week of  2/13/02
 
 
 


The Naturalist's Corner
By Don Hendershot
As the snowfall picked up last Tuesday morning, so did the traffic at my feeders. Fourteen species were taking advantage of the convenient smorgasbord. They included one mammal, a red squirrel, and 13 different species of birds: mourning dove, blue jay, northern cardinal, song sparrow, white-throated sparrow, dark-eyed junco, Carolina chickadee, tufted titmouse, white-breasted nuthatch, red-bellied woodpecker, pine siskin, American goldfinch and evening grosbeak.

While there may be some altruistic warm and fuzzy feelings garnered from providing feed for wild birds during periods of harsh winter weather, make no mistake: the scattering of this food is more about nourishing the human soul than sustaining these feathery portals to nature. We feed birds because we enjoy it. It connects us to things wild. A connection harder and harder to come by in this age of sprawl and development.

This is not to say wild birds derive no benefit from easily accessible food during particularly severe weather, but biologists will tell you that adequate shelter is far more critical than supplemental food. During two winters of blizzards from 1976 to 1978, the Wisconsin Division of Wildlife received reports that retailers were selling poisoned bird feed. People were finding dead birds at their full feeders. Tests showed the feed was not toxic. The problem was a lack of shelter. Without protection from the blizzards, birds could not eat enough to offset the cold. Improving backyard habitats for birds by adding brush piles and planting native shrubs and trees with dense evergreen foliage will do more to aid the overall well being of local avian populations than feeding.

There is a definite need for more research regarding the effects of backyard feeding on wild bird distribution and population, but the modest research done to date points to little impact, either positive or negative. There is some data that suggests a northward advancement of northern cardinal, tufted titmouse and mourning dove, and an east to west advancement of the eastern house finch that might be influenced by backyard feeding. But most ornithologists agree that if all feeding stopped tomorrow, there would be little change in population numbers or trends.

Most of the negative impacts from feeding are local in nature. As I said earlier, we feed birds for our enjoyment. To enjoy, we need to see. We generally place feeders near large windows. Not surprisingly, an Audubon report lists the greatest cause of avian mortality associated with feeding to be window-collisions. A “Journal of Field Ornithology” article puts the number of avian deaths caused by window-collisions at more than 97 million.

Predators pose another problem at feeding stations. Outdoor, domestic cats are the biggest problem, accounting for about 30 percent of the mortality at feeders. Putting bells on their collars does not prevent them from preying on birds.

Cooper’s hawks and sharp-shinned hawks, while more natural in an ecological sense, can also cause problems at feeders. Besides the prey, these hawks and/or cats catch, startled birds are more apt to fly into windows.

One negative impact from feeding that can grow from local to regional or greater in distribution is the spread of disease. Mycoplasmosis is a disease that causes conjunctivitis (infection of the eye membranes) in songbirds. Eastern house finches appear particularly susceptible to conjunctivitis. The disease first appeared in eastern house finches in the winter of 1993-94 in Virginia and Maryland. It has now been reported throughout the range of the eastern house finch and has been documented in populations of American goldfinches, purple finches, evening grosbeaks and pine grosbeaks. This disease is spread by contact, and crowded feeders are believed to contribute to its spread. In recent years, outbreaks of salmonella have also been recorded among house finches and other feeder birds.

The problems associated with feeding birds are created by humans and to a large extent can be greatly minimized by humans. Window collisions are caused because birds see the reflection of their habitat — trees, shrubs and sky — and cannot distinguish between the reflection and the real thing and fly into the window pane.

Window collisions can be eliminated by eliminating the reflection. There are films and treatments that can be applied to windows that allow homeowners to see out while getting rid of the reflection. However, these applications are not too aesthetically pleasing when viewing the windows from the yard.

The idea is to do as much as possible to break up the reflection. One of those little falcon silhouettes is not going to do the trick. Several silhouettes or decals six to 12 inches apart might do the trick, but they would block most of the view.

Hanging mobiles, wind chimes, stained glass and/or colored ribbons outside windows can usually be done in an effective and tasteful manner. Another suggestion is to keep feeding stations within a couple of yards of the windows. This way startled birds can’t build up enough momentum to seriously injure themselves.

Most disease problems can be alleviated by keeping feeders and their surrounding areas clean. Washing feeders a couple of times a year with a bleach-water solution (one part bleach to nine parts water) is usually sufficient. The ground under feeders should be raked when discarded seeds and droppings begin to build up.

Keeping your cats indoors not only protects birds but keeps pets healthier and safer also. If the problem is cats you don’t have control over, be sure your feeders are in the open and high enough and far enough from trees or railings that cats can’t leap to them.

If accipiters like Cooper’s hawks and sharp-shins become a constant nuisance simply quit feeding for a few days. When the hawks can no longer find easy pickings, they will resume their normal hunting routines.

And don’t fear you are forsaking the birds if your feeders remain empty for prolonged periods. Studies show that even where feeders are common they account for only about 20 percent of a bird’s diet. It’s like that donut you have at 10 a.m.; you can live without it.

By feeding wild birds, we are manipulating them for our enjoyment. The least we can do is to insure we do as little harm as possible.

(Don Hendershot can be reached at don@smokymountainnews.com)