Thursday, April 09, 2009

Sick siskins

We've gotten many reports of Pine Siskins this winter and early spring. The incredible irruption of these northern birds into southern territories is like none in recent years, and siskins are still here as of April 7.

But this big crowd of birds has brought with it a problem – aside from breaking our birdseed budgets with their gluttonous consumption. Siskins may be prone to disease.

Kathy Cory of South Salem, N.Y. tells us, “I noticed a lethargic siskin in the yard this morning, which perished soon after. That's the second dead one in the yard this week, and I remembered seeing another sickly one a few weeks ago.

“I have learned that they are very susceptible to salmonella, possibly from dirty bird feeders. Since all of us have had very busy bird feeders this winter, perhaps we need to be more diligent than usual about cleaning them. Could it be the feeders or is there another force at work out there?”

On the Connecticut bird hotline, sick siskins have been a hot topic.

Julie Keefer of Lyme said there were “a lot of reports of siskins dying in North Carolina this winter and I think it was pretty much a mystery as to why.” She wonders whether the ones succumbing here caught their fatal disease in the South – the ones we are seeing now may be migrating north and are not necessarily the same birds that were at our feeders in winter.

Paul Carrier, a Harwinton naturalist and wildlife artist who found dead siskins in his yard recently, said, “As we feed the birds from the same feeders continually in one spot all winter, it is not natural. The accumulation of husks and spillage under the feeders will eventually become a breeding ground for molds and disease, especially as it gets warmer. We all must clean up under the feeders as much as we can now that it’s warmer out.”

Paul added, “thistle is a very fast decomposing seed (husks), especially when wet. These I believe are the culprit to the sickness in these siskins, especially when they eat them from the ground. When it is cold, the seeds don't grow molds and such. But when wet and warm, they become instant breeding grounds for disaster!”

Cornell Lab of Ornithology’s Project Feeder Watch has been getting many similar reports. “As often happens in birds that feed and roost in tight flocks, there have been outbreaks of salmonella reported in some Pine Siskin flocks,” Cornell said. “Salmonellosis is caused by a bacteria... It is a common cause of mortality in feeder birds, but the symptoms are not always obvious. Sick birds may appear thin, fluffed up, and may have swollen eyelids. They are often lethargic and easy to approach. Some infected birds may show no outward symptoms but are carriers of the disease and can spread the infection to other birds.”

Salmonellosis is mainly transmitted by fecal contamination of food and water by sick birds, though it can also be transmitted by bird-to-bird contact, Cornell says. Occasionally, outbreaks cause “significant mortality.”

Cornell says, “Clean your feeders about once every two weeks, more often during times of heavy use. For best results wash your feeder thoroughly in soapy water, then soak or rinse it in a solution of one part bleach to nine parts water. Dry the feeder thoroughly before refilling.”

It adds, “Remember to rake the ground below your feeder to prevent accumulation of waste. Moldy or spoiled food is unhealthy, not only for birds but for your outside pets. Bird food scattered on the ground also can attract rodents. Consider moving your feeders periodically to limit the accumulation of waste.”

One hotline participant said sunflower chips, which siskins love, have the advantage of not having hulls to get moldy and diseased on the ground.

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