Three of the four North American subspecies of Orange-crowned Warbler occur in the Pacific Northwest. Each has a different status and migration pattern. Alert field observers can often differentiate between coastal birds and interior birds, contributing to our knowledge of their distribution and alerting us to changes in their status. In eBird, the three subspecies are
The last two are also clumped into “Gray-headed.” As this note points out, there are many times when birders are unable to confidently assign an individual to a subspecies. If in doubt, call it an Orange-crowned Warbler and avoid creating error in the data.
Distribution and Migration
When attempting to sort Orange-crowned Warblers to subspecies in the Pacific Northwest, general distribution is not always the best determining factor. Location and season are often better starting points.
Lutescens is predominantly found in the westside lowlands and the Cascades. They are short-distance migrants, mostly moving north-south along the Pacific coast. This subspecies winters in extremely low densities along the outer coast and in the lowlands west of the Cascades. The spring arrival of lutescens is earlier than the other subspecies, with the first migrants reaching western Oregon by late March (Fairchild and Alexander 2008).
Orestera is an interior breeder, the only subspecies breeding in interior mountain ranges such as the Selkirks, Blues, Wallowas, and Warners. Their status is uncertain in the Okanogan Highlands where both lutescens and orestera may occur (watch for intergrades). Orestera are also short distance migrants, mostly moving north-south in the interior, and spring migrants usually do not arrive until the last half of April, and passage extends into early May. Their winter status in the region is uncertain.
Celata is a northern taiga or boreal forest breeder, across a large area of northern Canada and most of the Alaska interior. Like other taiga breeders whose nesting ranges extend all across boreal Canada and into Alaska (i.e., Blackpoll Warbler, Alder Flycatcher), the migration route of this subspecies lies mostly east of the Rockies then fans out to the west once it has reached the boreal forest. Small numbers of celata are found west of the Rockies during migration, mirroring a pattern shown by several other taiga breeders like ‘Yellow-shafted’ Northern Flicker and ‘Red’ Fox Sparrow. Although the wintering status of celata in the region is poorly understood; it seems likely that many of the “Gray-headed” types found in winter in the Pacific Northwest are of this subspecies.
Identification in the field is full of pitfalls. The differences between the subspecies are subtle, and not much is known about how much interbreeding occurs where subspecies come into contact. We know that the breeding ranges of lutescens and celata meet in Alaska and presume that orestera and celata overlap to some extent in the Canadian Rockies. It is unknown if there is an overlap of orestera and lutescens on the breeding grounds. Observers must also contend with the effects of plumage wear, particularly in July/August. Size difference is frequently cited as a factor to sort to subspecies, although size differences are typically not discernible in the field. Observers should use several field marks, not just a single one, and recognize that many individuals are unidentifiable to subspecies. Good references include Dunn and Garrett (1997), Patterson (2011) and Pyle (1997). Birdfellow provides an excellent series of photos of Orange-crowned Warblers of each of these subspecies.
Well-marked individuals of each subspecies are identifiable with a combination of field marks, although differences between celata and orestera are often so miniscule that observers are encouraged to call most of them “Gray-headed” instead of trying to separate them.
eBird Northwest Data Entry
First a caution. When in doubt, just identify to species – this is still great information. Please do not enter subspecies unless you are really sure. For any subspecies outside of its normal range described below, include good notes with your report with distinguishing field marks and cues. Use the eBird media upload tool for photos and recordings to help justify and document your determination, when appropriate. While subspecies identification is really helpful for the finer points of conservation, incorrect guesses may undermine our understanding of how these birds are doing in breeding habitats, move seasonally, and respond to other factors like climate change. Be especially wary of identifying worn late summer to early fall birds.
Westside lowlands and the Cascades — Most OCWA in this region at any time of the year are lutescens, with the exception of fall montane migrant flocks at high elevations, near or above treeline. If you detect a gray-headed type in this area, it should be entered as “Gray-headed” unless there is clear evidence of breeding (e.g. nesting activity, sitting on a nest, feeding young), in which case they should be entered as orestera and documented in eBird with photos or good written description and using Breeding Codes. Celata may be more likely than orestera in winter, but birders should probably use “Gray-headed” rather than celata unless the identification is certain: for instance a very dull gray bird with the only yellow on the undertail coverts.
Okanogan Highlands — Breeding birds appear to be a poorly documented mix of lutescens and orestera, so any individuals not seen well should be entered without subspecies label. Intergrades probably occur, but are very difficult to recognize in the field; if you suspect an intergrade, it should be well-documented in ebird with photos and a good written description. Migrants could be any of the three subspecies.
Interior mountain ranges [Kalispells, Blue, Wallowa, Ochoco, Steens, Warner] — orestera is the default breeding species, any summer records of lutescens should be carefully documented. Migrants could include any subspecies, but lutescens should be recorded with care and some details noted. Migrants should be noted as Gray-headed, unless they are well marked orestera (for instance, fall birds in fresh plumage three-color appearance) or celata (grayish fall birds with only yellow on the undertail coverts).
Interior lowlands — Any of the three can occur as migrants and wintering birds, so eBirders should attempt to sort them into lutescens or Gray-headed when possible. Again, worn birds in late summer and early fall are problematic, so species-level identification is best for worn birds.
Dunn, J. and K. Garrett. 1997. A field guide to warblers of North America. Houghton Mifflin Co.
Fairchild, K. and J. Alexander. 2008. Using eBird to track latitudinal migration in Orange-crowned Warblers. Oregon Birds 34(4): 124-126.
Irons, D. 2002. CBC reports of Orange-crowned Warblers: a 20-year analysis and comparison with historical records. Oregon Birds 28(1): 9-10.
Patterson, M.J. 2011. OCWA, more than you wanted to know …. North Coast Diaries. http://www.surfbirds.com/community-blogs/northcoastdiaries/?p=183 (posted May 31, 2011; accessed December 2015).
Pyle, P. 1997. Identification guide to North American birds. Part 1. Slate Creek Press. Bolinas, CA.
Article by Bill Tweit and Dave Irons