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.
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.
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.
I thought it would be good to join the feeder watch, since I have seen some very unique birds for my area of the country. However, I object to having to pay a fee for giving you free data.
Hi Joe, very useful information, thanks. I think you may be right that the studies showing negative impacts of feeding birds may be influenced by a number of factors. We find that if birds are fed a varied and balanced diet then they generally thrive and create a long-lasting colony. It may be that some commercial mixes are too high in fillers/carbohydrates and not high enough in proteins and minerals. We find that for the winter, mealworm rich mixes, niger seeds and nuts aid in the local bird population’s survival.
On another note, trying to promote people helping our native greenfinch populations here in the UK which are showing alarming declines, would be great if you could share http://www.littlepeckers.co.uk/blog/wild-bird-mix-helping-greenfinches/
Thanks
David
Sooooo, To feed, or not to feed must be the question…..what do you suggest???
Interesting speculation about herbicides and pesticides in feeder seed…but how about the big picture with regard to lawn and garden care? If we are luring birds into the yard with food and habitat for our viewing pleasure, I think it’s prudent to ditch the residential chem use so prevalent in hopes of achieving that “monoculture golf course” look many desire. Non-toxic lawns with 39 different plants growing in them are actually interesting to me and the beetles and grubs living in them provide a nice balance of real living protein for birds visiting the seed feeders. Nothing like backyard birds taking Cotinis nitida in flight, it’s a pleasure to watch.
Not denying the possibility of feeder nutrients alone being responsible for some of the negative data noted in studies, but I’d like to see a broader consideration of factors potentially responsible for such effects. Lots of nasty stuff can jump into the food chain when human activity in an area is considered and analyzed, every spring those lawn care flyers are mailed to any house with more than three blades of grass growing. Nearby agricultural use of chems and effective concentrations required? Wow! It’s scary for human health, too.
Could be that the feeder seed is the safest stuff around and it’s everything else we do that causes the problems in residential areas. Even after years of providing seed, I notice a huge shift in foraging behavior when live protein is available in the area thus skeptical of the “diet training” theories pertaining to birds. A midwinter stonefly hatch will result in backyard feeders being completely ignored by most every species as they head to the creeks to gorge themselves. Birds seem to exploit near every food source imaginable in an area and some we don’t even think of, thus it’s difficult to narrow down the problem.
There is another important aspect to the impact of bird feeding: the birdseed may be grown using large scale monoculture agriculture, with all the attendant consequences. This kind of agriculture replaces birding habitat with a very limited environment which may support a few migratory birds, but probably not the birds that would thrive in a more diverse habitat.
So I feed, but I worry 🙂
Could there be a parallel with other creatures who tend to produce more offspring when they are over-hunted or have high losses do to adverse weather, lack of food, or loss of habitat? The coyote comes to mind. “Adapt to survive”.
Great information! I will go out and fill the feeders now!
I heard that if you feed the birds all summer you must feed them in the winter. Is it best to just feed them in the winter and let them fend for themselves in the summer?
Hi, My husband and I live in Riverton, Wyoming.
we began feeding birds in late fall of 2014 and continued through spring2015 . In fall 2015 we began again and are still feeding. Habitat is good, year round water and lots of vegetation. I am beginning to think it may not be a good idea to feed. We have tons of common sparrows and some races. But this year I have seen NO chickadees!! Is it climate change or is it my over feeding the sparrows?
Another strong possibility is that bird seed is probably produced using pesticides.
I live in SE Michigan in a semi-rural area near a lake. There is a wild area behind our property that is mostly wooded . I have a feeder pole at the back of my yard and I keep it stocked most of the year and all of the Winter. I have a suet feeder , a thistle feeder and a regular seed feeder. My regular feeder holds about 3 pounds of seed and I sometimes fill it twice a day. I get a wide variety of birds but mostly Sparrows of course. I get Cardinals , Finches, Chickadees, Doves. BlueJays , and Woodpeckers too.
And plenty of squirrels on the ground. My metal pole is too slippery for them to climb …I finnaly won that battle. I feel that the sheer amount of birds I get tells me that my location is important . I don’t like the expense but I enjoy seeing them and feel good about feeding.
If our gardeners planted more native plants and shrubs, the birds would have a better chance of finding natural food sources in the winter. If our gardeners left their spent plants standing through the winter, our birds would have an opportunity to pick at the seeds. We are taking away the open areas where birds can feed. We manage our gardens so they look good without a thought about natural habitats. We need to support birds somehow as we continue to take away their habitat. Research points one way, then another in many studies. I’m going to carry on and wait for more definitive recommendations.
As a long-time contributer to Cornell projects (on and off for more than 18 years; I once *meticulously* maintained a high of 15+ feeding stations on our 5-acre “certified wildlife habitat” property for ~8yrs for Project Feederwatch), and student who loved ornithology, systems thinking, and forest ecology studies in college (B.S. Env. Studies, UNH), who later worked for a very popular birding store for several years, and eventually became a trained speaker on wildlife conservation topics for UNH Cooperative Ext and NH Fish & Game, my opinion is it all depends on what you’re using for seed, whether you cycle on and off properly, and how sanitary you keep your feeders. Low quality, i.e. “cheap,” seed from big box stores, fed 24/7/365 in poorly maintained feeders, whether it’s NBD or not, is bigtime bad for birds, primarily in terms of disease, but also in terms of interfering with nature in general.
Thanks for the article. I appreciate the attention paid to the other habitat-related issues.
J. Eno
Greenland, NH
We have found that supplemental winter feeding in our area of southeastern Pima County, Arizona, has produced larger egg clutches and higher numbers of healthy, viable offspring among our local Gambel’s quail, cactus wren and house finch populations.
I’ve been feeding birds on my one acre backyard for over 23 years, it is a sanctuary for wild life, tons of flowering plants have been planted over the years to feed and maintain their life style, it’s been a trial of errors figuring out what to plant and not as between the chipmunks, squirrels rabbits and an occasional deer they can really wipe out a landscape masterpiece in one evening. I feed seed mainly thrown on the ground at different places thruout the sagebrush and around trees, away from the main yard, feeding in the brush gives them sufficient cover from the predatory birds that hunt them which I have witnessed on occasion, ? But that’s nature. Anyway I can really babble on about all ” my” wildlife, I enjoy it and I don’t feel like inhibiting their natural environment.