Winter food provisioning reduces future breeding performance in a wild bird
Author(s): Plummer, K.E., Bearhop, S., Leech, D.I., Chamberlain, D.E. & Blount, J.D.
Published: January 2013
Journal: Scientific Reports Volume: 3
Article No.: 2002
Digital Identifier No. (DOI): 10.1038/srep02002
A new study by scientists at the University of Exeter, in collaboration with the BTO and the University of Turin, has found reduced breeding performance in woodland Blue Tits given access to extra food the previous winter. Birds were provided with fat, fat with added vitamin E, or no additional food. The following spring, Blue Tits with access to extra food produced young that were smaller, weighed less and had lower fledging success than adults that were not fed.
This study demonstrates a carry-over effect of winter feeding, but the exact reasons for the reduction in breeding success reported are not clear. One possibility is that the fed birds received an unbalanced diet. Alternatively, extra food could have represented an ecological trap, encouraging birds to invest energy in reproduction at a level that could not be sustained once the food was withdrawn. Finally, winter feeding could have altered the structure of the breeding population, by allowing adults in poor condition that would not normally have been able to reproduce to do so, reducing the overall estimation of breeding success within the population.
The results of this study provide important new information and inform the debate around the role that feeding wild birds may play in their population processes. However, more research is required to properly understand the effects, beneficial or otherwise, of the multi-million pound bird food industry on bird populations.