I was surprised to quite a sizable area in my local hardware store allocated to bird feed and feeders. Feeding the birds is big business in the U.S. where a surprising 34% of households reported buying some bird seed in 2013 (according to U.S. Fish and Wildlife Service data). That amounts to expenditures of $3.2 billion on bird seed and $1.1 billion on bird feeders! Hardly tuppence. Canadians apparently really love their backyard birds, because the same study showed that a whopping 61.5% of Canadian households bought at least some bird seed and spent the U.S equivalent of $800 million on it.
But is all this bird feeding good for the birds? How much do birds really rely on supplemental food provided by bird lovers? Some say as little as 10-25% of the daily food intake actually comes from bird feeders — but these are estimates, not actual measures. There are surprisingly few studies on the subject, but I’ll summarize some of the salient findings of the few studies I found.
1. Supplemental feeding in the winter promotes survival, especially of weaker individuals in the population.
This sounds like a good thing, but is it? One of the primary tenets of natural selection is the “struggle for survival”, in which only the most fit continue their genetic legacy. Weaker individuals are by definition less fit, more prone to disease and may, in fact, promote disease in an otherwise healthy population. So, really, not such a good thing.
2. Supplemental feeding promotes breeding success by advancing the date of the first clutch of eggs laid, and encouraging more birds to breed (provided there is space for them).
This also sounds like a good thing to promote. Birds supplemented by winter feeding have higher levels of fat supplies in the spring and can commence their reproductive cycle earlier and with more vigor. But, by doing so, they may actually get out of sync with the food supply on which the chicks depend for nourishment, and end up raising a clutch of weaker individuals — which would then be supplemented by backyard bird feeders, and so the circle goes round and round. In the U.K., researchers found that clutch sizes of the Blue Tit (a chickadee relative) were smaller and there was lower overall hatching success in populations that were supplemented with winter feed.
Increased numbers of nesting birds of a particular species also increases the competition for food, meaning everyone gets less of everything.
3. Supplemental feeding discourages migration and encourages northward expansion of some species’ ranges — which is great for us northern bird watchers, right?
This has been demonstrated for a few species, most notably the Northern Cardinal whose range keeps steadily expanding northward. But each morning I marvel that the little Yellow-bellied Sapsucker is still here in the backyard, pounding away at the suet, and I wonder if it eats anything besides suet. That can’t be a good diet.
I am not advocating here that we should stop feeding birds — that would really diminish the opportunities and enjoyment of winter photography around here, to say nothing of the enjoyment of just watching their daily activity. But I do think we should practice restraint on the quantity of low-quality seed distributed and promote healthy nutrition by supplying fresh, dry seed that perhaps has some vitamin supplement. Moldly, old seed is definitely bad for bird health, as are moldy, old feeders that have layers of who-knows-what between bird beaks and the fresh seed. So, with those cautions about the feed in mind — happy bird watching.