Archilochus Hummingbird ID Analysis

by David Seibel

Below is a photographic analysis of a bird initially thought to be a "female-type" (female or immature male) Black-chinned Hummingbird, Archilochus alexandri, illustrating some of the challenges of separating this species from the very similar plumages of the Ruby-throated Hummingbird, Archilochus colubris. In the author's opinion the bird is clearly the latter species, which is by far the more common in eastern Kansas, where the bird was observed.

All of the photos below were taken by the author with a Nikon CoolPix 4500 (4x maximum optical zoom) mounted on a Kowa TSN-824 82mm spotting scope (20x) on 20 August 2003 in Art Swalwell's yard in Overland Park, Johnson County, Kansas. A bird suspected to be a Black-chinned Hummingbird (BCHU) had been seen daily in Swalwell's yard since 11 August 2003. Several photos had been taken between 11 and 20 August, but none allowed conclusive identification.* The bird depicted below was one of at least two, and possibly as many as four, female-type Archilochus hummingbirds making infrequent visits to Art's and his neighbor's feeders between 11:15 AM and 4:00 PM CDT on 20 August. Of those individuals, this one most nearly resembles a BCHU.

On previous days several observers, including the author, had watched a supposed BCHU, comparing it directly with nearby Ruby-throated Hummingbirds (RTHU), and collectively or individually noting all of the usual field marks and behaviors thought to identify female-type BCHU: grayish crown; dull grayish-green back; relatively pale auricular patch contrasting little with the throat; long, slightly decurved bill; slender head and neck (seemingly even more so than in RTHU); squarish tail extending only slightly beyond the wingtips when perched; wingtips broad, strongly curved, with apparent club-shaped tips of the outer primaries; tail pumping when hover-feeding (with the bill inserted into a flower or feeder, not just when adjusting position); and wing flicking between sips while perched on a feeder.

From subtle differences in photographs, it now appears that observers at various times might have mistaken multiple individuals, possibly even different sexes, as a single putative BCHU. Although it is possible that the bird analyzed below had not even been seen previously, it looked similar enough that both Swalwell and the author believed it to be "the" likely BCHU for several minutes, at least until a second suspect appeared briefly at the same feeder. Photographs of the second and all other hummingbirds observed on 20 August are readily identifiable as RTHU; the bird pictured below warrants a bit more analysis. (All five photos below are of the same individual, watched continuously between shots.)

*Hummingbird expert Nancy Newfield examined two photos taken by Art Swalwell and surmised, after careful study, that they were probably an immature male RTHU. See her discussion here.

Photo #1: Suggestive of a BCHU are the apparently broad tips of the primaries (numbered in the inset), grayish crown, very slightly decurved bill, and seemingly shorter tail than in a RTHU. Conversely, suggestive of a RTHU, the back is bright green and the auriculars contrast fairly strongly with the throat. Also note the buffy edges of the dorsal body feathers, indicating that this is a juvenile bird. The bill length seems adequate for a juvenile male BCHU, although at this point the sex had not been determined. (Troy Gordon, a hummingbird bander in Columbia, Missouri, wrote to say that the outer web of P6 would be narrower, and the feather more sharply pointed, in a male RTHU; he believes this to be one of the most reliable characters for sexing the species. Therefore, the bird would definitely be a female if it were a RTHU. According to Gordon, P6 shows a similar but much less diagnostic pattern in BCHU.)

Photo #2: The wingtips of the same bird photographed just seconds earlier appear much narrower, although this was not obvious at the time and would probably have been overlooked without the photo. Note the acutely angled tips of the outer primaries, especially the pointed P10. This effectively rules out BCHU if accurate, but seems puzzlingly at odds with the first photo.

Photo #3: When the bird flew up and perched on a branch above the feeder, the wingtips were at a better angle for photographic analysis, although the details were again not obvious through binoculars even at fairly close range (less than 40 feet). The bird's right wing was resting loosely at its side and appeared quite broad at the tip. However, in the photo, backlighting through the translucent feathers elucidates the three outer primaries' shapes (see inset) and effectively rules out BCHU. Note especially the long, narrow tenth primary.

Photo #4: Analysis of the left wing with reflective lighting. Again, the shapes of the outer primaries reinforce the identification as a RTHU. Sheri Williamson, author of Hummingbirds of North America (Peterson Field Guides, 2002), was kind enough to offer additional analysis of the tail, helpful in determining the bird's sex and age: Note the rounded tip to the outermost rectrix (R5), the broad white tip on R3, and the narrow white tip on R2. According to Williamson, who lives in Arizona, these characters typify immature females of both species of Archilochus, which tend to show more rounded tips to R5 than immature males and more white in the outer 3-4 rectrices than either immature males or adult females. (See plates 20-21 and 26-27 in the Peterson hummingbird guide.) In Missouri, on the other hand, Troy Gordon (pers. comm.) de-emphasizes the tail pattern in sexing young RTHU because of its extreme variability until the birds molt into definitive (adult) plumage.

Photo #5: When the bird turned toward the light and extended its tongue, the camera captured what appeared to be a gorget feather, previously hidden beside the base of the bill. The ruby-red color led the author to conclude - erroneously - that the bird must be a juvenile male RTHU, as the upper edge of the gorget would of course be black in a male BCHU (hence "Black-chinned"). But the adult male RTHU also has a narrow band of black across the chin, so that a feather in the position shown would be black in either species! Sheri Williamson (pers. comm.) believes the red spot on this bird is bare skin, "not an unusual occurrence given these birds' penchant for brawling." The lightly marked throat is also consistent with female plumage. With the help of Williamson's and Gordon's enlightening comments, this bird can now be identified with confidence as a juvenile female RTHU. (Considering the tortuous path to this conclusion, one disposed to anthropomorphism might think the bird's extended tongue is more than a coincidence!)

Thanks to everyone who gave input on this analysis. Special thanks to Art Swalwell, Tom Shane, Sheri Williamson, and Troy Gordon for helpful discussions, comments, and corrections to the web page, and to Bob Fisher and Nancy Newfield for related correspondence.