Are their local birds in trouble when the feeders become empty? In other words, do birds become dependent on bird feeders for their food, particularly in the winter?
The answer to these questions appears to be no. Birds seem to know that they cannot count on even very rich food sources for long periods of time. Birds will not feed solely from a continuously stocked feeder. One study has shown that black-capped chickadees only take about 25 percent of their daily food requirements from well-stocked feeders. The birds are hedging their bets, looking for other sources of food in case a well-stocked feeder should become empty.
A definitive study to test for feeder dependency in black-capped chickadees was done in Wisconsin by Brittingham and Temple. These scientists studied two large populations of chickadees to monitor their survival.
For two years, one population was provided with sunflower seeds continuously. The other population was never given any food. In the third fall of the study, the feeders were removed from the first study area. So during the third winter of the study, neither population had access to supplemental food.
If the chickadees in the first population had become feeder-dependent, we would expect them to have lower survival than the population that never had the benefit of supplemental food.
Brittingham and Temple found there were no significant differences in winter survivorship.