Fall 2005

Table of Contents

Is Backyard Bird Feeding Helping or Hurting?

Every so often we’ve all heard the horror stories of diseases spread by and among birds at backyard feeders.

And once in a while those of us who stock feeders through the winter wonder if those fluffed-up balls of feathers braving the conditions outside our windows wouldn’t be better off flying south.

Is backyard bird feeding helping or hurting our feathered friends?

There’s no question that you can do more harm than good if dirty feeding stations end up spreading diseases through your local bird population. And it has been documented that feeding “shortstops” or causes some birds to discontinue their migration, perhaps to their detriment.

We don’t really know all the effects of backyard bird feeding. It might be part of the reduction in plant pollination, at least by hummingbirds coming to nectar feeders. It might be reducing native seed dispersal or consumption of insect pests. It might be creating an overpopulation of seed-eating birds, causing depletion of natural habitat.

It might be less nutritious for birds to eat more seeds and less insects and in turn they might be producing fewer viable young. Attracting birds to urban areas might expose them to more pesticides, more predation (especially by domestic cats), and more window collisions.

There’s lots of disagreements and conflicting conclusions and opinions among researchers on any and all of these possibilities.

But there are some things we DO know, and we can do something about.

Spreading diseases
Bird diseases aren't necessarily caused by humans feeding birds. Disease is part of a bird's natural world. But when you invite birds to dinner at your home, you want to be sure to avoid or minimize the potential for spreading disease.

The four main diseases observed in Washington are salmonellosis, avian pox, trichomaniasis, and aspergillosis.

Salmonellosis is a form of avian disease from the bacteria Salmonella. This is probably the most common disease at bird feeders in Washington. It frequently afflicts the more colonial, flocking species like pine siskins, evening grosbeaks, house finches and sometimes crossbills. The disease is spread by birds’ fecal droppings and by bird-to-bird contact.

The first indication of salmonellosis is often a very "tame" bird on your feeder or around your house. The afflicted birds become very lethargic and are easy to approach and even pick up. There is very little you can do to treat the birds at this point.

Avian Pox is a viral disease that causes wartlike growths on birds’ faces, legs, wings and feet. The virus is spread by direct contact with infected birds, ingestion of food and water contaminated by sick birds, or contact with contaminated surfaces such as at feeders, birdbaths, and perches. Insects, especially mosquitoes, also carry the disease from one bird to another.

Trichomaniasis is a disease caused by small parasites that can affect a wide variety of animals, including humans. The mourning dove and band-tailed pigeon seem to be particularly susceptible. The disease causes sores in their mouths and throats, and results in death from starvation or dehydration.

Aspergillosis is a disease caused by a fungal mold that grows on damp feed or soil in or around the feeder. Birds inhale the fungal spores and the disease spreads throughout their lungs and air sacs, causing bronchitis and pneumonia.

If you see evidence of any of these diseases at your feeders, the most important thing you can and should do immediately is remove your feeders and/or clean them with a bactericide, like a ten percent chlorine or bleach solution. If you leave the feeders up, clean them weekly.

One of the better ways to address the potential disease problem during the wet months of the year is to switch to using only tube feeders rather than the house-like or platform feeders. Feeders that have more flat surfaces collect more droppings, fungus, and other dirt that may spread disease.

There are other ways to minimize chances of a disease outbreak at your feeders.

Give birds space - Spread more feeders over a greater space. Crowding is a key factor in spreading disease because birds have more direct contact, jostle each other, and are stressed and thus more vulnerable. Use smaller feeders that allow only a couple of birds to feed at a time.

Clean up wastes - Regularly rake the area underneath feeders to remove droppings and old, moldy seed. Mount feeders over a surface that can be swept easily. Move feeders around periodically to keep droppings from collecting.

Keep feeders clean and dry - Clean and disinfect feeders regularly, using one part chlorine or bleach to ten parts tepid water. Soak feeders and all parts for at least 10 minutes. Scrub, thoroughly rinse, and dry completely before re-using. Repeat every couple of weeks or more often if you notice sick birds. Avoid using wood feeders because they’re difficult to keep clean. Make sure feeders allow rainwater to drain easily.

Use good feed - If any feed smells or looks musty or moldy, don’t use it. Disinfect storage containers and scoops used with spoiled feed before replacing with fresh, clean, dry feed. Also, avoid seed mixes, especially those with mostly milo or millet; most birds will scatter mixes for more preferred seed and the waste on the ground can become wet and moldy.

