By Stanley Temple
Many people feed birds during winter, believing they’re engaging in an activity that is good for them as well as for the birds.
Yet, while there’s no doubt that people enjoy the sights and sounds of birds at a feeder, what about the birds? Does winter bird feeding really do them any good? Or can it actually harm them?
There are many potential pluses and minuses to consider.
Possible upsides and downsides of winter feeding
The potential benefits of winter bird feeding include:
- Better survival of birds over winter
- Increased survival during periods of extreme weather
- Improved reproduction during the following breeding season
But there are also potential risks associated with winter bird feeding, including:
- Higher risk of death from diseases spread by contaminated food or feeders
- Higher risk of death from unnatural accidents (e.g., collisions with windows) or from predators attracted to the concentration of prey — i.e., birds
- Increased dependence on supplemental food, impairing a bird’s ability to use natural food
So what’s the answer: Is feeding birds in winter good or not so good? My student Margaret Brittingham and I did one of the first comprehensive studies of the benefits and risks of feeding birds in winter, focused on black-capped chickadees in Wisconsin.
Feeding does boost survival, but…
Here’s what we found. During the three winters of our study (1982-85), 418 banded chickadees with access to a feeder survived better than 158 without supplemental food. On average, 69% of chickadees with access to a feeder also survived over the winter (October through April) compared to only 37% without supplemental food.
But that’s just part of the story. That big difference in the birds’ overwinter survival was almost entirely due to how well they fared during brief extreme winter conditions; i.e., when it stayed below 0 degrees Fahrenheit for five days or more. In contrast, during milder winter conditions we saw no difference in survival rates between the two groups.
Our results suggested that chickadees with access to a feeder survived better during severe winter weather because they were fatter and had to spend less time and energy foraging for scattered, natural foods. At the same time, we found no evidence that birds with access to a winter feeder had better breeding success the following spring.
No one who has fed birds can deny the risks involved. Massive die-offs of birds have occurred at feeders because of disease outbreaks, and birds suffer inevitable accidents involving windows, cats, and natural predators like hawks. However, we found that, on average, the increased ability of feeder birds to survive winter more than offset losses due to disease and accidents.
Reduce the risks of winter bird feeding
It’s important to note that we were very careful to maintain our experimental feeders so that the risks of diseases and accidents were minimized. Evidence from this same study showed that the risk of disease mortality rises significantly if a feeder is installed that birds can easily contaminate with their droppings. This risk also grows if people fail to regularly clean and disinfect their feeders.
What this says is that if your feeder poses an elevated risk to birds, you may erase any benefits of winter feeding and even have a negative impact on birds. This could be especially true during “normal” winters without prolonged and extreme low temperatures.
Lest you worry about turning you feeder birds into “dependent beggars” which can no longer fend for themselves, we saw no evidence that feeder birds became overly reliant on supplemental food.
In our study, birds with ready access to a feeder never obtained more than 20 to 25 percent of their energy needs from it; the remaining 75 to 80 percent came from natural sources, even though the birds had ample opportunity to take more from feeders.
In other words, even feeder birds use the feeder as a supplement to their natural diet, not a replacement.
So, feeding birds is a relatively neutral activity, except during especially severe stretches of winter weather. But it’s crucial that your feeder not pose risks, as this can easily turn winter feeding into an activity that harms birds more than it helps.
University of Wisconsin emeritus professor and wildlife expert, Stan Temple, writes and speaks frequently about birds, wildlife ecology, and conservation. Contact him at firstname.lastname@example.org.