Blackbirds live longer in cities than in forests. But their telomeres, the repetitive stretches of DNA at the ends of the chromosomes, show that these city birds are in poorer health than their rural cousins.
These findings from a study in five European cities led by University of Groningen biologists were published in Biology Letters on 21 March.
Blackbirds are a common sight in many city gardens. The species has adapted well to this environment. “But they also live in their original forest areas, which makes them ideal candidates for a study of the effect of city life on health”, says University of Groningen postdoc Juan Diego Ibáñez-Álamo. He travelled to Granada, Seville, Madrid, Dijon and Turku to obtain blood samples from blackbirds in these cities and the adjacent rural areas.
Ibáñez-Álamo is working on a project studying the health effects of city life on birds at the Groningen Institute for Evolutionary Life Sciences. “There are many indicators of health, like the presence of parasites or the immune response, but these will vary over time.” The only truly unambiguous marker of health is the length of the telomeres, DNA structures that form a kind of cap at the end of the chromosomes and protect the DNA molecule from deterioration, just like the plastic caps on shoelaces.