Male House Finch - Photo: Dow Lambert

The Surprising House Finch

by Bob Boekelheide

September 2024

The other day, Rebecca Atherton asked me a question that made me think twice. Her question: is the House Finch native to Washington state? It turns out that House Finches are considered native to WA, probably arriving on their own somewhere in WA without intentional human introductions. But their history is more complicated than what you might think, considering that they are now a common backyard bird throughout human habitats around the Salish Sea.

The House Finch is the poster-child for a species that has undergone rapid range expansion over the last 100 years, not only in WA, but throughout the United States and southern Canada. Up until the 20th century, House Finches were mostly known as a bird of the arid Southwest and California lowlands. As late as the 1930s, they were considered rare on the west side of the Cascades, even as far south as the Willamette Valley of Oregon.

According to Birds of Washington State, House Finches apparently colonized eastern Washington before they moved into western WA, with some appearing in eastern WA as early as 1885, then more expansion through the first half of the 20th century. During that time, they even moved north into the Okanagan Valley in British Columbia. The dry brushlands and towns of eastern WA must have felt like home to newly-settled House Finches.

*Female House Finch - Photo: Dow Lambert*

House Finches apparently arrived even later in western WA. Surprisingly, bird records show that House Finches were considered “casual” in western WA until the early 1950s, meaning they were not recorded every year. The first nesting records of House Finches in western WA occurred in the 1950s, although it’s not exactly clear where that occurred. They must have expanded rapidly after that, reaching the north Olympic Peninsula sometime between the 1950s and the 1970s. The very first Sequim-Dungeness Christmas Bird Count in 1975 tallied a nice total of 301 House Finches. For comparison, our most recent SDCBC in December, 2023, tallied 1448 House Finches, an all-time record.

Does this pattern remind you of other species? In a way, it seems similar to Anna’s Hummingbirds and California Scrub-Jays, species invading WA more recently from the south. It’s been suggested that these species’ movements are exacerbated by climate change, but can we blame climate change for House Finches moving north 50 to 100 years ago? All three species thrive in human habitats, so as towns and suburbs expand, and bird feeders proliferate, so do these birds. Similar to our hummingbird feeders that now support Anna’s Hummingbirds, so, too, our sunflower and millet seed feeders keep House Finches happy.

Another possibility is that House Finches didn’t move onto the Olympic Peninsula from the south at all, but actually from the north. Say what? It turns out a small population of House Finches established itself in Victoria BC as early as the 1930s. Where did they come from? Did someone purposefully release House Finches in Victoria, and they subsequently spread around the Salish Sea? Unfortunately, we’ll never know. It is known, however, that House Finches were kept as cage birds in the early 20th century, known as “Hollywood Finches.” It makes me wonder whether releases of captive Hollywood Finches could have created the satellite Victoria population. It hints that House Finches may not be native to all areas of western WA after all.

Regardless of where they came from, the eastern lowlands of Clallam County, particularly around Sequim, now have some of the highest annual abundances of House Finches anywhere in WA state, according to eBird Status and Trend maps (available at https://science.ebird.org/en/status-and-trends). Sequim provides just about everything that House Finches desire: relatively moderate year-round climate, not much winter snow-cover, a mix of human habitation and agricultural areas, and lots of bird feeders eagerly supplied by compliant humans.

The eastern half of North America is a different story. In 1939, a number of House Finches (aka Hollywood Finches) were trapped in Santa Barbara, CA, and delivered to a pet store on Long Island, NY. Apparently about that time the USFWS began cracking down on the domestic sale of wild birds. What did the pet store do, if it couldn’t sell the finches? Let them go, of course. For the next decade or so the House Finch population remained on Long Island, then House Finches rapidly expanded throughout the eastern US and southeastern Canada. They now are a fairly common backyard bird throughout the eastern US. The eastern population even mingles with the western population across the Great Plains, one of the most remarkable expansions of any species in North America.

Despite their overall abundance, House Finch numbers still vary quite a bit between years. A look at Sequim-Dungeness Christmas Bird Count (SDCBC) data for the last thirty years shows a fairly steady decline in House Finches from the 1990s to 2014, based on the number of finches we counted per party hour on the CBC (Figure 1). After 2014, their numbers zigzagged upwards again. Mind you, CBC data only occurs on one day out of the entire year, so it is an instantaneous, but somewhat incomplete, snapshot of birds in mid-December.

Year-round data from our Wednesday morning bird walks at Railroad Bridge Park may provide a better view of annual changes in House Finch numbers for the 20 years between 2002 and 2021 (Figure 2). It, too, shows significant dips and jumps in abundance between years. Although not all years correlate between the CBC and Wednesday bird walk data, there are some similarities. In general, the years between 2011 and 2014 show lower numbers, leading to more recent increases.

One reason for annual variability in House Finch numbers is epidemics that pass through their population from time to time. If you have bird feeders, you may have seen House Finches with horrible lesions on their faces, clustered around their eyes. This is conjunctivitis caused by an infection of Mycoplasma, a dangerous bacterium found in poultry and other birds. As the Mycoplasmal conjunctivitis passes through a population, House Finch numbers crash as birds die off, then they slowly recover as individuals with immunity survive to breed again. Even though other species may be infected, it really hits House Finches hard, sometimes wiping out over half the population. Hence it is sometimes called “House Finch Disease.”

