Is ur­ban liv­ing bad for birds?

BBC Wildlife Magazine - - Our Wild World - Mike Toms

ARoughly one in five of the world’s bird species is found in cities, prompt­ing re­search into the ef­fects of ur­ban liv­ing. Gen­er­al­ists, om­niv­o­rous in diet, tend to adapt to ur­ban en­vi­ron­ments bet­ter than those with spe­cial­ist re­quire­ments. But even within these species, there are in­di­ca­tions that cities may not be good for birds’ health.

Re­searchers have found ev­i­dence that ur­ban pop­u­la­tions suf­fer from higher levels of ox­ida­tive stress com­pared to in­di­vid­u­als else­where, which neg­a­tively im­pacts their health. Re­cently, at­ten­tion has been fo­cussed on ‘telom­eres’ – the nu­cle­o­pro­tein struc­tures found at the end of chro­mo­somes. These pro­mote genome sta­bil­ity, and there is ev­i­dence as­so­ci­at­ing telom­ere length with life­span and mor­tal­ity rate.

If the pres­sures of ur­ban liv­ing mod­ify an in­di­vid­ual’s ox­ida­tive bal­ance, then this may re­sult in short­ened telom­eres – some­thing that has been found in ur­ban great tits and black­birds. But such health costs need to be set against all the pos­si­ble ben­e­fits – for in­stance, the avail­abil­ity of food at garden feed­ing-sta­tions.

Ur­ban liv­ing has its ben­e­fits, but great tits ( right) may be at higher risk of dy­ing young.

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