It took house finches almost 43 years to make it from Jones Beach, Long Island, where birders identified the first wild eastern house finches, to our mountaintop in central Pennsylvania, even though they had been frequenting bird feeders in nearby valleys for seven years.
I know the exact date the first house finches appeared at our feeders–December 30, 1983. That was when I noticed a drab, brown-striped female eating by herself. A few seconds later, she was joined by a flashy male house finch. By April we had two pairs nesting in our yard.
We took them for granted back in the 1980s and early 1990s. As many as 75 mobbed our feeders during the winter, and a pair or two were always courting by late February. Most people dismissed them as just another invasive species like European starlings and house sparrows. Yet unlike those European immigrants, house finches are native Americans.
They originated in western North America, ranging from south central British Columbia to Oaxaca, Mexico, hence their scientific name Carpodacus mexicanus, which means “fruit biter of Mexico.” They especially favored the valleys of the Pacific slope of central and southern California. Once inhabitants of undisturbed wild places, they easily adjusted to our changes in the landscape and have subsequently thrived in our cities, suburbs, and farms, building their nests in a variety of places such as in yard trees, on ledges, in ivy on buildings, on street lamps, and in hanging planters.
Because these western house finches were known for their “rollicking, warbling” songs and the brown-streaked males for their colorful bright red or orange breasts and rumps, they were illegally captured, caged, and shipped to the eastern United States where they were sold as “Hollywood” finches in New York. When United States Fish and Wildlife Service agents moved to stop the trade, those dealers who possessed house finches quickly released them on Long Island to avoid arrest.
Although house finches took ten years to spread into nearby Connecticut and New Jersey, by 1980 house finches ranged as far north as southern Maine, west to southern Michigan and western Illinois, and south to Georgia, Alabama, and Mississippi. They weren’t quite the same bird though. Some eastern house finches learned to migrate and, as a result, their wing structure differs slightly from their western counterparts that never migrate.
Their songs have also changed. Male house finches in the eastern United States have local dialects, unlike those in the West. On the other hand, western house finches have far more diverse songs than those in the East.
The songs are sung almost year around, mostly by males, although occasionally females sing too. Males seem to sing to attract females, to show aggression to other house finches, and even for their own pleasure. Because there are many more males than females, competition for females in winter flocks, where they pair up, is fierce.
Most pairs are faithful through the nesting season, even though some occasionally switch mates. Others stay together and nest in subsequent years. Such pairs breed earlier and are more attentive to each other. The males more carefully tend the females as they sit on eggs, and the females are more likely to follow the males during nest-vicinity fights than those of later, presumably novice breeding pairs.
After the males’ frequent performance of their “butterfly flight” in which they slowly climb skyward and then glide back to a perch while singing loudly, pairs begin billing and then courtship feeding. That leads to nest-building, mostly by the female, and copulation. The male also fiercely guards the female during this period and through egg-laying.
House finches build their nests from mid-to-late March and lay between four and five eggs. In most places they have two or three nestings by late July. The females incubate the eggs from thirteen to seventeen days, depending on how cold the weather is, and after the eggs hatch, the parents feed the nestlings plant food which they regurgitate from their crops. The young fledge anywhere from twelve to nineteen days.
As with other invasive species, house finch numbers exploded in the eastern United States. They became the most common backyard bird in the country, pushing their closest relatives, purple finches (C. purpureus), as well as American goldfinches, from feeders. By 1991 estimates of individual house finches in North America ranged from 267,720,000 to 1,440,720,000.
Then, in 1994, disaster struck. In February Maryland feeder watchers noticed house finches with red, swollen, runny and crusty eyes. Scientists quickly determined that they had a respiratory infection, which they called conjunctivitis, which was caused by the bacterium Mycoplasma gallisepticum. A common disease in domestic turkeys and chickens, it had never before struck songbirds. Within ten months the house finch disease had spread from eastern Ontario to southern Virginia. Two and a half years later, folks across eastern North America had reported the disease at their feeders.
