts from the same species in rural areas. However, birds from species that had urbanized for a longer period of time had higher levels of vitamin E, which could mean that the population adapts over generations to the environment.
The researchers found further evidence of the importance of antioxidants for survival by examining birds that had been killed by cats. They found that these birds had lower levels of vitamin E than birds who had died from other causes such as flying into windows.
This study provides a groundbreaking perspective on why some birds are able to colonize and persist in the urban environment and others are not. This may help explain future patterns in bird populations as the world continues to urbanize.
--Reviwed by Rob Goldstein
Møller, A., Erritzøe, J., & Karadas, F. (2009). Levels of antioxidants in rural and urban birds and their consequences Oecologia DOI: 10.1007/s00442-009-1525-4
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