*House Finch with conjunctivitis - Photo: Dow Lambert*

It turns out that House Finches have a very regular annual cycle at Railroad Bridge Park, as revealed by 20 years of Wednesday morning bird walk data (Figure 3). The graph shows that their lowest numbers occur in April at the start of the nesting season, when birds are on territories and cryptic females try not to be seen. Their highest numbers occur in September after chicks have fledged and large flocks travel around together. It may also be that RR Bridge Park attracts more House Finches outside the nesting season, when finches congregate in backyard and brushy habitats along the Olympic Discovery Trail from August to January. They particularly like the River Center’s feeders and berry bushes near Runnion Road.

The pattern is more extreme at Three Crabs beach. As part of the Three Crabs Restoration Project from 2014 to 2018, OPAS volunteers counted House Finches at Three Crabs beach three times each month. Large numbers of House Finches, sometimes several hundred at a time, flock at the shores of Dungeness Bay between June and November, peaking in August and September (Figure 4). The finches don’t stay at the beach during winter; once days grow shorter and temperatures drop, they leave the beach and move inland to town and backyard feeders.

Which leads to another question: Do local House Finches migrate? Some House Finch populations disperse south during winter, particularly in the northern part of their range, like in the Midwest. The best evidence is that House Finches in western WA do not migrate, but they definitely disperse to more favorable habitats and food sources following the nesting season. Dispersal is the key – they have the ability to hop, skip, and jump to new locations, which has enabled them to spread through human-occupied areas of North America.

Like other finches, House Finches are sexually dimorphic. Females are cryptically-colored brownish-gray so they remain camouflaged while incubating, whereas males have fire-engine-red heads, breasts, and rumps. The red coloration in males comes from carotenoid pigments in their diet, with the red increasing in intensity as they age. Studies have shown that female House Finches prefer males with large bright red patches.

Sometimes we see yellow or orange males that have not developed red pigmentation, perhaps because they are younger or perhaps because they do not have enough carotenoids in their diet. There is also evidence that ectoparasites such as mites and feather lice affect the plumages of males. One study showed that males with heavy parasite load were more likely to be shades of orange or yellow, whereas all the males with no parasites were red. Conclusion: you don’t want parasites.

What we know about the breeding biology of House Finches comes from a handful of studies from diverse places like Montana, Michigan, Alabama, and Arizona. Unfortunately, there are no similar studies from coastal WA. Just about everywhere, though, these studies reveal that House Finches typically pair up during winter and begin building nests as early as late February and March. Even though both sexes assist in choosing a nest site, only the female builds the nest and incubates the eggs. The male feeds the female both on and off the nest while she incubates.

There’s really nothing about the breeding biology of the House Finch that makes it a candidate for explosive population growth. House Finch clutch sizes average four or five eggs, ranging from two to seven eggs. Like most songbirds, nest losses due to predation can be high, sometimes more than half of their nests. Most studies show an average of about two chicks fledged per attempted nest, and about 3.5 chicks fledged per successful nest.

With an incubation period of about 14 days and chicks in the nest for another 15 to 18 days, House Finches can squeeze off several nest attempts between March and July. Most House Finch females attempt at least two broods in a successful season, but some may attempt as many as five or six clutches, even though nesting success declines steeply with later broods. The male continues to feed their chicks for several days after fledging, whereas the female promptly begins laying eggs for the next clutch.

*Fledgling House Finch - Photo: Dow Lambert*

Fledgling House Finches often look like they have “horns,” the remains of downy feathers from their chick period.

Unlike many songbirds, finches are renowned for feeding almost no insects to their chicks, instead feeding them lots of plant seeds and buds. One study in California showed that 98 percent of food items fed to House Finch chicks was plant material, but only 2 percent from animal sources probably ingested with the plants. Seed choice undoubtedly depends on when different crops mature, so seeds like dandelions might dominate early in the season and seeds like thistles might come later. Adults feed the chicks by passing congealed masses of seeds from their own crop right into the chicks’ mouths.

There are a few curious things about House Finch eggs, chicks, and gender. First, a study in Montana found that eggs containing female embryos averaged larger than eggs containing male embryos, so at hatching female chicks are larger than male chicks. In Arizona, where blood-sucking nest mites can compromise chick growth, the last egg laid in a clutch is almost always male, apparently because male chicks have faster growth rates and may leave the nest two to three days earlier than female chicks, hopefully to escape the worst of the mite infestation. Surprisingly, fast-growing male chicks from the last eggs in a clutch had the best survival rates if there was a mite infestation in the nest.

How old do House Finches get? Like many passerines, not very old. The oldest male in a population of banded birds in Montana was 12 years old, whereas the oldest female was 10 years old. These are clearly outliers compared to the rest of the population, which die at a much younger age. Annual adult survival varied from about 40 percent in Michigan to about 58 percent in Arizona, so about half the adults die off each year. This means that only about 10 percent make it to five years old, and far less than one percent make it to 10 years old.

After researching this article, I’m even more puzzled by House Finches. We take them so much for granted, yet they are relative newcomers to the avifauna of western WA. Their droll chirps and sing-songy melodies are now common backyard sounds, but it has not always been that way. Did they really get to north Olympic Peninsula on their own? I’m afraid we’ll never know for sure.

Many of the interesting facts about House Finches contained in this story came from Birds of the World, an on-line resource available through Cornell Lab of Ornithology. I highly recommend that all bird aficionados subscribe to Birds of the World, both for the information and to support the Lab of Ornithology.