House Finch

All the House Finches we see in New Hampshire are the descendants of a handful released on Long Island in the 1940s. Originally native to Mexico and the southwestern United States, they were brought east to be sold as pets until – so the story goes – they were freed by a pet store to avoid persecution under migratory bird protection laws. It took a while for the finches to get a toehold in the New York City area, but by the 1960s they had spread to southern New England and Chesapeake Bay. The first New Hampshire records came in 1967 with birds in Hillsborough and Concord, and since then the species has spread through most of southern New Hampshire, although primarily where there are people.

The rapid rise of House Finch populations in the East was curtailed by the emergence of a conjunctivitis strain that caused considerable mortality, and numbers dropped quicky to the much lower levels where they remain today. The birds’ high vulnerability to this disease was likely due to low genetic diversity since all House Finches east of the Great Plains are all descended from those original birds released on Long Island. Conjunctivitis is still present in New Hampshire finches, so if you see birds at feeders that are lethargic and have crusty or swollen eyes you should take in the feeders, clean them thoroughly, and wait two weeks before putting them back outside. This will minimize the risk of transmitting the disease to other birds.

For a non-native bird, the impact of House Finches on native species appears minimal. The exception might be the Purple Finch, which showed declines during the 1970s and 1980s as House Finches were increasing. After the latter’s precipitous decline in the 1990s, Purple Finch populations stabilized over much of the Northeast. The only study of interactions between the two species showed that House Finches were socially dominant over Purples at feeders, which certainly could have had negative effects on winter survival. And even though their population is no longer in steep decline, Purple Finches are still outnumbered by House Finches in southern New Hampshire, even during invasion years. Telling the two apart is a common problem for backyard birders. The best field marks to look for are the shade of red (Purples have more of a raspberry tinge than plain red), streaking on the underparts (male Purples have none), and facial pattern (female Purples have a distinct whitish triangle around their cheeks).