June 24, 2013
Study Questions Benefits Of Feeding Wild Winter Birds
Brett Smith for redOrbit.com - Your Universe Online
Freezing temperatures and a layer of snow may make us feel sorry for any birds that remain up north during the winter months, but a new study in the journal Scientific Reports has found feeding these birds may not convey any benefits with respect to breeding.A three-year study that was conducted across nine woodland sites in the United Kingdom by researchers at the University of Exeter and the British Trust for Ornithology found feeding wild blue tits in the winter resulted in less successful spring breeding.
"Our research questions the benefits of feeding wild birds over winter,” said lead researcher Jon Blount, from the University of Exeter. “Although the precise reasons why fed populations subsequently have reduced reproductive success are unclear, it would be valuable to assess whether birds would benefit from being fed all year round rather than only in winter.”
In the study, wild blue tits were left unfed, given plain fat balls as a supplemental food source, or given fat balls enriched with vitamin E – a nutrient commonly found in nuts and seeds. The British researchers distributed both nesting boxes and bird feeders across the nine sites. The birds’ reproductive success was determined by examining the nesting boxes in the spring, counting the number of viable eggs laid and tracking the growth of hatched chicks.
“The timing of laying and clutch size also did not vary in response to food supplementation,” the team wrote in their report. “Hatching success was marginally higher in fat plus vitamin E-fed populations compared to the other treatment groups.”
The team also noted the supplemental feeding groups tended to produce lighter, smaller chicks – ultimately resulting in 8 percent fewer offspring.
"There could be a number of different explanations for our results,” said co-author Kate Plummer, from the University of Exeter. “One possibility is that winter feeding may help birds in relatively poor condition to survive and breed.
“Because these individuals are only capable of raising a small number of chicks, they will reduce our estimation of breeding success within the population,” she said. “But more research is needed to understand whether winter feeding is contributing to an overall change in the size of bird populations."
The study’s findings could have implications for the billion-dollar bird feed industry.
“As the wider scientific evidence shows, feeding wild birds with appropriate foods delivers a range of positive benefits,” said Jane Lawler, a marketing director at bird-feed maker Gardman. “A number of unanswered questions remain, however, and this is why we have been supporting this and other research, using the information gained to inform our products and the advice that we provide to our customers."
Other studies have shown feeding wild birds in winter can immediately increase their odds for survival and boost future breeding odds. In a statement, the researchers said their results simply provide important new information and inform the debate.
“More research is needed to determine exactly what level of additional food provisioning, and at what times of year, would truly benefit wild bird populations,” Blount said.