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Simply stated, sorting out many of the female and immature hummingbirds in the American West is a challenge. In addition to being very plastic in terms of shape and profile, feather iridescence and plumage variation associated with age combine to confound even the most experienced observers, particularly when it comes to the genus Selasphorus. This genus includes three North American species: Allen's Hummingbird, Broad-tailed Hummingbird, and Rufous Hummingbird. Separating them in their female and immature plumages has spawned many a lively debate.
On 11 June 2012 Shawneen Finnegan and I were birding along Cow Creek Rd. e. of Azalea, Douglas County, Oregon. We came across a yard full of blooming Red Hot Pokers (Kniphofia uvaria) that was teeming with Rufous Hummingbirds. It was hard to to count, but there were about 20-25 hummers buzzing about feeding on these flower heads. Almost all were immature or female-type Rufous Hummingbirds, so I found a roadside vantage point that allowed me to photograph several different individuals. Ultimately, I got photos of about ten different birds, all of which seemed to sub-adults. This photo essay shows some of the variation that one might see in immature Rufous Hummingbirds. I captured all of these images at the described site on 11 June 2012.
The first five photos show variation in back color, most notably how much rufous or rust color there is on the back, rump, and upper tail.
The next seven photos show variations in the throat pattern and flank coloration of immature Rufous Hummingbirds. Of particular interest to me is the amount of dark feathering each bird shows on the chin and center of the throat. Birds that were presumed to be immature males seemed to show more extensive and richer rufous wash on the flanks, along with more dense dark feathering on the throat.
I recognize that most folks reading this article aren't likely to invest much time and energy into aging and sexing every Rufous Hummingbird that they see (it can be an exercise in futility). Since I live in Oregon, where Rufous is the default Selasphorus across most of the state, appreciating the variability in Rufous Hummingbirds can come in handy. Occasionally, we see out-of-range reports of Allen's (nesting range extends to Oregon's southern coast) and Broad-tailed Hummingbirds (not known to nest in Oregon, but occurs as a rare migrant). Often times, such reports involve female/immature type birds. Here, the first order of business when considering a report of an out-of-range Selasphorus is to determine why it's not a Rufous.
In conclusion, it's important to point out that I've not studied museum skins of Rufous Hummingbirds, nor have I done any hummingbird banding, thus much of the commentary herein is speculative. I would welcome any comments on the specific age and sex of the birds in this collection of images. The main point was to display some of the individual variation one might encounter when observing this species in the field.
Howell, Steve N. G 2002. Hummingbirds of North America: The Photographic Guide. Academic Press: A Harcourt Science and Technology Company, London, UK.
Williamson, Sheri L. 2001. A Field Guide to the Hummingbirds of North America (Peterson Field Guide Series). Houghton Mifflin Co. New York, NY.
The links below provide additional photos of Rufous Hummingbirds and discussion of Selasphorus hummingbird ID.
Some might scoff at the notion that separating the western subspecies of Willow Flycatcher from Western Wood-Pewee can be challenging, but each year I see links to photos of one of these species that is misidentified as the other. The North American wood-pewees and Willow Flycatcher are similar in size, general shape, and coloration. Additionally, neither species typically shows an eyering and their wingbars are buffier and less crisp than those of other Empidonax flycatchers.
As a rule, most birders think of Empidonax flycatchers as being greenish above, pale olive-gray or yellowish below, as having complete eyerings and showing rather crisp and conspicuous wingbars.
We think of wood-pewees as being more dusky-brown above, with dingy grayish to dusky-olive underparts and dull sulphur-yellow that is limited to a narrow trough on the lower belly and undertail. Wood-pewees, particularly Westerns, look somewhat vested below with dark dusky-olive flanks and a paler central belly. The dark sides to the upper breast frame and accentuate a paler throat.
The general appearance of the "Western" Willow Flycatcher falls somewhere in between these two descriptions. In western North America Willow Flycatchers are browner above than other Empids and they generally show no eyering. While the smaller and grayer Hammond's and Dusky Flycatchers can look vested, most other Empids are not distinctly darker on the sides of the upper breast and upper flanks and their underparts show very little if any noticeable contrast. Western Willow Flycatchers often look a bit darker on the upper flanks and sides of the upper breast. Further, aside from the smaller and yellower below Pacific-slope and Cordilleran Flycatchers, other adult western Empids have fairly crisp and comparatively thinner white or whitish wingbars; fall immatures typically have broader and buffier terminal edges to their wing coverts. Adult Western Willow Flycatchers have broader buffy to grayish-tan wingbars.
Another similarity between Western Wood-Pewee and Willow Flycatcher is head profile. Both species have longer bills and more peaked hindcrowns than the other Empids. All Empids can show a peaked hindcrown, particularly when alarmed, but in general Empids are more round-headed than wood-pewees.
In the absence of hearing one of these birds vocalize or having mastered the subtle differences in shape and color, there is one fail-safe method for separating Western Willow Flycatcher from Western Wood-Pewee and that is overall wing length and primary projection.
The Contopus flycatchers (pewees, wood-pewees, and Olive-sided Flycatcher) have much longer wings than Empidonax flycatchers. Further, they have very long primary projection–the distance that the folded outer flight feathers (primaries) extend beyond the folded inner flight feathers (secondaries and tertials).
In general, Western Wood-Pewees are darker and browner above than Willow Flycatchers. Willows usually look somewhat warmer in overall tone and have some greenish cast to the upperparts, but that is highly dependent on lighting. Western Wood-Pewees are also more strongly vested below, but again this varies considerably depending on lighting conditions. Willows are paler below and usually look less vested and the pale yellow below is more extensive, usually covering most of the lower belly. As a rule, the lower mandible of a Willow Flycatcher is brighter yellow or yellow-orange and often shows no dark on the tip of the underside of the bill. The lower mandible of Western Wood-Pewee is usually a darker fleshy-orange with some dark near the tip. Willow Flycatchers may appear to have a weak eyering, something not seen on a Western Wood-Pewee.
Given the subjective nature of the plumage differences between Willow Flycatchers and Western Wood-Pewees, I would encourage you to first key in on the obvious structural difference in the wings of these two species. Once you gain a handle on that, their more subtle differences in color and behavior will likely become more noticeable.