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Eye disease, nuts, and caching
Answers to readers' questions about House Finches, nut mixes, and caching
Contributed by Julie Craves
Published: October 21, 2011
What is the status of House Finch eye disease? — Marvin W. Rogers, Richardson, Texas
Around 1994, people in the eastern United States began noticing House Finches with crusty, runny, and swollen eyes. The condition is known as conjunctivitis. The strain of bacteria that causes it, Mycoplasm gallisepticum, had previously been known to infect only domestic poultry. The disease spread rapidly through the eastern finch population and was often fatal. It spread more slowly west of the Rocky Mountains.
Sometimes other finch species are infected, but because the eastern population of House Finches was derived from a small number of birds released in the 1940s and has low genetic diversity, it may be more susceptible to diseases. Curiously, two studies found the disease to be more severe in the left eye, but the reason is not known.
Now, mycoplasmal conjunctivitis seems to have reached a stable state, infecting about 5 to 10 percent of House Finches. Recent genetic studies indicate that the birds are evolving resistance to the disease through natural selection, so we may see further reduction in its impact. To help prevent the spread of this and other pathogens, it’s important to keep your feeders clean. Use a 10 percent bleach solution, and rinse and dry them thoroughly. Also, prevent the buildup of droppings and old seeds on the ground beneath your feeders.
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I feed nut mixes that sometimes contain a few cashews, Brazil nuts, and almonds. The birds eat everything but the almonds. Why? — Rob Rachlin, Greensboro, North Carolina
Almonds are sometimes included in suet mixes and pet parrot foods, so there isn’t any particular reason why birds shouldn’t eat them. Almonds contain small amounts of the toxin cyanide, and rare cases of poisoning of wild birds have been documented. But it’s much more common for birds to damage almond groves by eating the nutritious nuts.
I assume that if you are putting out mixed nuts they have been roasted for human consumption. They typically contain salt, which should not be fed to birds, and they may also have other preservatives or ingredients that birds shouldn’t eat. As a general rule, stick to feeding the birds in your yard fresh seed and other food items that you purchase at a reputable wild-bird-feeding store.
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Is information available before winter about whether there will be a fallout of winter finches at backyard feeders? — Rosemary Harris, Pickering, Ontario
Yes! Each fall, usually in late September, Canadian ornithologist Ron Pittaway publishes an eagerly anticipated winter-finch forecast. Ron assesses reports of tree cone, seed, and fruit crops across much of Canada. He uses the data to help predict whether the birds that feed on them will find enough food (in which case, they will stay north) or whether the crops won’t sustain their populations (which usually leads to significant southbound movements).
The species Ron focuses on are redpolls, crossbills, Pine and Evening Grosbeaks, Purple Finch, and Pine Siskin. Ron also discusses movements of Blue Jay, Red-breasted Nuthatch, and Bohemian Waxwing since they also come south depending on food sources. While the forecasts are most applicable to the northern and eastern United States and southern Canada, they also include information on how the birds might move across the continent.
Ron’s forecast for this winter was published September 23 and can be found online at www.ofo.ca, the website of the Ontario Field Ornithologists.
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What do chickadees do with all those seeds? — Gerry Whitley, Whitehorse, Yukon
Chickadees at feeding stations are busy birds. You may see them take a single seed (often a sunflower), fly a short distance, stand on it with one foot, crack it open with a blow of the bill, and consume it.
But chickadees — as well as jays, titmice, nuthatches, and woodpeckers — also hide seeds and other food items in cracks and crevices in tree bark, telephone or fence poles, home siding, or other places within their winter territories. This food storing is known as caching. Most birds carry one seed at a time, but you might see jays gobbling down dozens of seeds before flying off. They have a special throat pouch that enables them to hold a lot of seeds.
Chickadees and their relatives usually cache close to the food source and recover it within a week, while jays may cache over a wider area. If they are resident, they may not reclaim their food for many weeks.
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