Birds
House Finch
Haemorhous mexicanus · also called house finches
Perched at a backyard feeder, a male house finch displays red plumage built entirely from pigments in his own diet, a visible record of foraging success that potential mates can judge at a glance across gardens throughout much of North America.
Overview
The house finch, Haemorhous mexicanus, is a widespread songbird native to desert and grassland habitat across much of North America. Its diet-dependent red male colouring, accidental establishment across the eastern United States through the illegal cage-bird trade, and vulnerability to a significant conjunctivitis epidemic make it one of the more ecologically and historically interesting songbirds found anywhere on the continent.
A colour built from breakfast
Unlike birds whose colours are fixed by genetics alone, the house finch’s male red plumage is a direct reflection of diet quality, turning something as simple as feeder seed into a visible signal that shapes which males succeed in attracting a mate.
Status
Least Concern, remaining widespread and abundant across suitable desert and grassland habitat throughout both its original western range and the introduced eastern population.
House Finch: common questions
Why do male house finches vary so much in how red they look?
A male of this species develops red plumage from carotenoid pigments obtained through diet, meaning the intensity of red colouring can vary noticeably depending on the quality of food available, with females tending to favour more intensely red males as potential mates.
How did the house finch spread to the eastern United States?
This species was illegally sold as a cage bird in the eastern United States during the 1940s under a different name, and released or escaped individuals established a wild population that later spread widely, eventually meeting up with the species' original western range.
What disease has affected house finch populations?
This species experienced a significant disease outbreak beginning in the 1990s involving a bacterial conjunctivitis that spread rapidly through populations, causing eye swelling severe enough to impair the birds' ability to forage and avoid predators effectively.
Where is the house finch originally from?
This species was originally native only to western North America, favouring desert and grassland habitat, before an accidental introduction linked to the illegal cage-bird trade established a separate population across the eastern half of the continent.