Wednesday, January 4, 2017

Questions About Winter Bird Feeding

Back in September, I put out the bird feeder. I try not to do it too early because, well . . . bears. My feathered friends emptied it in hours. A couple of refills later and I decided I couldn’t afford to put out the buffet that early. The weather was warm; natural feed had to be available.

The birds, ever optimistic, still dropped by. I started writing dialogue for them:

Titmouse: “Nothing here yet. Still don’t know why he stopped.”
Chickadee: “He’ll refill it, he’s pretty reliable. He cares about us.”
Blue Jay: “I don’t know. He’s cheap.”
Me: “You blue jays are pigs.”

Feeding wild birds is immensely popular. According to a 2013 study by the Wild Bird Feeding Industry Research Foundation, some 48.9 million households in the U.S. and Canada buy wild bird seed each year, creating a healthy $4 billion annual market.

Dr. Emma Greig, project director of the Cornell Laboratory of Ornithology’s FeederWatch, calls it a “massive natural experiment” that may, or may not, be affecting bird behavior or benefitting particular species. No one really knows, she said.

“It’s really hard to make generalizations about how feeders change behavior, or even how feeders change reproductive success and survival,” Greig said. That’s because it’s difficult to do controlled studies comparing one population of a species with access to supplemental food to another without it. And it’s hard to tease out the effects of winter feeding from “all the other changes people are imposing on the natural world, including changes to habitat and climate. Those are affecting bird populations as well.” Another complication: there are hundreds of species of birds.

Greig said her intuition tells her that “supplemental feeding benefits some species, but developing a causal relationship is really, really tough.”

In Britain, studies have shown that winter feeding helps with blue tit survival and reproductive success — in some cases. In other cases it had a negative effect. Studies found that Eurasian blackcaps, a type of warbler, are overwintering in colder areas and in greater numbers where they have supplemental food, said Greig. Anna’s hummingbird has been increasing its winter range northward up the Pacific Coast and seems to be more prevalent in areas where there are people, she said. But are they increasing their range because of feeders? Or are people putting out feeders because they’re seeing more hummingbirds?

The Cooper’s hawk, an accipiter that preys frequently on small and medium-sized birds, has been increasing in numbers and more are wintering farther north. But is that because it can reliably find prey at bird feeders? Who knows.

Then there’s the issue of whether winter feeding facilitates the spread of disease. The answer here is squishy, too. One study found that house finch eye disease, a type of conjunctivitis, spreads more easily in aviaries where finches shared a feeder. But does that apply to wild birds? “If you have sick birds wiping their faces on perches used by other bids it could facilitate the spread of disease,” Greig said. But birds flock together anyway. And there’s certainly no shortage of house finches.

“There does seem to be more evidence that feeding birds and having bird-friendly backyards does more good than it does harm,” Greig said.

In spite of some built-in limitations, Greig said feeder-monitoring projects like FeederWatch still have scientific value. They can help generate data on how bird populations are changing, for instance, or generate observations on dominance and predation rates at feeders. Scientists can then use that to craft experimental studies to explore the questions in more depth and try to figure out the causal relationships. The trick is not to generalize, “because different species may respond in different ways to bird feeding.”

Backing up a bit, does start-stop feeding hurt the birds?

Probably not, said Greig. “As far as we know, birds will have an assortment of places they’re checking for food within their expanded winter territory. If one source of food disappears, they have others they can rely on.”

So, what do we know about the effect of winter feeding on the behavior of humans who do it?

Well, it seems to help bridge the human-natural world gap. The Cornell Lab’s Project FeederWatch has some 20,000 participants. They regularly count birds and note species at their feeders. They love it because it takes their hobby to a new level, said Greig. They learn more about birds and get more vested in their welfare and nature. And studies show that citizen scientists “are more likely to be environmental advocates and actually take action when it comes to environmental issues,” she said.

Joe Rankin lives in Maine. The illustration for this column was drawn by Adelaide Tyrol. The Outside Story is assigned and edited by Northern Woodlands magazine, and sponsored by the Wellborn Ecology Fund of New Hampshire Charitable Foundation.

