All About Green Morph Pine Siskins

By Ryan F. Mandelbaum and Matthew Young:

Pine Siskins are hard to come by in much of the country during most winters, but this past fall’s irruption has made them regulars at many local birding spots, where they sometimes outnumber goldfinches and even house sparrows. If you’re lucky to be in a spot where Pine Siskins have become common, remember two things: first, that you should savor these birds while they stick around, and second, that there’s still the chance of finding a rare green morph.

Typical Pine Siskins might blend in with the local finches to the uninitiated. These small birds are the same size and shape as an American Goldfinch, but with dark brown streaking (like a House Finch), a markedly thinner bill, and yellow accents to the wing bars. But multiple studies of both museum skins and banded birds have found that around one percent of birds, all male, come in the mysterious “green morph.”

Green morph Pine Siskins look sort of like a typical Pine Siskin that has been jazzed up—check out Lillian and Don Stokes’ pictures here. These birds have darker greenish backs, yellowish fronts, bright yellow patches replacing the typical white wing bars, and yellow undertail coverts. Perhaps most importantly, they typically have reduced streaking on the front; in some cases, they may have “almost no heavy streaking below,” Robert Yunick wrote in his article. Green morph Pine Siskins have the same geographical distributions as the common Siskins.

The two traits most variable with green morphs seem to be how much does the individual have an overall wash of yellow (seems to range from almost the whole bird to just the key areas of extensive yellow in wing and undertail coverts) and how reduced the streaking is on the breast (ranges from modest amount of reduced diffuse streaking to very little streaking at all). In summary, average adult male Pine Siskin can have lots of yellow, but actual green morphs are typically a bit larger than average, and have greenish base color to the mantle with widely spaced streaking, extensive yellow in wings, plain faces, and yellow washed undertail coverts. Green morphs only exist in males, and only approximately 35% of Pine Siskins can be accurately sexed.

Green morph Pine Siskins might trip up birders familiar with Europe’s siskin species, the Eurasian Siskin, which has appeared in the United States as both a vagrant and as a released caged bird. However, female Eurasian Siskins have white undertail coverts and wing bars, unlike the green morph Pine Siskins’ yellow wing patches and yellow undertail coverts.

Whether green morph Pine Siskins represent a true “morph,” aberrant plumage, or simply the result of variations between individual birds is a question open to further study. All of this is pending further study—which you can help by recording your own observations of Pine Siskins in eBird and photographing potential “green morph” birds you encounter.

Hopefully, you’ve also experienced this year’s extreme Pine Siskin irruption to some capacity in your own parks or at your feeders. And, if you’re starting to feel a little Siskin fatigue, you might try finding a green morph of your own. 

Cover Photo Ronan O’Carra. Here’s the cover photo posted again just below.

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Here’s Alex Lamoreaux’s wonderful series of three photos showing the traits also mentioned above in body of article:

To reiterate, average adult male Pine Siskin can have lots of yellow, but actual green morphs are typically a bit larger than average, and have greenish base color to the mantle with widely spaced streaking, extensive yellow in wings, plain faces, and yellow washed undertail coverts. Green morphs only exist in males, and only approximately 35% of Pine Siskins can be accurately sexed. The two traits most variable with green morphs seem to be how much does the individual have an overall wash of yellow (seems to range from almost the whole bird to just the key areas of extensive yellow in wing and undertail coverts) and how reduced the streaking is on the breast (ranges from modest amount of reduced diffuse streaking to very little streaking at all).

For more on green morph Pine Siskins see the below links:

Nancy Castillo’s blog The Zen Birdfeeder

Max Brodie: https://ebird.org/checklist/S43370052

Sandy Aubol via Alex Sundvall: https://ebird.org/checklist/S74865712

Carter Dorscht: https://macaulaylibrary.org/asset/206271701

Ian Cruickshank: https://ebird.org/canada/checklist/S11221925

Macaulay Library “Green Morph” Pine Siskin photos