See my detailed discussion of White-crowned subspecies here, which needs updating with the information below.
In early May 2011 I spent several days in southeastern Arizona, and devoted a lot of time to studying the White-crowned Sparrows. At that date most of them were migrant Interior West birds of subspecies Z. l. oriantha. Most of the local wintering population of Western Taiga subspecies Z. l. gambelii had already migrated north, but a few were still present and offered excellent comparisons. On 1 May I watched and photographed a few dozen birds at the San Pedro House feeders, and discovered a number of differences (details and photos below).
The Interior West subspecies oriantha has sometimes been considered the same subspecies as the Eastern Taiga leucophrys, because they were thought to be indistinguishable by appearance, but lumping them makes no sense biogeographically. My study of these birds revealed (as I suspected) that the Interior West birds differ in a number of subtle but significant ways from the Western Taiga birds. In contrast, Eastern Taiga birds have always struck me as simply dark-lored ((It is worth noting that the term “lores” is used loosely here, the color difference in these sparrows is largely above the lores, on the supraloral, but it’s easier and at least partly correct to call it the lores.)) and pink-billed versions of Western Taiga. So presumably all of the differences noted here (aside from bill color and lore color) should work to distinguish Interior West from Eastern Taiga, but that remains to be tested.
Western Taiga (left) and Interior West (right) White-crowned Sparrows, 1 May 2011 at San Pedro House, Arizona. Frame captures from video copyright David Sibley.
Interior West oriantha vs Western Taiga gambelii
- lores blackish (vs pale gray)
Some variation in Interior West birds involves pale gray invading from below, and may represent intergradation.
- bill pinkish tinged orange, often with dusky wash and culmen (vs bill orange tinged pink, usually paler and cleaner)
This is surprisingly difficult to ascertain. Similar to the Greater White-fronted Goose subspecies problem, an orange-billed bird stands out among a group of pink bills, but then scanning and trying to quickly sort birds on bill color is impossible, and judging bill color on a lone bird is difficult.
- more obvious and broader white throat area extending onto malar on Interior West (vs. more restricted pale area forming a relatively narrow and inconspicuous pale patch when viewed from front)
This is fairly obvious when comparing the two subspecies side by side, but probably much more difficult to judge in isolation.
- cleaner gray nape with broad gray streaks merging into upper back on Interior West (vs brown streaks on nape and upper back forming sharp boundary between gray nape and brown-streaked back)
- larger white tips on wing coverts
- overall larger and bulkier
- richer reddish-brown edges on tertials (vs. paler reddish-brown)
- dark streaks on back richer reddish-brown (vs dark dusky brown and blackish)
- lateral crown stripes broader in front and narrower to rear (vs more uniform width throughout)
- crown averages brighter, almost all have very bright white crown including eyebrow that wraps around back of head (vs median crown stripe and eyebrow become gray before end of black stripes)
Photos don’t show this very well, but it was obvious in the field. Females have distinctly drabber crown patterns than males, and it’s possible that the few remaining Western Taiga birds in this location were all females. This deserves more study.
- crown often raised, bushy (vs usually held flat)
These are great comparison photos. Where I live in w. Oregon, the interior dark-lored
White-crowneds (subspecies oriantha) are quite rare, though they nest in some of the mountains of e. Oregon. Shawneen Finnegan and I spent time studying them along the summit of Winter Ridge in Lake Co., Oregon last June (2010). Of course at that time of year there were no gambelii present for comparison. However, we get lots of opportunity to compare the “Western Taiga” White-crowneds (subspecies gambelii) with the “Coastal” form (subspecies pugetensis) that is resident in w. Oregon. In addition to the differences in color on the upperparts (more chestnut and gray on gambelii) and the brighter gray underparts of gambelii, the first thing I usually notice about the Western Taiga birds is that their crown is what I refer to as white dominant, whereas the pugetensis (and apparently oriantha based on your images) have a crown/head pattern that is more black dominant. As you point out, the lateral crown stripes of oriantha (same is true for pugetensis) are much broader on the forecrown, which effectively diminishes that amount of white that catches your eye. In flocks containing breeding plumaged adults of both pugetensis and gambelii (usually mid-March to late April in w. Oregon), this is often the best visual clue for separating these two subspecies. Based on your photo essay, this seems to be the case with oriantha and gambelii as well.
A valuable set of data David – thank you. Two things:
1) I think that technically the lores are mostly gray on both forms; on oriantha there is a thin black line that angles up from the front of the eye to meet the lower front corner of the black lateral crown stripe, leaving the main part of the lores (from the bill back to just ahead of the eye) gray. When In Fort Worth I saw small numbers of oriantha and a much smaller number of gambelli mixed in with the eastern form, and I needed the right angle to be sure I could eliminate that thin angled dark “supraloral”? to be sure of a gambelli, as on some birds (intergrades??) there seemed to be a “shadow” or remnant version of this thin black angled line.
2) Looking at your very instructive pics, one thing that strikes me is that on gambelli the black lateral crown stripes are parallel from the centre of the crown to their rearmost extent, while on oriantha they taper back closer to each other, making the width of the white gap narrower – actually this same trait is repeated on the lower black crown lines, such that the gray gap is also narrower on oriantha than on gambelli.
I dont know if this holds up on a larger sample size, but in your photos it seems quite striking.
Regards,
Martin
Thanks for the comments. It’s interesting to me that both you and Dave commented on the “black-dominant” crown of oriantha in these photos. My impression while watching them (and written in my notes) was that the white was brighter and more obvious on oriantha than on gambelii. As I wrote above, on oriantha “crown averages brighter, almost all have very bright white crown including eyebrow that wraps around back of head (vs median crown stripe and eyebrow become gray before end of black stripes on gambelii). I think the video fails to record the subtle variations in pale gray, and makes both subspecies and males and females all appear bright white on the crown stripes.
There is certainly a difference in the extent of black, and I did notice this in the field saying that the black crown stripes of oriantha seem to taper and end more quickly than on gambelii, but in the field I think the broader black stripes on the forehead of oriantha are counteracted to some extent by its brighter white stripes, so an observer is more likely to comment on the bright “whiteness” of oriantha rather than the extent of black.