Food for thought

Apr 03, 2008

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, the meta-analysis led by Gillian Robb (Queen’s 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 bird’s 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 variety of outcomes they discovered in their work point to a real need for more comprehensive research on the topic. Although bird feeding itself may seem somewhat marginal, an incredible number of people do it. Surveys conducted in the US in 2003 revealed that more than 43 percent of those asked give birds some kind of food. In the UK, surveys indicate that as much as 75 percent of the general public feeds the birds.

“Changing the natural dynamics of food supply at such a large scale represents a major intervention in the ecology of birds,” says Robb. “But we have a remarkably limited understanding of the impacts of bird feeding.”

There have been relatively few studies conducted which incorporate urban and suburban yards, for example, and very few studies have run for more than one or two years or considered more than one species. Robb and Bearhop plan to continue their investigations at field sites in Northern Ireland and Cornwall.

“It seems highly likely that natural selection is being disrupted,” Robb says.

Source: Ecological Society of America

Explore further: Climate change redistributes fish species at high latitudes

add to favorites email to friend print save as pdf

Related Stories

Snack attack: Bears munch on ants and help plants grow

8 hours ago

Tiny ants may seem like an odd food source for black bears, but the protein-packed bugs are a major part of some bears' diets and a crucial part of the food web that not only affects other bugs, but plants too.

Satellite telemetry tracks bearded vultures

Jan 16, 2015

The Pyrenees are home to continental Europe's only wild population of bearded vultures, a species classified as endangered in Spain. A study compiled by Spanish researchers reveals - in a level of detail ...

Migratory birds' fuelling station empty

Jan 12, 2015

Millions of Australia's migratory shorebirds are being pushed closer to extinction as the quality of their primary feeding grounds, or 'refuelling areas', in East Asia continue to decline.

Recommended for you

Orangutans take the logging road

32 minutes ago

A new discovery by a Simon Fraser University doctoral student in the School of Resource and Environmental Management, published in Oryx, demonstrates that orangutans may be even more adaptable than he fir ...

Picking up on the smell of evolution

1 hour ago

UA researchers have discovered some of the changes in genes, physiology and behavior that enable a species to drastically change its lifestyle in the course of evolution.

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

Argiod
1 / 5 (1) Apr 04, 2008
We must consider in this equation the fact that humans are also a part of nature. Therefore, whatever we do is, by definition, natural. Ergo, large numbers of humans feeding birds, or other animals, is part of nature's process. For us to suddenly stop an age-old habit might have significant effect on birds that have come to depend on us for sustinance.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.