A Bigger Range for the Lesser Goldfinch

From the Summer 2025 issue of Living Bird magazine. Subscribe now.

Lesser Goldfinch, the diminutive cousin of the familiar American Goldfinch, is found throughout the American Southwest from Texas to California (and south to South America), with populations breeding as far north as western Oregon and Washington. New research shows that in just a couple of decades, big numbers of Lesser Goldfinches have moved into eastern Washington and Oregon, as well as western Idaho—places that would rarely, if ever, have had the species just a few decades ago.

Researchers from Washington State University and the Cornell Lab of Ornithology analyzed bird-observation data from two participatory-science initiatives from the Cornell Lab—Project FeederWatch and eBird—to track Lesser Goldfinch range changes over the past 25 years. The study, published in the journal Ornithology in April, shows that Lesser Goldfinch year-round populations more than doubled in size in Washington State, while also increasing substantially in Idaho and Oregon.

“When I first arrived in eastern Washington [in 2019] I was pretty new to birding and Lesser Goldfinches were new to me,” said Mason Maron, lead author of the new study, who started this work as an independent researcher after graduating from Washington State University in 2023. “I was seeing groups of 30 or 40 at a time and I sort of assumed that was normal.”

But as Maron got to know the birding community, he soon learned otherwise. Kas Dumroese compiles the Christmas Bird Count data for two counties on opposites sides of a state border: Latah, Idaho, and Whitman, Washington. He tipped Maron off that Lesser Goldfinches were relatively new arrivals to the area.

“I found my first Lesser Goldfinch in Latah on July 5th, 2003. That was the second eBird record for the county,” says Dumroese, who has been birding in the area for more than 40 years. “It took about a decade to move from real rarity to more regular and expected. The species has been regular [on the Christmas Bird Count] since 2012, numbering from a couple of dozen to a high count of 413.”

In addition to quantifying how abundant Lesser Goldfinches were becoming in these new areas, Maron and his team tested some possible enabling factors for the range expansion. They identified warmer temperatures, more rainfall, urban development, and proximity to major rivers, such as the Snake and Clearwater Rivers, as key factors associated with the birds’ northward expansion.

“These rivers carry weedy plants and seeds really well,” says Maron, hypothesizing that disturbed areas along rivers would enable plants that Lesser Goldfinches use for food and nesting material, such as star thistle, to establish in new places.

Even though Lesser Goldfinches are a common feeder bird in their expanded range, Maron says feeders played a minimal role in establishing new populations.

“There wasn’t really a significant association with bird feeders,” he says. “The first individuals to arrive in a new area might go to feeders because they provide easy-to-access food, but … it’s not going to be enough to sustain a whole population.”

eBird Trends models show declining Lesser Goldfinch populations in some southern parts of their U.S. range, such as Arizona and New Mexico. That evidence may indicate a range shift of the species, rather than simply a range expansion to the north.

Jordan Boersma—a coauthor on the study, who earned his PhD from Washington State and now works as a research associate at the Cornell Lab—says the Lesser Goldfinch may be displaying remarkable adaptability that could show how some birds might thrive in a rapidly changing world: “Understanding how birds like the Lesser Goldfinch respond to climate change and urbanization helps us predict how other species might also be impacted.”