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10 Responses

  1. I feed the birds year round. I also put out birdhouses for Bluebirds and others. Why? I enjoy watching them. Also, because humans are intruding on their habitat and I figure I’m compensating for that. Not all the birds that come around are feeding at the feeder. Robins, Flickers and others find food in my lawn because I mow it. If I didn’t mow, they’d have to look elsewhere. Sometimes our intrusions help the birds as much as intentional feeding does, but with different species.

    • Boreas says:

      I too enjoy bird boxes and have put them up on neighbor’s properties as well. Avoid any pesticides though, or you can end up killing them or the nestlings. At the very least, it will remove the insects that they eat. Bad news all around…

  2. Boreas says:

    FWIW, I no longer believe feeding birds or any wildlife is a very good idea. But being a bird-lover I still feed birds (and consequently all of the fuzzy-tailed rats on the property) occasionally throughout the year. Black-oil and or Nyjer seed perhaps once every 2-4 weeks in summer, maybe every week in winter and more with heavy snow or extreme temps. So the birds I feed typically are normal birds for my area and they often cache seed to eat later. The amount I put out is usually gone within a day – most going to the squirrels.

    Pulse feeding like this tends to minimize predators because it is erratic. I would think it would also lessen the probability of disease somewhat. All totally unscientific and gut feelings. I believe in the end it helps humans more than the birds.

    Over the last 20 years I have put a lot of effort into planting native trees, shrubs, and perennial flowers/weeds that produce food and cover year-round. If you have the ability to plant natural foods, I feel that would be the most you can contribute to birds, insects, and other animals. When warblers pass through in the spring and fall, they linger in the treetops eating all sorts of worms and bugs. I also leave dead trees standing for woodpeckers and other cavity-nesters. Dead and dying trees attract a lot of insects and the birds that eat them. I also keep reducing the amount of lawn I have and replacing it with perennials which enhance the food chain much more than a mowed lawn does.

  3. James Marco says:

    Yes, my wife feeds them and is a member of the Lab of Ornithology. Feeding some birds does help to transmit disease. For example the House finch eye disease was very prevalent about four years ago. It spread rapidly among the birds visiting my wife’s feeders. The next year, their numbers were much reduced. The following year they were up again, but no trace of the eye disease. Last year their numbers were diminished, but increasing over the previous year. This year they seem near normal.

    Blackbirds faced the same thing about 20-30 years ago. Their numbers were devastated by disease. About four years back, I noticed a couple mixed in to other flocks (cowbirds.) Now, they are near normal numbers and I expect them to recover well over the next couple years.

    Over the past 15 years, the hawks (mostly Redtail, some others-Peregrines, too) have been following the increase in the overall number of birds. The Junco’s have seemed to increase in numbers.. The Mockingbirds have declined. The Chickadees have declined. I saw Robins last January: weather variations or climate?

  4. Paul says:

    Apparently the number of birds killed per year by house cats is pretty astounding. My guess is that bird feeders contribute to this issue. If I was a cat that is where I would hang out!

  5. Charlie S says:

    House cats should be in the house not out running around killing birds, squirrels, chipmunks! Some people should not be allowed to have cats! And if they do let their cats out they should put bells around their necks. Responsible owners would do this!

  6. Wally Elton says:

    Just clean your feeders regularly. Bird feeding is done for people, not for the birds. But those who feed birds are likely to learn more about them and care what is happening to them. There are much more serious threats to bird populations than feeding them, especially climate change, habitat destruction and outdoor cats.

    • Boreas says:

      Agree 100% Another point to keep in mind is what is happening to birds that DON’T frequent feeders? Climate, habitat (summer AND winter grounds), pesticide use, and migration challenges are effecting many species dramatically, some for better, but many for worse. As in many plants and animals, species diversity seems to be suffering. Much is going on on the planet that we need to get our heads around.

  7. Charlie S says:

    ” Much is going on on the planet that we need to get our heads around.”

    Our heads around alright…around a television, around a handheld device, around a computer screen, around a football being passed around in a field… around around mindless we go, around around things laden with significance we’ll never know.

    • JohnL says:

      Can’t talk now Charlie. Watching the Giants/Packers game and texting with my kids. Maybe later.

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