The Western Bluebird— Carrying the Sky Above and Reflecting the Earth Below
At the wildlife rehabilitation center, I grabbed a dish of fresh mealworms and headed to an outdoor aviary.There, 11 hand-raised fledgling Western Bluebird orphans were honing their flying and foraging skills before release back into the wild. As I stepped into the aviary, I found myself enveloped by a cloud of blue as the youngsters swirled around the fresh food I had brought. I pivoted slowly and soaked in the deliciousness of the moment.
A small, portly member of the thrush family, a Western Bluebird’s head appears quite round; the body, somewhat humpbacked and potbellied. Western Bluebird males have gorgeous blue plumage on their heads, wings, and tails; rust-colored breasts; and, frequently, chestnut patches on their backs. Western females are muted pastel renderings of the males; immatures, even paler and speckled. They eat insects during the warmer months and switch to primarily berries and fruit (especially mistletoe) through the winter. They often sit conspicuously (e.g., on utility lines), wings stretching and tails flicking. Their call is a soft, down-slurred, single-noted “phew.” Their song is a halting series of chirpy notes, heard less frequently than the call and often only in the pre-dawn hours.
Western Bluebirds commonly reside in San Diego County’s foothills and mountains. Toward the coast, the species becomes less abundant and more localized; but it remains common in many places there, especially in northern San Diego County.
Bluebirds are secondarycavity nesters since their beaks aren’t strong enough to chisel out their own nesting cavities in trees. Instead, they rely on natural snags or holes excavated by primary cavity nesters such woodpeckers; they will also readily nestin nest boxes. In San Diego County,Western Bluebirds lay 2−6 eggs (average, 5)mainly from early April through the end of June; incubation lasts 12−14 days; both parents feed the young. Where bluebirds have more than one brood, as in San Diego County, juveniles from earlier clutches sometimes help to feed the young of later clutches during that season. Nestlings fledge about 21 days after hatching and stay with their families for several weeks afterwards.
The origin of the bluebirds’ names is an interesting and circuitous one. (Well, honestly, “bluebird” ‘isn’t all that interesting. I mean, just look at them.) Eastern Bluebird was the first bluebird assigned a genus/species name in the 1700s by Carl Linnaeus, the inventor of the binomial naming convention. Sialia is the Latinized plural version of the Greek word sialis, meaning “a kind of bird.” (Those Greeks really went in for precision labeling, didn’t they?) For some reason, Linnaeus gave the Eastern Bluebird this oddly pre-eminent species name; he then classified it in the Motocillia genus (primarily wagtails today). Later, when Eastern Bluebird moved to the thrush family and needed a new genus name, William Swainson simply adapted the species name to arrive at the redundant Sialia sialus. The closely related Western and Mountain bluebirds followed Eastern Bluebird into the Sialia genus. The Western’s species name,mexicana, reflects the fact that the first specimen was collected from Mexico, although the species can be found throughout the west (and, hence, the common name of Western Bluebird).
The Western Bluebird is in decline over much of its range, possibly as a result of the loss of nesting cavities to logging and fire suppression and from competition for cavities with European Starlings and House Sparrows. In San Diego County, though, despite many competitors for nest sites, the Western Bluebird appears to be holding its own and actually extending its breeding range. The spread of Nuttall’s Woodpecker into urban areas as a breeding speciesbroughta primary cavity excavator into an area that once had none. Westerns may also be adapting to novel local nest sites such as the crevices behind the leaf bases of certain species of palms and the gaps between the tiles of roofs.
As a friend of mine who has been a linchpin of the North American Bluebird Society says, “May all your blues be birds.”