Living in Colorado, we had a pretty easy time identifying the four common hummingbird species. Sounds like a cricket flying by, showing bright red throat feathers? Broad-tailed. Slender, dark-headed with no rufous or buffiness anywhere? Black-chinned. So tiny that it has to stretch to reach the feeder port from the perch? Definitely Calliope. A shock of glimmering copper orange zipping noisily past and fighting with everyone at the feeder? Rufous. Pretty much no other likely options. Done and dusted.
Here in San Diego County, things get a bit trickier, especially within the Selasphorous genus. (Stick a pin in that. We’ll circle back in a bit.) Present year-round, flashing hot copper tempered by a cool green mantle, crown, and back, an adult male Allen’s Hummingbird (Selasphorus sasin)gleams like few other birds. His stunning, orange-red gorget(throat feathers) sometimes shines green or gold. Females and immatures are greenish above, paler below, and conspicuously washed with buffy orange on the sides, tail, and undertail. Theirpaler gorgets often show a smattering of bright reddish orange feathers, commonly clustered in the lower middle.
Allen’s Hummingbird has a remarkably limited distribution,breeding only in a thin strip along the coast of California and southern Oregon. Most hummingbirds breeding in the U.S. represent only one subspecies. Yetwithin its narrow range, two subspecies of Allen's Hummingbird occur:S. s.sasin and S. s. sedentarius. These subspecieslook very similar but have dramatically different migratory behavior. Sasin winters in central Mexico;sedentarius(the subspecies name says it all) doesn’t migrate, having recently expanded its breeding range from the Channel Islands southward into San Diego County (first found nesting at San Onofre in 2001). Here, they range between sea level and 1,000’ but always within the reach of the coastal fog.
As with all hummingbirds, males have no involvement in raising the young. This reality comes into sharp focus with the sexes’ respective breeding territories. Males opt for coastal scrub vegetation or riparian shrubs; females select nest sites in more densely vegetated areas with at least some tree cover. Nesting can stretch from late October through mid-July, producing as many asfour broods in a single season. The female almost invariably lays two eggs, as do other hummer species. Nest-building typically takes 7−11 days; incubation, 16−20 days. She perches on the edge of the nest, inserts her bill vertically into the open mouth of the nestling, and regurgitatesa slurry of food into the nestling's mouth with a rapid pumping motion. She typically feeds each nestling twice per visit; each individual feeding takes a mere 3−10 seconds. Leaving the nest 21−30 days after hatching, the youngsters continue to be fed by the female for another 10 days. Fledglings can be comical, frequently probing objects with no hope of nectar(e.g., brightly colored hats, yard decorations) while they figure out the world of nectar tubes.
Allen’s Hummingbird’s scientific namewaxes both poetic and historic. Selasphorous (“to bear a flame”) arises from Greek selas (“light, flame”) and phoros (“bearing”). The male’s iridescent gorget makeshim appear to be carrying a flame on his throat. Charles Andrew Allen, an amateur ornithologist, collected what was thought to be the type specimen around the Nootka Sound on the Pacific Northwest coast in 1877; taxonomists gave it the species name of (alleni) in his honor. But it turned out that this species had already been described in 1830, assigned the species name ofsasin—the Nootka Sound indigenous people’s (the Noo-chah-nulth) name for this bird. Taxonomy rules state that the earliest binomial name takes precedence.So Allen lost the scientific species name but retained the common name.
Back to the tricky ID issues. In shape, plumage, and temperament, the male Allen’s differs from his congener, the Rufous Hummingbird (Selasphorus rufus),only by feather-splitting degrees—so much so that they often can’t be confidently differentiated in the field. Looking at a hummer with a solid rufous back and head? Okay, that’s an adult male Rufous. However (wouldn’t you know it?), a small percentage of Rufouses can have green on their backs, including some with entirely green backs. Thus a green-backed adult male could be either an Allen's or a Rufous. Some solid clues do exist, though. At close range, look for a flared tail. Count one feather over from the middle pair of tail feathers (retrices)—known as R2—and check for a notch or indentation. See one? It’s a Rufous. Other, subtler differences exist; but they’re even harder to spot. And just to add to the fun, a zone of Allen’s x Rufous hybrids has recently been documented along the coast of southern Oregon and northern California. Female and immature Allen's are, in most circumstances, pretty much impossible to distinguish in the field from their Rufous counterparts.
The calendar offers a wee bit of help. The latest documented sighting of a male Rufous Hummingbird in San Diego County is May 19; most male Rufouses begin showing up again in early to mid-July. So, for six to eight weeks in summer, flying copper jewels are likely Allen’s.
Rather than sweat the details, though,how about just chalkingthe birdsup to “Selasphorus sp.”(birder jargon for ”undetermined Selasphorous species”)? Simply savor the beauty.