What is the Impact of Backyard Birdfeeders on Local Birds?

Posted by
Rosemary Drisdelle
Nov 23, 2008

Many people enjoy feeding wild birds and the hobby is increasing. Some assume that we are helping wild birds to survive by providing them with a reliable source of food; others acknowledge that birds know where to find food on their own and we are really only feeding them for our own enjoyment. Whether they really need the food or not, the millions of dollars worth of birdseed and other foods put out every year must be having some effect. Now scientists are asking what the effect is.

Not surprisingly, studies have turned up both positive and negative effects. Among the negative impacts:

Abundant food at the beginning of the breeding season can induce birds to breed earlier than normal. Unfortunately, chicks may need different food than their parents (seed versus insects), so early chicks may hatch before there is enough food for them to survive.

Because birdfeeders bring many birds to the same place to feed, they can help spread infectious diseases that kill birds.

In some bird species, an abundance of food can result in a shift in the male : female ratio.

Positive effects of feeding include:

Early nesting and good nutrition increase the chances that birds will produce a second clutch of eggs in the same season.

More eggs are laid, and eggs tend to be larger and of better quality.

We don’t necessarily need to stop feeding birds, but we do need to know more about both the direct and indirect effects of this activity.

For more information, see

“Food for thought: supplementary feeding as a driver of ecological change in avian populations.” GN Robb, RA McDonald, DE Chamberlain, and S Bearhop. Frontiers in Ecology and the Environment. 6 (2008): 476-84.