Tuesday, April 08, 2008

Failing birds in the urban environment

In the urban environment it is often thought that the prevalence of predators has a significant effect on nesting outcome. So, the more magpies and cats, the less well birds’ perform.

A new American study questions this, arguing that it is the environment itself that has a greater effect. Monitoring the natural nests of migratory Acadian Flycatchers over six years they found that, compared to rural counterparts, urban birds were smaller and less resilient. They nested later, wouldn’t attempt second broods if the first failed, and wouldn’t return to an area again if they failed the previous year. All in all they “just didn’t seem to like the urban environment and gave up”. The presence /absence of notably predators was a minor, almost insignificant contributory factor.

The questions being asked now are why? Is it the noise, the amount of artificial lights at night, the local vegetation, the food source? All of which are likely to play a part but, the one question to ask now is: Is the urban environment becoming a sub-optimal habitat where only second-rate birds attempt to breed? The fitter individuals then controlling and breeding in a more prime suburban or rural environment.

Report published in: Journal of Animal Ecology.

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