SCOTT SHALAWAY The ups and downs of house finches

When I arrived here on the ridge back in 1985 and set up my first feeding station, the only red birds that came to the feeders were cardinals and a few winter purple finches. Within a few years, however, house finches became one of the more common feeder birds in my backyard. I suspect many eastern backyard birders can tell a similar tale.
The story behind the sudden eastern appearance of house finches is a lesson in how an introduced species can experience a population explosion. Until 1940 house finches lived strictly west of the Great Plains from Canada south into Mexico. In the late 1930s they became popular, though illegal, favorites of the pet bird trade. In 1940 some California cage bird dealers shipped some east and sold them to New York pet dealers as "Hollywood finches."
Agents moved in
Wildlife agents quickly moved in to shut down the operation, but the bird dealers, not wanting to be caught red-handed, released the evidence. Within three years house finches were nesting and reproducing on Long Island.
The rest is history. In less than 50 years house finches colonized the east - from New England to Georgia and west to the Mississippi River. They adapted readily to urban environments, nesting in tree cavities, bird houses, and dense vines and shrubbery. I've found house finch nests on ivy-covered walls, in potted plants on porches, and in rolled up awnings. If you have reddish finches nesting in these situations, they are house finches, not purple finches.
These two confusing red finches are not difficult to distinguish. Male house finches have red foreheads, throats, eyebrows, and rumps. Their bellies are white with heavy brown streaking on the sides. Male purple finches are chunkier, more reddish overall, and lack the brown belly markings.
Finch description
Female purple and house finches are nondescript streaky brown birds. Facial markings distinguish this confusing pair. Female house finches have a plain brown head. The brown heads of female purple finches are set off by a bold white eyebrow stripe.
Another way to recognize house finches is by the crusty lesions that sometimes cover their eyes. Since 1994, eastern house finches have been plagued by a bacterium (Mycoplasma gallisepticum) that infects their eyes. Ornithologists, pathologists, and veterinarians, intrigued by its rapid spread, have tracked the disease ever since. It causes an eye infection that results in conjunctivitis that ranges from mild to severe. Sometimes liquid oozes from the eyes; in severe cases the eyes swell shut. Many house finches, blinded by swollen eyelids, succumb to predators and starvation.
The bacterium itself is seldom fatal and runs its course in about 10 days, but few infected finches can elude predators and find food long enough to survive. As a result the eastern house finch population peaked eight or nine years ago. Back in the early 1990s, they were the most common bird in my backyard; today my house finch population is down noticeably. I'm curious if any readers have noticed a similar trend in house finch numbers.
Use same nest
House finches raise as many as three broods per year, each containing up to five chicks. Sometimes they use the same nest repeatedly, especially on protected porches.
The expansion of house finches (or linnets, as they are sometimes called) throughout the east has had both positive and negative consequences. The good news is that house finches seem to displace house sparrows in areas where both occur. In many areas, the number of house sparrows seems to decline as house finches increase.
On the down side, many people object to having their feeders dominated by house finches. They are aggressive and sometime drive off smaller species. Given the choice, though, I'd rather have too many house finches than too many house sparrows.
To discourage house finches, try using an "upside down" finch tube. The small seed ports on this feeder are below, rather than above, the perches. This requires birds to hang upside down to feed. Goldfinches and pine siskins are quite acrobatic and readily use this feeder, but house finches prefer to remain upright while feeding.
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