Astrid Kasper DVM

Bird feeding adds so much to our enjoyment of nature as it draws these little feathered friends into the human environment where they can be observed at close proximity. There are certain responsibilities, however, which come with this privilege, in order to protect the health of our guests.

Birds are attracted by different kinds of foods, ranging from seeds, to nectar, mealworms or fruit, each with its specialized feeder. Consider which species are prevalent in your backyard and which ones you want to particularly attract, when buying a feeder. A well set table will attract crowds, thereby also increasing the chances of transmitting disease. Some birds live separately between mating seasons, establish their territory and do not appreciate intruders. By setting up more than one feeder, you will avoid crowding and reduce the stress levels of your birds, thereby contributing to their health.

Bird Feeder Hygiene

Clean and disinfect your bird feeder whenever you refill it, ideally once a week. Liquid chlorine household bleach makes a perfect, cheap disinfectant by mixing one part bleach with nine parts water, which gives a 10 % solution. After a good scrub with soap the bird feeder needs to be rinsed or even better soaked for 10 minutes in this solution. If the feeder is too large to be submerged, fill your disinfectant solution into a spray bottle and spray it well without overlooking hidden corners. The solution needs to be made up fresh each time because it looses its strength after 24 hours. Then rinse your bird feeder and let it dry thoroughly, especially wooden structures. Finally, replenish the container with the seeds of your choice according to the species you want to attract.

Store food in rodent and water proof containers in a cool area. Discard any food that smells musty, is wet, looks moldy or has fungus growing on it. Contaminated storage containers and scoops that held spoiled food need to be cleaned as well.

Birds are messy eaters but it is our responsibility to clean the feeder area of wasted food and droppings, which make a perfect sources of infection. If the ground beneath your feeder is smooth, a broom and shovel will do the job otherwise I recommend a heavy duty vacuum cleaner; in either case, hose down the area generously. If you can without causing local damage to plants or house, apply the rest of your 10 % bleach solution and disinfect the area.

Nectar feeders should be thoroughly cleaned and bleached once a week and refilled on a regular base. Bird bath areas with standing water need to be bleached weekly and should be emptied and refilled with fresh water on a daily basis. Allow ample space between the bird bath and the feeder area.

How to Recognize a Sick Bird

Sick birds do show up at bird feeders from time to time where they endanger other birds as well. In order to recognize a sick bird, you have to be familiar with the birds in your neighborhood, know their typical activity levels well, and be observant because birds depend on hiding any symptoms of disease, in order to survive. Otherwise they would send a signal to predators and could easily become their next meal.

In advanced states of disease, you will find birds to be less alert active, fluffed up, hardly eating but still reluctant to leave. Chronically ill birds have poorly maintained, dull feathers as they cannot keep up with the preening process. Injuries to the wing and feet are obvious and usually easy to spot.

Sick or injured birds should be caught and brought to a rehabilitation center quickly. If no net is available, throw a light towel or a sheet over the bird to capture it. Place it in a brown paper shopping bag closed off with a clothes pin; transport the patient as fast as possible and without extra noise pollution (radio) to limit the stress level which is already high.

Some Common Diseases

Wartlike growths around the eyes, the beak or the feet often stem from Avian Pox a virus infection transmitted by direct contact with contaminated food or water and by insects, which may have been attracted by an open wound and body fluids. This virus affects all unfeathered skin areas, is usually aggravated by secondary bacterial infections and is an ubiquitous infection of wild birds ranging from sparrows to corvides, and raptors. Avian pox virus infections can remain latent for years in a flock and become reactivated by non-specific stress factors.

Trichomoniasis, a protozoan infection, causes inflammation in the mucosa of the upper digestive tract and mouth resulting in dysphagia or vomiting. Birds may develop large, up to golf ball size tumor-like growths in the crop region which are visible from a distance. Without proper treatment, such a bird will starve to death because the esophagus becomes totally obstructed. Mourning doves, pigeons and raptors are especially affected.

Probably the most common bacterial infection is Salmonellosis, often passed on by already infected birds via fecal droppings that end up in the food. We can thus do much for prevention by proper hygienic measures. Salmonellosis has a high mortality rate. A few years ago it heavily affected the Pine Siskin population in the Northwest coastal areas. Avian species without ceca or with involuted ceca appear to be more susceptible to salmonella infections than birds with fully functioning ceca. Free-ranging birds can be subclinical carriers and serve as a reservoir. Salmonella infection can eventually induce septicemia and death. Recurrent infections usually result in progressive organ involvement; the CNS and joints are frequently end stage sites of infection.

Moist seeds and debris caught beneath feeders are a breeding ground for fungus. Fungi produce spores which not only survive dry conditions for a very long time, but easily get stirred up and inhaled by landing birds.

Aspergillosis is a fungal infection of the respiratory tract, an opportunistic ubiquitous pathogen. The avian respiratory system has six to nine air sacs (depending on species) which form an ideal breeding ground for fungus infections due to the constant warmth and moisture. The air sacs are not well supplied by blood vessels (as opposed to the lung) because they mainly serve as passage for the air and as weight reduction system. Therefore they are also not well accessible to a bird’s immune response and have a very poor prognosis.

Aspergillosis has an acute (within a week), subacute (weeks), and chronic (weeks or even months) disease progression. Predisposing factors for acquiring fungus infections include immune suppression (often caused by stress), malnutrition or poor husbandry practices (general hygienic factors and ventilation problems). In a hospital setting, prolonged treatment with antibiotics and/or corticosteroids due to a pre-existing disease will also enhance the chances of aspergillosis.

Summary

As you see, the main issue around bird feeders is contagion, either by direct or indirect contact with pathogens like bacteria, viruses, fungal spores or parasites. Proper hygiene and avoiding overcrowding will go a long way in keeping your birds healthy and enhance your bird watching pleasure.