The Michigan and Wisconsin Department of Natural Resources experts remind bird-feeding enthusiasts that regularly cleaning and disinfecting the feeders are just as important as filling them - especially in efforts to prevent salmonellosis, a bacterial disease that kills many small birds.
Salmonellosis occurs when a food source is contaminated with fecal matter.
Since 1970, when this bacterial disease was first diagnosed in Michigan, die-offs around bird feeders have become more common and have been witnessed in many bird species throughout the world.
According to the DNR experts, bird watchers have reported finding dead birds around their feeders and, on occasion, having seen "sick-acting" birds.
Observable signs range from sudden death to a gradual decline of health over one to three days, accompanied by huddling of the birds, fluffed-up feathers, unsteadiness and shivering.
"We have received several calls from people who are finding dead goldfinches," said Brian Piccolo, a Michigan DNR wildlife biologist based in Roscommon. "The best thing you can do is remove and clean your bird feeder."
Piccolo said this bacterial disease is most common in house sparrows, pine siskins, American goldfinches and common redpolls, due to their habit of crowding onto the feeding area and remaining there until the food supply is exhausted - greatly increasing the number of bacteria a bird comes in contact with.
It also appears that these four species of birds are inherently more susceptible to the bacteria than other wild birds.
Bird experts advise that the most important control method for this bacterial disease is to disinfect all feeders and birdbaths weekly with a 10-percent bleach solution.
If the bacterial disease is suspected, bird feed should be removed from the area for two to four weeks to allow birds to disperse; this includes encouraging neighbors to also clean and remove feeders.
By allowing the birds to disperse, birds infected with the disease can separate from healthy birds.
Seed that is under the feeders and on the ground should also be raked or dug up in order to remove contaminated soil.
Fortunately, salmonellosis is not a cause of significant decline in the population of any wild bird species.
This disease is of interest to people feeding birds and the symptoms are sometimes mistakenly thought to be the result of poisoning.
"Feeding wildlife congregates them in a way that is not natural," explained Michigan DNR wildlife biologist/pathologist Tom Cooley. "Disease transmission is higher when wildlife is concentrated and in closer contact with each other."
Salmonellosis outbreaks around bird feeders generally subside with the milder weather of spring. During the spring and summer, when people typically do not feed birds, birds will forage individually while remaining in the same area.
Still, it is critically important to clean feeders and bird baths regularly to not only remove old seed and bird waste, but to also disinfect them with a weak bleach solution.
DNR experts offer the following tips:
- 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.
- 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.
- 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.
- 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.
- 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. Heat-resistant suet blocks are 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.