City Birds, Country Birds: Who Lives Longest?

American robin (juvenile) © 2014 Richard P. Weber

A study published recently in the journal Ecology reveals that some birds actually might live longer in urban or suburban settings, which ought to persuade those of us living in such areas to continue or strengthen our welcome of wild species in our yards.

Researchers used data collected over a 12-year period by “citizen scientists” to determine whether some species fared better in rural areas vs. much more heavily populated ones in the vicinity of Washington D.C./Maryland. Some native birds, like American crows, and nonnative species such as rock doves and house sparrows have long been known to flourish in urban areas. But for most bird species, the extensive loss of natural habitat and the increase of human disturbance generally cause profoundly negative effects on their lives.

In this study, four species coped better than their more sensitive country cousins. Gray catbirds (rarely found west of the Cascades) and northern cardinals (found mainly in the eastern half of the US) were found to live longer in urban areas than rural, whereas American robins and song sparrows apparently live longer in suburban spaces than rural. Three other east coast species studied showed no difference in longevity in the various habitats.

The study’s authors acknowledge that further study is necessary. For one thing, longevity doesn’t necessarily mean that the birds are successfully breeding and are without stresses; the study didn’t investigate the fecundity of the birds (reproduction often declines due to constant city noise and the acoustics of human-made hard surfaces, both of which make it difficult for birds to communicate), and the birds they studied are those that have adapted, to some extent, to the presence of people and our machines, impermeable surfaces, and lights. Needless to say, the multitude of species that need quiet, undisturbed habitat, or have very specific needs can’t be studied in populated areas since they typically wouldn’t be found there.

Nonetheless, the results show that some species are more adaptive to our presence than others (such as the varied thrush that requires dark, peaceful, mature forests in which to breed). Although urban and suburban areas generally host more predators (dogs, cats, and raptors attracted to bird feeders), roads and vehicles, noise, reflective glass, and chemicals, the more adaptive birds may respond well to backyard bird feeders, artificial nest boxes, dead wood, and water sources, and the renewed interest in growing native plants in our yards. It’s highly likely that they are also able to live longer because most of their natural predators have been driven away or killed off.

© 2014 Eileen M. Stark

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