Purple Finch

Our state bird breeds throughout New Hampshire but is far more common in the north and west in coniferous and mixed forests. It is one of our “irruptive” species, meaning that the numbers we see in the winter fluctuate widely depending on food supply to the north. During the winter, they feed on a variety of seeds including conifers and mountain ash (plus sunflower at feeders). If there is a good seed crop in their core range in Canada, fewer will migrate south in the fall, and we see lower numbers at feeders. But when food is scarce to the north higher numbers migrate south and the species is more common in winter. Here in New Hampshire, peak fall migration generally occurs in October and November, and birds move back north in April.​

Purple Finches showed a consistent decline from the 1960s to early 1990s, after which the population appears to have leveled off. Reasons for the decline are highly speculative since the species is not well-studied despite being common and widespread. As a northern species, it could be responding to climate change – or to related changes in habitat or food supply – but we simply lack the data needed to evaluate this hypothesis. ​

Another option, proposed in the 1980s, is that Purple Finches were negatively influenced by competition with the closely related House Finch. The latter is not actually native to eastern North America, but was accidentally introduced to New York ​City in 1939 and gradually spread north, west, and south. Even though House Finches didn’t arrive in New Hampshire ​until the 1970s, their period of increase in the Northeast overlaps with the Purple Finch decline. The interaction ​between the two species has only been studied once, but this study found that House Finches were dominant over ​their native cousins 90% of the time. Could reduced access to food during winter carry over to lower reproductive ​success as has been shown for other birds? More study is clearly needed. There’s a more recent twist to this story. ​House Finches declined sharply in the mid-1990s as a result of a major conjunctivitis outbreak, and have since ​stabilized at much lower levels. Purple Finches stabilized around the same time, lending further credence ​to the competition hypothesis.