Note: I am still trying to verify and sort some of this out, so don't consider it gospel (or anything else you find on the Internet that isn't peer-reviewed or from an official agency!)
Subspecies (distinguished by coloration and range) - name is preceded by Genus and Species (e.g., Sialia sialis grata). For description see (NABS) Bluebird, Winter 2003, Vol.25, No.1
Sialia sialis bermudensis
(Verrill, 1901)
Sialia sialis caribaea (Howell 1965)
Sialia sialis episcopus (Oberholser) - note BNA lists Sialis sialis sialis (Linnaeus 1758 which includes episcopus)
Sialia sialis fulva (Brewster 1885)
Sialia sialis grata (Bangs 1898)
Sialia sialis guatemalae (Ridgway 1882)
Sialia sialis meridionalis (Dickey and van Rossem, considered part of guatemalae by Webster 1930)
Sialia sialis nidificans (Phillips 1991)
No subspecies recognized.
Sialia mexicana amabilis (Townsend)
Sialia mexicana anabelae (Anthony, not on Phillips list)
Sialia mexicana bairdi (Ridgway)
Sialia mexicana jacoti (Phillips)
Sialia mexicana mexicana (Swainson)
Sialia mexicana nelsoni (Phillips)
Sialia mexicana occidentalis (Townsend)
Distinguishing Characteristics (Adult Male)
Red-brown throat and white belly
Pale sky- blue breast and flanks. Lacks distinct red coloration but may show a trace of rufous on throat and breast. Straighter posture/
Bright purplish-cobalt-blue on head, chin, throat, and tail. Brown breast and a gray-blue belly.
Distinguishing Characteristics (Adult Female)
Orange-brown throat and white belly with pale brown outline
Pale sky-blue. Pale chin? Grayer back? Ashy gray belly, may have rufous wash on breast.
Tend to have a brown abdomen and gray head, throat and back. Tails and wings gray-blue color.
Differences between Species (Sibley and others)
Like Western but smaller overall and slightly thicker-billed
Slimmer, especially longer-winged and tailed, thinner bill with little or no yellow at base. Males and females paler blue.
Stocky with rather short tail and wings, stout bill, large head. Darker underwing coverts than Eastern. Less vocal than EABL.
Size (Sibley)
Length 7", Wingspan 13", WT 1.1 oz
Length 7.25", Wingspan 14", WT 1 oz
Length 7", Wingspan 13.5", WT 1 oz.
Range
East of the Rocky Mountains, spanning from southern Canada to the Gulf states and on into Mexico and Honduras. Populations are found in Cuba, although it is not a native species there. (Terres, 1980)
Nests in the foothills and mountains of western North America, from east-central Alaska, east to southwestern Manitoba and the Dakotas, south to southern California, northern Arizona, and southern New Mexico. May winter as far south as Mexico, or as far north as British Columbia.
Throughout parts of western North America, including southeastern British Columbia, Alberta, Washington, Oregon, Idaho, California, Nevada, Utah, Colorado, New Mexico, Arizona, northern Baja California, and the central Mexican states. (Guinan, Gowaty, and Eltzroth, 2000)
Inter-breeding (rare in wild)
Interbreeds with Mountain
Hybridizes with both Eastern (Lane 1969, Rounds and Munro 1982, Steblay 1986) and Western (Aylesworth 1987)
Considered extremely rare although overlap exists with MOBL in part of range
Other Differences
Male may be more aggressive defending nest. Most migratory. Eggs are paler blue. Establish territories later than WEBL in areas where ranges overlap
Least migratory. Do not prefer large open meadows. Establish territories earlier than MOBL.
Recommended distance between nestboxes
100 yards minimum
200-300 yards
100 yards. 200-300 yards may be better
Nestbox Hole Size
1.5" round minimum
1 9/16" round minimum
1.5" round minimum
Nests
Seldom (or just a few) feathers, nest usually of grass and pine needles
May use twigs, rootlets, bark, and, sometimes, wool, hair, or feathers
May use feathers and trash, hair, thin bark, leaves in nest cup
David Allen Sibley, The Sibley Guide to Birds, November 2001
Native american names for bluebirds include: Chimalis or Chimalus, Chosovi (Hopi) - source: Spotted Wolf's Corner, Native American Names; Chimalus version from Indian Popular Names, from the Library of the University of California, L.A., E98 N2U5)
On this website, also see:
range maps and description of ranges for each species.
The bluebird is well named, for he wears a coat of the purest, richest, and most gorgeous blue on back, wings, and tail; no North American bird better deserves the name, for no other flashes before our admiring eyes so much brilliant blue.
- Arthur C. Bent, 1949
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Bluebird Names and Species 
