Food for thought( Millions of people tend bird feeders...)

Millions of people tend bird feeders in their backyards each year, often out of a desire to help the animals. But a new survey of research on the topic finds that feeding may not always bring a positive outcome for the birds.

Published as a Frontiers in Ecology and the Environment e-View paper (www.frontiersinecology.org), the meta-analysis led by Gillian Robb (Queens University Belfast, UK) and by Stuart Bearhop (University of Exeter, UK) reviewed results from more than 50 pieces of research conducted over the last decade.

In many cases, bird feeding was shown to have immediate positive outcomes. A number of studies indicated, for example, that chicks which were given supplemental food were far more likely to fledge than those that were not given extra food.

But feeding is a complex business and can lead birds to make poor decisions later in life. Attractive feeders can become ecological traps, encouraging birds to settle in an area that cannot support them once supplemental feeding has stopped. In those cases, feeders create a population level that cannot be sustained by natural levels of food.

There are also times when feeding can affect the timing of a birds life in unexpected ways. One study, for example, showed that Florida scrub jays breeding in suburban habitats with access to supplementary food breed earlier, but find themselves out of sync with natural food items which are important when rearing nestlings. This means the extra food can lead to a decrease in breeding success rather than an increase.

Surprisingly, the research team also found evidence in several studies which indicated that the flurry of activity caused by bird feeding does not increase the birds risk of predation. Counter-intuitively, the presence of feeders has been associated with lower levels of predation by domestic cats.

Robb and Bearhop say that the wide v
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