What's Different About These Common Birds? Part 1

Most birders realize that individual bird species can show significant geographic variation. In fact, the differences in size and plumage can be radical. Classic examples include the Aleutian Song Sparrow, which dwarfs its con-specifics, and the “Blue” Snow Goose, which is almost totally lacking in white plumage and bears little resemblance to a typical Snow Goose. A recent trip to Baja California Sur (B.C.S.), Mexico exposed me to rather odd-looking populations of three species that I see regularly near my home in the Pacific Northwest. I was amazed when I saw Acorn Woodpeckers, “San Lucas” American Robins, and male House Finches in the Cape District of B.C.S., as they were quite unlike the populations that reside in the U.S. Unfortunately, standard field guides do not offer illustrations of these interesting variants, so I thought a series of photo essays was in order. The first bird we’ll explore is the House Finch.

The Ultra-Red House Finches of Baja California Sur

Before our trip, my travel mate Steve Mlodinow, who was making his 15th trip to Baja, warned me that I would see several local populations in B.C.S. that would look dramatically different than those of the same species in the Pacific Northwest. One example he cited was the House Finch, explaining that I would not believe how brightly colored they are. He was right. Had I not known in advance that Purple Finches do not occur in B.C.S., I might have called the first male House Finch I saw a Purple. I’ve read (but can’t remember where) that the amount of red these finches show is simply a reflection of diet. Perhaps the B.C.S. birds are getting into cans of fire engine paint. They are really red!

This male House Finch was photographed in Eugene, Oregon 25 December 2008. In terms of red on the head and breast, it’s fairly typical of the local resident population. In the Pacific Northwest, the red on the crown is most intense and generally limited to the forehead, forecrown, and supercilium. In this regard, this individual is near maximum red. The mid-crown and hind-crown on these House Finches is normally medium gray-brown, which creates the red “eye-browed” look shown by this bird. Note also that there is a lot of gray and gray-brown in the auriculars, nape, and hind-neck of this bird, which contributes to the patterned face and head one typically associates with a male House Finch. The red on the underparts is most evident on the breast and tends to fade to paler pink and off-white below. As shown by this individual, northerly male House Finches generally show heavier and more extensive brown streaking along the flanks, belly, and to a lesser extent the lower breast than other members of the Carpodacus genus--Cassin’s and Purple Finches. (Photo by David Irons using a Canon EOS XSI 450D camera and a EF 100-400mm f/4.5-5.6 lens)

Many birders in the U.S. would take one look at this bird and call it a male Purple Finch. However, it was photographed 8 January 2009 at San Jose del Cabo, Baja California Sur, Mexico, where Purple Finches do not occur. It is a male House Finch exhibiting the typical appearance of the local population. The extensive red on the head and underparts was utterly unlike that of any House Finch one might encounter in the U.S. Nearly the entire head, including the nape and crown, was solid red with only a little brown showing in the auriculars. The throat, breast, most of the belly, and the flanks were also near-solid fire engine red with only a hint of the expected brown streaking. Though not apparent in this image, the back and wings of this bird also showed far more extensive red than we might expect on a House Finch in the U.S. This bird was comparatively un-streaked below. (Photo by David Irons using a Canon EOS XSI 450D camera and a EF 100-400mm f/4.5-5.6 lens).

In the next BirdFellow Journal post, I’ll compare typical American Robins to the unique “San Lucas” Robins found in the higher elevations of Baja California Sur.


Thanks, Dave, for posting these interesting photos of brightly-colored House Finches from BCS. I was there in Cabo San Lucas last March, just overnight, catching a boat in the early morning. I didn’t notice these birds—I’m sure I heard and identified House Finches in town but didn’t look closely enough!

I have another supporting identification mark to help separate these birds from similar Purple or Cassin’s Finches in other parts of North America. House Finches have smaller bills and a very curved culmen (the ridge on the upper bill from tip to forehead). Your photos show the short bills and curved culmen very well!

That said, Cassin’s has the longest bill and straightest culmen of the three species. Western forms of the Purple Finch also tend to have longer bills, with slightly curved culmens. The Eastern Purple Finch has a shorter bill with a bit more curve to the culmen, but still not “stubby” as described for House Finch.

The book Advanced Birding by Kenn Kaufman (1990) describes this and other identification tips—but doesn’t discuss the bright House Finches of Baja!



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