Winter Bird Feeding: Good or Bad for Birds?

Winter bird feeding is hugely popular, with more than 40 percent of U.S. households participating. But is it actually good for the birds? Ornithologist Joe Smith looks at the science behind this backyard activity.

Winter bird feeding is one of the most popular ways for people to interact with nature, and most do it to help birds get through these tough months. But what does this really mean for conservation? Does feeding help or hurt birds?

More than 40 percent of U.S. households feed their backyard birds, and in the United Kingdom, the rate is as high as 75 percent.

Despite the widespread popularity of bird feeding, scientists are still building a basic understanding of its impacts.

As we might guess, a number of studies show generally positive impacts of bird feeding. For example, the overwinter survival of birds is enhanced by bird feeding.

This is especially true during the coldest times, when some hungry birds might otherwise lose the battle with the elements1.

A study conducted during winter in Wisconsin showed that black-capped chickadees with access to bird seed had a much higher overwinter survival rate (69 percent) as compared to those without access to human-provided seed (37 percent survival).

Furthermore, some studies have shown that birds making it through the winter in better physical condition see those benefits carry over into the nesting season.

Bird feeding produces significantly earlier egg laying dates, larger clutches of eggs, higher chick weights and higher overall breeding success across a wide range of bird species2,6.

Black-capped chickadee. Photo © The Nature Conservancy (Chris Helzer)
Black-capped chickadee. Photo © The Nature Conservancy (Chris Helzer)

The greatest impact of feeding is seen when birds are most challenged, such as after particularly harsh winters, or when birds are young and inexperienced, or when they are living in low-quality habitats2. Feeding can promote the survival and reproduction of the not-quite-fittest.

But in contrast to these straightforward results – showing that bird feeding makes for better-off birds – a few studies indicate that, at least in some situations, there may be unintended consequences of bird feeding.

A European relative of the black-capped chickadee, the blue tit, was studied in the United Kingdom to examine the impact of bird feeding on nesting success.

One research group3,4 found that birds fed during winter subsequently laid a smaller number of eggs that had lower hatching success and ultimately fledged fewer young than birds that weren’t fed at all. The offspring that did fledge weighed less and had a lower survival rate than the young of unfed birds.

An additional U.K. study of the blue tit and another chickadee-like species, the great tit, had similar findings.

Both species, when they had access to bird food, laid fewer eggs, had lower hatching success, and ultimately had fewer chicks fledged.

Great tit. Photo © Neil Tackaberry / Flickr under a Creative Commons license.
Great tit. Photo © Neil Tackaberry / Flickr under a Creative Commons license.

Note, however, that these are just two studies demonstrating a negative effect of bird feeding – among a majority that show positive effects.

Nonetheless, the striking findings of lower reproductive success in supplementally fed birds need some explanation. Unfortunately, it was beyond the scope of these U.K. studies to definitively explain how bird feeding resulted in lower reproductive success, but the authors offer several possible hypotheses.

One possibility the authors suggest is that the bird feeding provided an irresistible diet that was unbalanced – too high in fat to produce high-quality eggs. More protein, micronutrients, and antioxidants than are provided by bird seed may be needed to produce high-quality eggs.

Another possibility is that bird feeding allowed individuals with a lower reproductive capacity which ordinarily would not survive the winter the chance to nest.

A final possibility is that the feeders were placed in poor quality nesting habitat – leading the birds to choose these suboptimal sites as nesting areas in the spring.

More research needs to be done across a wider geographic area and on more species to understand not only the impacts of bird feeding on reproductive success, but also on other factors such as disease transmission, species range expansion, and population trajectories.

Citizen scientists can help by participating in initiatives like Project FeederWatch that ask people with bird feeders to share their observations. What you see in your own backyard can contribute to the efforts to answer these questions.

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References:

  1. Brittingham, M. C. & Temple, S. A. 1988 Impacts of Supplemental Feeding on Survival Rates of Black-Capped Chickadees. Ecology 69, 581.
  2. Robb, G. N., McDonald, R. A., Chamberlain, D. E. & Bearhop, S. 2008 Food for thought: supplementary feeding as a driver of ecological change in avian populations. Front. Ecol. Environ. 6, 476–484.
  3. Plummer, K. E., Bearhop, S., Leech, D. I., Chamberlain, D. E. & Blount, J. D. 2013 Winter food provisioning reduces future breeding performance in a wild bird. Sci. Rep. 3.
  4. Plummer, K. E., Bearhop, S., Leech, D. I., Chamberlain, D. E. & Blount, J. D. 2013 Fat provisioning in winter impairs egg production during the following spring: a landscape-scale study of blue tits. J. Anim. Ecol.
  5. Robb, G. N., McDonald, R. A., Chamberlain, D. E., Reynolds, S. J., Harrison, T. J. E. & Bearhop, S. 2008 Winter feeding of birds increases productivity in the subsequent breeding season. Biol. Lett. 4, 220–223.
  6. Ruffino, L., Salo, P., Koivisto, E., Banks, P. B. & Korpimäki, E. 2014 Reproductive responses of birds to experimental food supplementation: a meta-analysis. Front. Zool. 11, 80.

