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It's not often that I look at close-up, in-focus images of a North American bird and can't identify it. And yet, there are some species (think gulls) and species pairs whose basic and immature plumages continue to challenge even the most experienced birders. Plectrophenax (Snow and McKay's) buntings fall into this category.
One such bird is currently challenging local birders here in Portland, Oregon. On 25 November 2011, Tom McNamara found a "Snow Bunting" on Broughton Beach along the south shore of the Columbia River just north of Portland International Airport (PDX). Over the ensuing several weeks it was seen somewhat sporadically along this stretch of beach.
A few days ago, the bird was observed at an alternate location adjacent to the PDX Fire Station, which is situated along the north boundary of the airport property. The bunting has proven to be far more reliable at the latter site, allowing many folks to drive right up to it, resulting in some stunning photos. The average birder in Western Oregon (west of the Cascades) does not see Snow Bunting annually although they do occur in small numbers along the northern coast (Marshall et al, 2006). We are also in range of the occasional stray McKay's Bunting, including a bird found the exact same day in coastal southern Oregon, that Jon Dunn and Dan Gibson said looked like a good McKay's (pers comm.). Dave Irons wrote a BirdFellow piece earlier about this bird that can be found here. The previous Oregon records of McKay's Bunting are 2 birds in a flock of Snow Buntings at the south jetty of the Columbia River from 23 February to 9 March 1980 (Marshall et al, 2006) and one male on 3 January 2004 at Depoe Bay (OBRC, 2010).
After failing to locate the bird during a couple of prior searches at Broughton Beach, Dave Irons and I finally saw the bunting at the PDX Fire Station on 18 December. Dave got some nice pictures of it. Upon downloading and reviewing these images, we were struggling to age and sex the bird. Some aspects of the bird were puzzling to both of us, most notably the unstreaked white rump and lower back (only minimal rusty wash) and the pattern of white in the folded wing, which seemed to show too much white for a female Snow Bunting and not enough for a male. These ambiguities caused us to consider that this bird might be a female McKay's Bunting, or, perhaps, a Snow Bunting X McKay's Bunting. Despite an extensive review of our published literature and online resources, we remained perplexed. Snow and McKay's Buntings are closely related and are presumed to occasionally hybridize where their ranges overlap (Birds of North America Online). In their basic (winter) plumages, adult female McKay's Buntings are quite similar to male Snow Buntings.
According to the McKay's and Snow Bunting accounts in the "Identification Guide to North American Birds: Part I Columbidae to Ploceidae" (Pyle 1997), some features of this bunting more closely match Snow Bunting, particularly the wing pattern. And what sex it is? According to Rogers (2005) the shape of dark centers to the central scapulars will help determine whether it is male or female. Females of both species show relatively small black centers and always taper to a point. The shape and size of the black in male Snow Bunting is larger, broader and may not end in a point. The size and shape of the Portland bunting's central scapulars look broad and pointed, appearing to be more like a male to my eye.
One might also conclude that it is a male since the wings look rather black in most of the photos and there is a crisper lateral transition to white near the base of the primaries, whereas females should be grayer and the gray extends up farther onto the inner web. But are the feathers really black or is it an exposure issue? And in the outstretched wing shot below (Fig. 3) there is a tongue of black extending up the inner web. The longest primary covert and greater alula on a McKay's is typically mostly white with the exception of a hatch year or second year female. We were left with more questions after reviewing "Identifying McKay's Bunting" (Rogers 2005). It includes a photo of a bird photographed at Richmond, British Columbia on 20 December 2004, which is identified as a female McKay's (Fig. 6 pg 624). In terms of overall pattern, back color, and the pattern and color of the folded wings, it looks much like the Portland bird with some exceptions. Note that both the Portland bird and the British Columbia bird (Rogers 2005) were photographed during the third week of December.
Other features mentioned as good for McKay's include an unstreaked white rump, yet I was able to find photos of winter Snow Buntings on the web that had white rump, including this one found in California in 2004. Generally, the rumps of a Snow Bunting are darker than those of McKay's.
The pattern of R3 (or Rectrix #3) is apparently very important in distinguishing these two species (Fig. 4). According to Pyle (1997), R3 on McKay's is mostly white with a bit of black in the tip that is shaped like a boomerang, while in Snow Bunting R3 is largely black. It can clearly be seen below that the pattern of R3 is as described for McKay's Bunting. Yet R1 and R2 on basic male McKay's shouldn't be as black as this bird's tail according to Rogers' article.
While the pattern of R3 looks right for McKay's Bunting the amount of black in the wing and the extent of black in the scapulars looks more like a Snow Bunting. So, what is this bird's parentage? Comments are more than welcome as the intention of writing this piece is to stimulate discussion.
I must thank Don Nelson, Lyn Topinka, Tait Anderson, Tom McNamara and Dave Irons for generously sharing their photos. This discussion would not have been possible without access to these images.
Patterson, M. and R. W. Scheuering. 2006. Snow Bunting. Pg. 569-570 in Birds of Oregon: A General Reference. D. B. Marshall, M. G. Hunter, and A. L. Contreras, Eds. Oregon State University Press, Corvallis, Oregon.
Montgomerie, Robert and Bruce Lyon. 2011. McKay's Bunting (Plectrophenax hyperboreus), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/199
Montgomerie, Robert and Bruce Lyon. 2011. Snow Bunting (Plectrophenax nivalis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/198
Oregon Bird Records Commitee. 2010. OBRC Records Through 2010. PDF accessed online from http://www.oregonbirds.org/#.
Pyle, P. 1997. Identification Guide to North American Birds, Part 1: Columbidae to Ploceidae. Slate Creek Press, Bolinas, California.
Rogers, J. 2005. Identifying McKay's Bunting. Birding 37(6): 618-626.
Sibley, D. A. 2000. The Sibley Guide to Birds. Alfred A. Knopf, New York.