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Wisconsin Natural Resources magazine

Wisconsin Natural Resources magazine

Clean feeders and birdbaths can limit the buildup and spread of disease where birds congregate. © Jarrod Erbe
Clean feeders and birdbaths can limit the buildup and spread of disease where birds congregate.

© Jarrod Erbe

February 2007

Keep neater feeders

A few simple steps can help keep songbirds healthy as they wing in for a little seed and conversation.

Erin S. Larson and
Simon R. Hollamby

Cold weather and snow cover lead songbirds to risk gathering at backyard feeders to supplement dwindling food supplies. Flocking birds keep a watchful eye for predators, but there are other potential killers lurking at the feeders – microbes!

Several diseases spread more readily as birds concentrate, defecate and have more beak to beak contact. One disease, avian salmonellosis, is caused by a variety of bacterial strains whose health effects can be moderated by a range of environmental and host factors. Infections can be transmitted in many ways which vary with the strain of salmonella and the feeding and behavioral pattern of the species.

Despite the widespread belief that birds are carriers of high levels of salmonella, surveys show that the prevalence of these bacteria in most wild bird populations is generally low. Most bird species rapidly eliminate salmonella from their intestinal tract. However, individual birds can excrete salmonella for weeks or months. These individual birds may remain lifelong carriers intermittently excreting bacteria into the environment. This can lead to persistent contamination of feeding sites during periods of greatest use, such as winter in Wisconsin.

Unfortunately, this parallels a period when songbirds are already under nutritional stress searching for adequate food supplies and are more vulnerable to disease. Outbreaks increase after birds ingest bird seeds, water or suet contaminated with the droppings of other highly stressed birds as they crowd around the feeders in cold weather. Young birds may be more susceptible because their immune systems are less well-developed than those of adult birds. There are no distinctive signs of salmonella in wild birds. You may notice a combination of several signs including ruffled feathers, lethargy, unsteadiness, rapid breathing and diarrhea. Often you won't see any unusual signs, yet the affected birds die very quickly.

Large scale die-offs of wild birds are usually isolated to songbirds at feeding stations and colonial nesting birds, such as gulls. Before the 1980s, large scale mortality of songbirds at feeders was rare. The increase in salmonella at bird feeding stations may be due to increased contact birds had with sources of environmental contamination like garbage, wastewater discharges from livestock and poultry operations, sewage, greater bird concentration, more feeding opportunities, and population changes in songbird species that are especially susceptible to salmonellosis.

Birds that feed around contaminated areas may become carriers and spread salmonella to other bird feeders, especially when maintenance and disinfection of the bird feeder is poor. Storing bird seed and beef suet in containers that are not rodent and insectproof can also be a source of salmonella at bird feeding stations.

Salmonella can potentially be contracted by humans through contaminated bird feeding stations. However, a much more common source of salmonella in people is food poisoning that brings on abdominal pain and diarrhea.

Follow a few simple guidelines to help protect yourself and the birds you are feeding from diseases such as salmonella:

  • Wear disposable gloves when you clean feeders, feeding areas and birdbaths.

  • Clean feeders and the area under them weekly. Rake spent seed and feces away from areas where seed may drop to the ground and attract birds. When cleaning feeders outside, wash them off using plastic buckets of hot, sudsy water with disinfectants. If it is really cold outside, clean off the feeders in a utility sink, not in the kitchen sink near food preparation areas. Do not use kitchen sponges or any other cleaning utensils or towels that might subsequently be used for food preparation. Clean feeders with disposable towels, wear disposable gloves and move soiled materials to the garbage immediately. Also wash your hands well and vigorously after cleaning feeders and birdbaths.

  • Disinfect feeders using a 10 percent bleach solution (nine parts water to one part bleach). If the feeder is small, soak the cleaned feeder in a pail of bleach solution for 10 minutes or more before thoroughly rinsing the feeder with fresh water. Let it air dry before refilling it with fresh seed. If the feeder is too large to submerge in water, clean it well, then fill a spray bottle with the disinfectant solution. Make sure to spray hidden corners! Make up fresh solution each time because it loses its strength after 24 hours.

    Wear eye protection as well to keep the bleach solution out of your eyes and off your skin.

    Platform feeders need more frequent cleaning than tube feeders because they hold feces and other excreted wastes. On the other hand, the deck or soil under tube feeders allow water and fungi to mix in with spilled seed on the ground. This mix may attract a whole different group of ground-feeding birds and mammals compounding contamination. Also inspect the feeder for sharp points and edges that might injure a bird. Small scratches and cuts allow bacteria and viruses to infect otherwise healthy birds.

    It is best to clean the feeders away from the immediate feeding area so the droppings you scrape off don't infect any seed on the ground under the feeder.

  • Dispose of seed hulls that collect under feeders. They make good mulch.

  • Consider moving feeders periodically to prevent buildup of waste underneath the feeder.

  • Keep seeds and other bird food dry and in sealed, watertight, animal-proof containers. Discard any food that gets wet or moldy.

  • Replace water in a birdbath every 2-3 days.

  • If sick or dead birds are observed at a feeder, take it down, discard all seed, and give everything a thorough cleaning. Wait at least a few weeks before setting up the feeder again to allow healthy birds time to disperse. This lessens the possibility of disease transmission. Report sick birds to local wildlife officials, many of whom monitor wildlife health.

  • Give seed feeders a good shake before refilling them to dislodge any compacted seed. Dump out and discard any wet clumps. Offer hulled sunflower hearts or bits when the weather is dry or put them in a tube feeder or hopper feeder. Wet weather causes hulled, oily seeds to spoil.

  • If you provide suet, reduce the amount you offer in hot weather. Suet turns rancid in heat and becomes unhealthy for birds. Runny suet can also stick to birds' feathers making them harder to keep clean. Homemade suet will keep longer if you render the fat first. Heat-resistant suet blocks are also available at pet supply and bird supply stores.

  • Don't use oil, petroleum jelly or similar greasy substances on feeder poles or wires to thwart squirrels, ants and other feeder raiders. It's impossible for birds to preen or wash off these greasy solutions from their feathers. Gooey feathers are useless for flight and insulation putting the birds at risk to predators, extreme weather and disease. To stop squirrels, consider pole-mounted baffles. Commercial ant guards are also available at stores, via mail-order and on the Internet.

  • Reduce window kills by placing feeders a safe distance away so birds don't see their reflections. If birds regularly strike a window pane, screens, netting and stencils can break up the reflection pattern. (See our April 2006 story Threshold of pane for more ideas).

Erin S. Larson and Simon R. Hollamby wrote this piece for DNR's Wildlife Health Team. Larson is now CWD Data Coordinator and veterinarian Hollamby currently lectures about wildlife and exotic animal medicine at the University of Edinburgh in Scotland.