House finches are small, sociable songbirds that are native to the western United States. However, they have become established in the eastern United States after being introduced from the west in the 1940s. As a result, house finches are now found across most of North America. Their rapid spread and ability to thrive in human-modified environments has led some people to consider them an invasive species. This article will examine the background of house finches in the US and evaluate whether they can be considered invasive.
What are house finches?
House finches (Haemorhous mexicanus) are small passerine birds in the finch family Fringillidae. They have a wingspan of about 20-25 cm and weigh 18-27g. Males have reddish-brown heads, breasts, and rumps, with brown streaking on their underparts and white bellies. Females and juveniles are brown-streaked overall with less reddish coloration. House finches are highly social and form large flocks outside of breeding season. They have delightful musical warbling calls.
House finches are originally native to the southwestern United States and Mexico. Their native range stretches from Oregon to southern Mexico. Within their native range, house finches occupy open and semi-open habitats including deserts, scrublands, farms, and suburbs. They are strongly associated with human habitation.
History of house finches in the eastern US
In the 1940s, a small number of house finches were introduced to Long Island, New York from their native western range. These birds had been captured for the pet trade. When they escaped or were released, they found the human-modified environments of the east highly suitable habitat.
The house finch population expanded rapidly across the eastern US and Canada in subsequent decades. Within just 20 years of their introduction, house finches were found from coast to coast. They had colonized most of the eastern United States by the 1980s. Today, house finches are abundant year-round residents across nearly the entire continental US and southern Canada. Densities are highest in the east. Their range also spills into Central America and Mexico.
Are house finches invasive in the US?
The house finch’s introduction to the east and subsequent spread has led many sources to label them an invasive species. But do they truly meet the criteria to be considered invasive?
Invasive species criteria
Invasive species are defined by ecologists as non-native organisms that cause economic or environmental harm in their introduced range. More specifically, to be considered invasive, scientists typically require organisms to meet these criteria:
- Introduced to regions beyond their native range through human actions
- Establish rapidly growing self-sustaining populations in new regions
- Spread over a large area from introduction sites
- Cause harm to the economy, environment, or human health in their non-native range
Let’s evaluate how well house finches match these major invasive species benchmarks.
Non-native introductions
House finches clearly meet the first criteria of being non-native species introduced to new regions by humans. Native house finches exist only in western North America and Mexico. But human transport of captured pet birds directly enabled house finches to become established across eastern North America starting in the 1940s.
Rapid spread and establishment
House finches also easily meet the second criterion of rapid population growth and establishment following introduction. After their initial escapes/releases on Long Island, house finch populations grew exponentially across eastern North America. They quickly colonized diverse habitats from suburban yards to city centers. Within just two decades, house finches occupied most of their current transcontinental range.
Year | House finch range expansion on the east coast |
---|---|
1940 | Introduced on Long Island, NY |
1960 | Present across New England and Mid-Atlantic states south to Virginia |
1980 | Occupied entire eastern US and southern Canada |
Their populations remain robust today, clearly demonstrating successful establishment and spread following introduction.
Harm to new environments?
The last criteria of causing environmental or economic harm in their non-native range is the biggest point of contention for categorizing house finches as fully invasive.
Research shows mixed results on whether introduced house finches negatively affect other species in eastern ecosystems. Some studies have found house finches dominate bird feeders and compete with native birds like purple finches. Other studies suggest they fill an open niche and do not harm native species. Evidence overall suggests house finches integrate into eastern bird communities without major disruptions.
There is also no evidence house finches harm ecosystems through overgrazing, predation, or other means in their expanded range. Most ecologists conclude house finches naturalize but do not become aggressively invasive in eastern North America. Their advantages appear confined to human-provided food and nest sites.
However, one area house finches may negatively impact is agriculture. One analysis estimated house finches cause $108 million in damage to California orchards each year through fruit contamination. But further study is needed to quantify their impacts to agriculture in other regions.
Conclusion
So are house finches invasive species? They unambiguously meet the first two criteria of being introduced non-native birds that establish rapidly expanding populations across eastern North America. However, their limited environmental impacts and mixed evidence for competitively harming native species currently precludes them from being considered fully invasive.
Summary
- House finches are native to the western US and Mexico but were introduced to the eastern US in the 1940s
- They spread quickly across the east, occupying most of their current range by the 1980s
- High populations but mixed evidence that they harm native ecosystems or species in their expanded range
- May cause agricultural damage but further study is needed
- Currently best classified as introduced species rather than a fully invasive pest
Rather than an irreversibly damaging invasive species, house finches appear to be successful human-adapted colonizers. Their attractive songs and readiness to visit bird feeders have made them welcome additions to many eastern backyards. While local impacts should continue to be monitored, house finches largely appear to have found a suitable and non-disruptive home across most of North America.