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Birds and humans are both susceptible to epidemics made worse by close proximity

Photo by Wileydoc/Pixabay — Pine siskins flock to a feeder. Many birds that congregate in large flocks at feeders and bird baths are susceptible to contagious diseases, just like humans.

By Bryan Stevens

I wrote several columns about an abundance of finches earlier this winter and late last fall. Some of these flocks, consisting of such species as purple finches, pine siskins and evening grosbeaks, have persisted. Unfortunately, there is sometimes too much of a good thing as a Facebook post from Carolyn Dover Norman reminded me.

Carolyn posted on my Facebook page to share some concerns about an ongoing epidemic affecting some of our favorite feeder visitors.

“I read your article on the internet about the pine siskins and enjoyed it very much,” she wrote. “I live in Texas and have thousands ( it seems) of siskins in our trees this winter. Yes, they are a friendly bird and two allowed me to pick them up off the ground, but now I learn that they are sick with salmonella.” Carolyn said the infected birds don’t appear to be well and are extra tame. She wondered if I had ever heard of this species being more susceptible to this disease.

“I am having to remove and bleach all my feeders and take precautions,” she added.

Regrettably, I informed her that I have heard of outbreaks of various diseases that can affect different birds. Carolyn is to be commended for taking immediate action. She removed her feeders and disinfected them. By taking those steps, she could cautiously resume feeding the birds, although some careful monitoring of the flocks would seem to be in order.

Back in the 1990s, house finches were decimated by mycoplasmal conjunctivitis. Humans can get infected with conjunctivitis, which is commonly called “pink eye.” According to the Project FeederWatch website, infected finches have red, swollen, runny or crusty eyes. In extreme cases the eyes become swollen shut and the bird becomes blind. Observers might find an infected bird sitting quietly while clumsily scratching an eye against its foot or a perch. While some infected birds recover, many die from starvation, exposure or predation. Since the early outbreaks, the disease has affected several other wild bird species, including American goldfinch, evening grosbeak and purple finch.

I recall seeing both house finches and pine siskins suffering from this disease. I haven’t seen it as often in recent years, which is a relief.

Salmonella is another disease that can affect birds. As most people know, salmonella can also have serious consequences for human health. Finches, especially in the West Coast states of Oregon and California, have been hard hit by salmonella in recent months.

“Salmonellosis occurs periodically in pine siskins in some winters throughout their range. When large numbers of pine siskins congregate, the disease can spread rapidly causing high mortality. Most birds die within 24 hours of infection,” said California Department of Fish and Wildlife Senior Environmental Scientist Krysta Rogers, an avian disease specialist.

Birds become infected with salmonella when they ingest food, water or come into contact with objects, such as bird feeders, perches or soil, contaminated with feces from an infected bird. Sick birds often appear weak, have labored breathing, and may sit for prolonged periods with fluffed or ruffled feathers. Salmonellosis is almost exclusively reported from locations with bird feeders where birds congregate. Rogers advised that residents can help reduce disease transmission by removing bird feeders and bird baths. Allowing birds to feed on natural seeds rather than at bird feeders reduces contact between birds and helps slow spread of the disease. Some of the flocks of finches have been exceptionally large this winter, which is why it’s a good idea to closely monitor the birds at your feeders. At the first sign of illness, take steps to disinfect feeders. It’s a good idea to clean feeders on a regular basis. A spray with a weak bleach water solution followed by a few swipes with a clean towel can help. Once an outbreak is evident, however, the best course would be to stop feeding birds for a short period.

Songbirds aren’t the only birds affected by disease outbreaks. Waterfowl are often vulnerable. Like finches, many species of ducks and geese also form large flocks. Some of the diseases that can run rampant in waterfowl populations include avian influenza, avian cholera and avian botulism. According to the Ducks Unlimited website, major avian botulism outbreaks have been reported throughout North America for more than a century. In 1910, avian botulism resulted in the deaths of millions of waterfowl in California and Utah, and another incident in 1952 killed an estimate 4 million to 5 million waterfowl across the western United States.

In 1999, the West Nile virus, a mosquito-borne disease, arrived in the United States. This disease is typically a mild nuisance for most infected people, but in some circumstances the virus can be lethal. The virus, which first appeared in the United States in 1999 after being discovered in 1937 in the African nation of Uguanda, also didn’t confine itself to the human population. Soon after its arrival in the United States, the virus began decimating American crows. Two decades later, experts have been able to study the consequences of West Nile virus on both humans and wild birds.

According to an article by Hugh Powell published Oct. 15, 2010, on the All About Birds website, the disease afflicted crows more than any other bird species. “West Nile virus hit American crows particularly hard,” Powell wrote. “When the disease first appeared in New York City, in summer 1999, nearly 5,500 crows died in four months. Tests suggested the disease was 100-percent fatal to crows.” Many other species, from jays and magpies to gulls and chickadees, also proved susceptible, according to the All About Birds article.

Millions of birds died as West Nile swept across the continent in just five years. An interesting thing happened as the virus spread across the country. As viral diseases often tend to do, West Nile apparently became less virulent. The American crow population did hit frightening lows, but the species appears to have managed to rebound.

Where’s the silver lining in regard to all these stories? Here is a sliver of light through the dark clouds. Birds are resilient, just like humans. They can usually overcome anything nature might throw at them.

Keep feeding the birds, but play the diligent host. Put out only the amount of seed that visiting birds can eat in a single day. Monitor the flocks for any sign of illness and respond quickly if such signs are detected. Keep feeding the birds, but be safe and attentive while doing so.