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119 comments

  1. Khrystuna says:

    Thanks. I will pass this article to my parents because they like to feed birds with leftovers. Khrystyna from https://piercee.com

  2. Marianne Guzzardo says:

    Great article. Love reading about birds and feeding my birds!
    Ttx

  3. ELMER KLASSEN says:

    IT IS POSSIBLE THAT SWARMS OF BIRDS AT MY FEEDERS,WILL LOSE THE ABILITY TO FORAGE IN OUR ULTRA COLD AND SNOWY WINTERS IN CANADA, SO WE HAVE CUT BACK AND THEY SEEM TO BE FEEDING IN THE LOCAL SHRUBS

  4. Brekken Spendlove says:

    What are the main things that makes birds sick?

  5. Virginia Woodrow says:

    I have two more ideas. 1) Maybe they have fewer offspring because the losses during the winter have dropped so much that they don’t need as high a population to begin with. 2) There may be some additive, heribicide, insecticide, preservative, etc. in the cheap bird seed that harms the birds. Not unlike the DDT problem.

  6. Justice Smith says:

    eh meh eh meh eh meh it did not really help my situation

  7. April Koch says:

    Also indoor cats are good for the birds and bird feeders are fun for my indoor cats! XD But for real it’s been awesome to see the Brown-headed Nuthatches coming to my feeder in North Carolina, where populations are apparently declining. They have to cross the street from the pine forest to get here, and I think at least one bird (Brown Thrasher) has been hit by a car trying to come to my feeder 🙁 But what are you gonna do? With the new housing and businesses popping up all over UNC, I don’t see any reason to stop helping out the guys who are holding on out there.

  8. John Tebbutt says:

    There are two differences between the feeding of wild birds in Wisconsin and the UK, which may be interconnected.
    First, the climate is very different. The extremes of weather which routinely occur in Wisconsin would be regarded as verging on the apocalyptic in the UK. The climate in the UK is much more akin to that in the Pacific Northwest: damp, rarely too got, rarely too cold. Also, while British gardens tend to offer a greater variety of plants, etc, lower Summer temperatures tend to mean they don’t get the colossal weight of bugs common in the US (until recently).
    Second, the type of feeding that goes on in the UK is somewhat different, relying heavily on peanuts, millet and suet balls. In general I would say that the quality and variety of food is lower than in the US. Many people feed stale bread to birds.
    I believe the feeding of peanuts in a damp climate means more mold?
    In conclusion, I think using these studies to compare the effects of winter feeding is like comparing apples and oranges. Not enough factors are controlled for.

  9. Tom Barrett says:

    Anything that connects humans to their fellow creatures has to be a plus. Bird-feeding leads to closer observation, which leads to awareness, which leads to … who knows … better habitat maybe.

  10. Peter Stonard says:

    The biggest issue is that feeders draw as many, if not more, invasive birds. Starlings and Asian Sparrows love bird seed and out compete the treasured bluebirds and martins of my area (Colorado). Asian sparrows are in direct competition for nesting sites with bluebirds. Really the only appropriate food in my area is thistle seed in a thistle feeder for the finches.

  11. Matthew A. Hernandez says:

    Thank you cool Green Facts for helping me learn more about feeding birds in the winter.

  12. Christy says:

    It would be interesting to follow up with a conversation about the effects of unintentional feeding of corvids, such as through poorly-managed food-waste or leaving pet food/chicken scratch accessible to jays and crows (etc.). Do these birds experience greater nesting success, with long-term secondary effects on other bird species?

  13. V Reynolds says:

    With a diversity of seed, fruit, nectar and suet favored by various birds, my 4 acre garden has become home to families of birds who stay with each new generation, while migratory birds return year after year for warm or cold months
    Native plants and trees help attract bees and butterflies
    The birds have housing, water sources and sanctuary, as well as hutches for ground feeders of all sizes Inc wild turkeys. The many feeders all have hoods protecting birds from rain and snow and the deck rail hayracks become a safe dry place for an afternoon roost off the cold snow. Plastic feeders work well in winter to prevent bird feet sticking to icy metal.

  14. Nature Mates says:

    Thanks for the great, informative article. We’re trying to educate the public here in Australia about the best practices of wild bird feeding. http://naturemates.com.au/best-practice/. It can be a contentious issue down here, mostly due to the lack of information and knowledge.