As a veteran participant in Cornell University’s Laboratory of Ornithology’s Project FeederWatch, that began in 1988, I was asked, along with the thousands of others in the program, to join their House Finch Disease Study. After two years of seeing no signs of disease in my flock, I withdrew from the study. But I continued my participation in Project FeederWatch. Through 1996-97, my house finch numbers remained in the sixty range. Then they started to fall. Still, I saw no sign of the disease. By 2001, my average flock size was three. That was the year when Cornell reported that house finch numbers had dropped a whopping sixty percent.
Conjunctivitis usually didn’t kill house finches outright, but they were essentially blind and couldn’t see to eat or evade predators. So they died from starvation, exposure, or predation.
House finches had long since ceased breeding here, and last winter, for the first time, not one house finch came to my feeders. At the same time, our American goldfinch flock rose to seventy-five. We also saw more purple finches in the late fall.
I wondered if others in Pennsylvania had had a similar experience, but of the fourteen people across the state who answered my query on the Pennsylvania Bird listserv, only one person reported no house finches. Almost everyone else had low numbers–6 to 8–except for Philadelphia, suburban Harrisburg, Quakertown, and Nazareth, Northampton County where numbers ranged as high as 25. Many folks recorded eye disease in their flocks, and two observers saw it in goldfinches and purple finches too.
Joyce and Phil Schaff of Chambersburg reported 9 purple finches, two of which had the disease, dozens of goldfinches, and only 5 to 6 house finches. Two of their house finches had conjunctivitis. Stan Kotala, who lives at the other end of our mountain, told me that he noticed an increase in purple finches at his feeders over the last five years and had had 12 in April. Charlie and Marge Hoyer, my closest neighbors on the mountain–three miles as the crow flies–had 6 to 8 house finches at their feeders last winter.
I hypothesize that, for the most part, these urban, suburban and farm-loving birds only stray to wilder places when their numbers are high. The nearest bird feeders to mine are probably two miles away in the valley. That’s not too far for house finches to range. Andrew Davis, who radio-tracked them in Ithaca, New York, from one backyard feeder to another, found that they could easily range from one to two miles a day.
Davis also studied the winter-roosting behavior of house finches and discovered that their roosts only contain house finches. They use the same conifers more than 30 feet tall as roosting trees night after night. House finches begin arriving in the roost area and gathering in nearby deciduous trees two hours before dusk. Their numbers increase until half an hour before dusk, and then each bird flies silently into the thickest and highest part of the conifer tree or trees, depending on the size of the flock, and don’t move or make a sound after settling down for the night.
It is their winter-flocking habit, as well as the long distance dispersal of juveniles that helped to quickly spread conjunctivitis. Also, because eastern house finches originated from a small number of released birds, they are highly inbred and have low genetic diversity, which may have made them more susceptible to the disease.
Scientists have been surprised at the longevity of the disease. Most diseases run their course in a few years once a large proportion of a population is eliminated as eastern house finches were. Instead, it has continued to spread across North America. In the winter of 2004, the North West house finch population experienced their first widespread epidemic of house finch eye disease. Here in the East, Cornell scientists estimate that five to ten percent of house finches now have conjunctivitis, but that it is no longer a dire threat to the species.
Researchers Andre A. Dhondt, who has been studying this surprising disease from the beginning, and Melanie Driscoll have learned that it rises at the end of summer and peaks in autumn. Then it declines to a mid-winter minimum, increases to an early spring peak, and returns to minimal numbers during the breeding season.
House finches still remain among the most common feeder species even though their flock size continues to fall, dropping to record or near-record lows in the East and North Pacific areas, as of the winter of 2004-2005, according to the reports from participants in Project FeederWatch.
I suppose that sooner or later a few house finches will find my feeders again. Next time I won’t take them for granted. If there is any lesson I’ve learned over my decades of nature-watching, it is that nothing remains the same.
Marcia Bonta 
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