CSM - A downside to bird feeders

A downside to bird feeders (from Christian Science Monitor)

Backyard bird feeders have become almost as ubiquitous as garden hoses. One result: the northern cardinal's range has grown significantly since the early 1960s. Yet scientists know little about the long-term effect the explosion in feeders is having on bird populations.

So a group of biologists in Britain has pulled together a look at what is known. They find that most of the effects from supplemental feeding seem to be positive. But seed-laden feeders have the potential to trigger long-term changes in species' range and breeding patterns.

In reviewing studies from the past 30 years, the team finds that supplemental feeding led female birds to lay eggs significantly earlier than is typical for their species. For some birds, such as Florida scrub jays, this put the young out of sync with the natural food sources they needed at that stage of their development. For one species of flightless parrot in New Zealand, a feeding campaign to increase the birds' population actually led to the birds hatching more males over time than females.

The biologists add that some of the less desirable effects of supplemental feeding could be reduced if more people follow best-feeding practices, such as those outlined by Project Feeder Watch, led by researchers as Cornell University. The results appear in the current issue of Frontiers in Ecology.– Peter N. Spotts