Wednesday, December 15th, 2004

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The Following Article is an excerpt from the Fall 2004 issue of "Shared Space", the newsletter of the PAWS Habitat Conservation Program. As bird feeding is a very common winter activity, I feel that it is important to disseminate this information to a broader audience. Please pass it along to anyone you know who maintains a backyard bird feeder.

Kevin Mack

Bird-friendly Bird Feeding
by Kevin Mack, PAWS Wildlife Naturalist

Backyard bird feeding is an extremely popular activity in the U.S. It is so popular in fact that it has become big business, and there are now entire retail chains dedicated to selling bird feeders, feed, bird baths, nest boxes, and other related items. Bird feeding is promoted as a benefit to humans in that it allows people to enjoy bird watching from the comfort of their own home. It is also promoted as a way to help the birds by providing them with a steady food source, especially during the lean fall and winter months. Since bird feeding is such a widespread practice, it is not entirely clear what the overall effects of the activity on bird movements, populations, and general behavior are. Because of this missing information, PAWS does not actively endorse the use of bird feeders as a way to help our avian neighbors. We do, however, provide information on safe bird feeding practices for those who choose to maintain bird feeders on their property.

During the fall and winter months, PAWS Wildlife Center frequently receives phone calls from homeowners who have spotted what appear to be sick songbirds hanging out around their feeders. They describe the bird as looking "puffed up", and generally the animals have been sitting in one place for a long period of time. Often, the callers have seen multiple birds behaving in this way over a period of days or weeks, and they may have even found a number of dead birds in their yard. Although the callers are aware that some disease process is at work in the birds that they are seeing, they are usually unaware of the role their bird feeders may be playing in facilitating the spread of disease.


Feeders provide close viewing opportunities, but they may also hold dangers for birds.

Bird feeders tend to concentrate many individual birds, and many different species in a small area. Actually, this is part of the appeal of bird feeders- the ability to see many different species from your living room window. And it's not entirely unnatural that birds should gather in large numbers since most of the birds that visit feeders in large groups are flock feeders to begin with. But there is one crucial difference between a flock of birds foraging together naturally, and a flock that is frequenting a feeder. With natural foraging, feeding in a particular area will diminish as the available food resources are depleted. This means that an area with abundant food may see a high concentration of birds, but only for a limited period of time. Eventually, the food is gone and the birds move elsewhere. With an artificial food source such as a feeder, the food supply is constantly being replenished, so a high concentration of birds is present for an extended period of time. If there are one or two sick birds among the flocks that visit a feeder, they can contaminate the feeder and expose dozens of subsequent visitors to their illness.

There are several different illnesses that are commonly associated with bird feeders. The most common is Salmonellosis. Salmonellosis is the general term for any disease caused by an infection of Salmonella bacteria. You may be familiar with Salmonella, as it is also known to cause infections in humans, and is often contracted from improperly cooked food. In birds, Salmonella spreads throughout the body and may cause abscesses in the lining of the esophagus and crop. Infected birds shed the bacteria in their feces, and if they are frequenting a bird feeder, the surface of the feeder or the food itself is likely to become contaminated with their feces. In this way, the feeder becomes a vector for the disease, spreading it to other birds that come to feed. Since humans, dogs, and cats may also contract Salmonellosis, an infected feeder may also become a hazard to the property owner and their pets.

In addition to bacterial infections, there are a few other diseases that have the potential to be spread at bird feeders. Trichomoniasis is a disease that is caused by a group of parasitic protozoans, the trichomonads. Birds infected with these single-celled organisms often develop sores and thick plaques in the mouth and throat. They have difficulty swallowing, and often drop food or water as they attempt to ingest it. Other birds then eat the food or drink the water and become infected.

Avian Pox is a virus that may potentially be spread at a bird feeder. A bird infected with the pox virus may exhibit warty growths on the face, wings, legs, or feet. The virus is spread by direct contact with an infected bird, or by picking up shed viruses on contaminated food or feeders.

Cedar Waxwing

Landscaping for wildlife may help you attract a wider variety of species, including those that do not generally frequent bird feeders.

Birds may also pick up a fungal infection such as Aspergillosis at a bird feeder. The Aspergillus fungus often grows on damp feed and in the debris beneath feeders. Birds become infected when they inhale the spores, and they may develop serious respiratory difficulties, including bronchitis and pneumonia, as a result.

Although bird feeders can present health risks to birds, there are several steps you can take to help to minimize the possibility that your feeders will become a vector for disease. First and foremost, you need to keep your feeders clean. Feeders should be disinfected at least once or twice a month, but weekly is even better. Discard all uneaten food, scrub the feeder thoroughly, and then disinfect it with a 10% bleach solution. Rinse the feeder and allow it to dry completely before using it again. Plastic and metal feeders are preferable as they can be more thoroughly cleaned than wooden feeders. Also, be sure to wear gloves whenever you are handling your feeders to decrease your own risk of exposure to potential disease.

In addition to cleaning your feeders, be sure to clean up all spilled seed and feces around your feeders. Ground feeding birds and rodents may become infected by contaminated seed on the ground. Your pets may also come into contact with contaminated feed or feces if the area under a feeder is not kept clean. It is also a good idea to move a feeder to a new location every time you clean it to lessen the chance that contamination will build up on the ground below it.

Since the food itself can be a vector for disease, be sure that you are only offering fresh, high quality food. Large capacity feeders may be convenient in that you have to refill them less often, but they increase the chances that the food will become damp and/or contaminated. Discard any food that becomes damp and/or moldy, and disinfect the feeder or container that held it.

If you do spot birds on your property that appear ill, contact PAWS at 425-787-2500 ext. 854 for instruction.

As you can see, the use of bird feeders to attract birds to your yard may have drawbacks. In addition to the disease potential, feeders may provide an easy opportunity for neighborhood cats to kill birds, and they may also attract mice and rats. Again, it's hard to know if the benefit of a steady food supply for the birds outweighs all of these other potential risks. There is, however, another way you can attract birds to your yard that avoids the potential pitfalls of feeders.

By landscaping for wildlife you can change your entire property into a strong bird attractant. Many people have told me that they maintain bird feeders as a response to habitat loss, but a feeding station is no real substitute for habitat. Altering your property to provide for the needs of birds and other wildlife will help to give them back some of what they have lost. The animals may be more difficult to observe than they would be at a feeder, but you will likely draw a greater variety, and you may even find that birds are more fun to watch when they are exhibiting their natural foraging behavior. Feeders may be beneficial to birds as a food source during lean times, but in the long term, only appropriate habitat will ensure that these animals will continue to thrive. Landscaping for wildlife truly can be considered "bird-friendly" bird feeding.

Wildlife Release tally: November 17th to November 30th, 2004

2 Steller's Jay
1 Rock Pigeon
1 Band-tailed Pigeon
1 Canada Goose
1 Varied Thrush

Wildlife Release tally: 2004
1074 animals

All rights reserved. 2004 Progressive Animal Welfare Society