The purple finch is a small songbird native to North America. As its name suggests, the male of the species has bright purple plumage. But why is this bird named for its vibrant coloration? In this article, we will explore the reasons behind the purple finch’s common name.
First, let’s start with a quick overview of the purple finch itself. This finch measures 4.7-6.3 inches in length and weighs 0.6-1.1 ounces. Its scientific name is Haemorhous purpureus. The purple finch breeds in Canada and the northeastern United States and migrates south for the winter.
The male purple finch has raspberry-red plumage on its head, breast, back and rump. Its belly and flanks are white. Females and juveniles have brown streaked plumage. The purple finch’s closest relative is the house finch.
Why Is It Purple?
So what makes the male purple finch appear purple? The answer has to do with the structure of its feathers. The feathers contain a pigment called carotenoid. As light hits these pigmented feathers, some wavelengths are absorbed while others are reflected. The reflected light appears to our eyes as purple.
Structural colors like this are common in the bird world. Hummingbirds get their iridescent throats from specialized feather structures. Blue jays also use nanostructures in their feathers to produce blue coloration. For the purple finch, the concentration of red carotenoid pigments combined with the structure of its feathers results in the stunning purple hue.
When Does It Turn Purple?
Male purple finches don’t hatch with purple plumage. Juveniles of both sexes have brown and white streaked feathers. Adult females retain this streaked brown appearance year-round.
Around their first fall, males will begin to acquire purple feathers through a complete molt. The process takes around 6 weeks as old feathers are replaced by freshly colored ones. By early winter, the male will appear fully purple. Its plumage remains this color until late summer when it sheds its feathers again before the fall.
So while “purple finch” seems like a misnomer for half of the year, it appropriately describes the male’s appearance during the colder months when most people observe them. The vivid plumage also occurs during mating season, catching the eyes of female finches.
Why So Purple?
The purple finch’s brilliant plumage didn’t come about by chance. Here are some of the leading theories as to why male purple finches evolved such a vibrant purple coloration:
Attracting Mates
In many bird species, females select mates based in part on the brightness of their plumage. Vivid colors signal that a male is healthy and reproductively fit. The purple finch’s coloring likely plays a role in attracting females during mating season. The striking hue stands out against winter backdrops of snow or bare trees.
Signaling Dominance
Brighter purple plumage may also signal a male’s social dominance. Older male finches tend to have deeper or more extensive purple coloring. Females may preferentially choose these males because their age and experience help them secure the best territories and food. The coordination required to produce complex plumage patterns also demonstrates neurological fitness.
Species Recognition
The purple hue helps purple finches recognize their own species and choose the correct mates. This prevents wasting energy on fruitless courtship or hybridization with other finch species. The house finch is nearly identical to the purple finch apart from its red rather than purple plumage.
Plumage Differences Between Males and Females
As mentioned above, male and female purple finches display markedly different plumage. But why did this difference evolve? Here are some explanations:
Camouflage
Female purple finches likely retained their brown streaked plumage as camouflage. While males only nest during the breeding season, females incubate eggs and care for the young. Cryptic feathers help conceal her vulnerable nest from predators.
Energy Conservation
Producing purple pigments may be energetically costly. By conserving this energy, females can devote more resources to laying and incubating eggs. The plainer plumage only needs to blend in with the background.
Gender Signaling
The contrast between male and female feather patterns makes each bird’s sex clearly identifiable. This allows males and females to easily find and court one another during the mating season. The differences also facilitate useful social interactions like territorial displays between rival males.
Geographic Variation in Purple Finches
While most purple finches display ruby red heads and rumps, not all populations have identical coloration. Here are some regional variations:
| Subspecies | Range | Plumage Notes |
|---|---|---|
| Haemorhous purpureus purpureus | Eastern North America | Bright, extensive purple on head, breast and back |
| Haemorhous purpureus californicus | Pacific Northwest | Dark or dull purple coloring |
| Haemorhous purpureus nevadensis | Southwestern North America | Small purplish area on head and rump |
These subtle differences in hue and extent of purple coloration stem from minor evolutionary divergences as populations became isolated. However, all purple finch subspecies retain enough key similarities to be considered a single species.
Conclusion
In summary, the purple finch earns its common name from the vibrant plumage of adult males. Structural colors produce this purple hue that probably evolved to attract mates, signal dominance, and facilitate species recognition. Females retain camouflage brown feathering better suited to nesting and parental duties. Some geographic variation in shading exists between subspecies, but the colorful male patterns remain. The next time you spot this striking bird, you’ll know exactly why it’s called a purple finch!