Changing Migration Patterns
As for the idea that winter feeding lures migrants into sticking around this far north longer than they should, consider the species you’re attracting.

Hummingbirds in particular may be at risk if nectar continues to be available in feeders. Like other birds, hummers are probably triggered to migrate by the changing “photo period” or hours of light in a day. Even if you continue to provide sugar-water, most of them just stop coming to your feeders because they’re heading south.

But food availability can be another key migration trigger. In most parts of Washington, freezing nights in autumn will force you to cut off the sugar-water supply. But in some of our milder areas, nectar can and is provided without freezing most of the year. In these situations there have been cases of humming birds staying around so long that when the inevitable cold snap comes, they freeze to death.

For our hummers, it’s probably best to stop supplying sugar-water by early autumn, wish them well in their travels south, and welcome them back again in spring with another season of feeding.

Other species that are probably better off without our winter feeding help are waterfowl. It’s not that ducks and geese might freeze to death if we entice them to stay around too long. It’s more a matter of creating artificially high, and possibly unhealthy, populations of them.

An obvious example is the horde of urban geese and ducks fouling the sidewalks, lawns, parks, and lakes of many Washington cities and suburbs. Once-migrant Canada geese are becoming year-round residents, attracted to artificial concentrations of food like lawns, as well as direct human handouts.

These kinds of migratory changes in songbirds are harder to detect. Most of the species that you see at your feeder have always been year-round residents, like chickadees. But there may be some that once headed south every winter, and over many decades of backyard feeder help, have adapted to staying around longer or even year-round. Mourning doves may be an example in the west. In the east, cardinals and some woodpeckers appear to have expanded their ranges over time due to feeders.

Range Expansion
Inadvertent supplemental feeding has increased some species populations. Red-winged blackbirds originally only inhabited wetlands, but now they feed on leftover corn, wheat, and other grains on today’s large farms. There’s speculation that supplemental feeding may explain the explosive range expansion of the house finch, a western North American species that was introduced in New York City in 1940 and now inhabits backyards all the way to the Mississippi.

Dependency
An important thing to remember about backyard bird feeding is that birds rarely if ever depend on you completely. Most spend only part of their time at feeders and continue to forage naturally throughout most of the season. Studies of black-capped chickadees, Australian magpie, for example, have found no evidence that feeding promotes dependency on one food source.

In nature, birds rarely “put all their eggs in one basket” when it comes to food sources because a snow storm or fire can wipe out any one source instantly. So you really don’t have to worry if the feeders go empty while you’re out of town over the holidays.

Increased Risk of Predation
There is much disagreement on this subject in both belief and research conclusions. Even Erica Dunn and Diane Tessaglia of Cornell University’s Project FeederWatch, proponents of bird feeding, are unable to deduce conclusively that bird feeding is safe from increased predation. They stated that “Homes without any bird feeders at all will suffer a far lower rate of predation than reported in this study; nonetheless, we doubt that bird feeding causes higher predation mortality than would be found in more natural settings.” They were able to conclude that exposure of birds to predation by small hawks and domestic cats varied with habitat circumstances in the yard: it is better to have a specialized feeding system, such as niger tube feeders and separate suet feeders, with no ground feeding.

Whatever the possibilities, we have to think of bird feeding in collective terms. Hundreds of millions of people feed birds in this country, which means we have a much, much larger effect on bird populations than what is just occurring in our own backyard.

Backyard bird feeding IS enjoyable, educational, and possibly even helpful to some birds. Resident Black-capped chickadees in Wisconsin, for one, were shown to survive winter in greater numbers and better condition when using feeders regularly.

One thing is for sure – Bird feeding is NOT a substitute for habitat protection and natural foraging habitat for birds. It is not a quick and dirty solution to habitat destruction and declining populations. It is a recreation more than anything. Declining insect foragers such as the thrushes cannot be replaced by increasing numbers of seed-eaters such as house finches and house sparrows.

So what’s the ultimate answer to the bird feeding question?

Right now, we leave that up to you to decide if you would like to have feeders or not. But, if you choose to feed birds, practice “safe bird feeding”: keep feeders to a minimum, keep them clean, learn proper placement and landscaping techniques for surrounding your feeders, and understand the value of natural food and native vegetation.