This huge blackbird is hard to ignore due to its boisterous nature. Polytypic. Length 15–18".
Long, deeply keeled tail. Large, thick bill, with nearly straight culmen. Flat crown; shallow forehead. Adult male: entirely black with obvious violet-blue iridescence. Eyes yellow; bill and legs black. Adult female: smaller than male. No keeled tail. Brown above with dull iridescence on wings and tail; buffy on head and below, becoming darker brown on belly and vent. Dark lateral throat stripes usually obvious. Eyes yellow. Immature male: smaller than the adult male, with shorter tail, dull iridescence, browner wings, and frequently dark eyes. Juvenile: like female, but paler and shows diffuse streaking below.
Eight great-tailed grackle subspecies are recognized, but only 3 are found in North America. These northern subspecies are prosopidicola, found in the east of the great-tailed's range west to central Texas; monsoni, found from central Arizona east to western Texas; and nelsoni, found in California and western Arizona. All 3 subspecies of the great-tailed are spreading northward in the United States. For the most part, there is little information regarding which subspecies have spread to which areas, therefore the range descriptions given above are tentative. And some intergradation may be occurring now that these subspecies are coming widely into contact.
The males of these subspecies are similar, differing mainly in size, with prosopidicola and monsoni being large subspecies while nelsoni is noticeable smaller. With regards to plumage gloss, but this is variable. Differences in plumage are much more marked in females. In general, monsoni females are darkest below, nelsoni palest, and prosopidicola intermediate, although closer to monsoni. In fact, nelsoni females may be pale grayish below with a nearly white throat; this coloration is strikingly different from the buff to warm underparts of prosopidicola and monsoni. The pale plumage combined with the small sets nelsoni well apart from prosopidicola and monsoni.
Historically, the mountains of central Mexico divided the general population of great-tailed grackles into an eastern and central group and a western group. The "western" great-tailed grackles, from nelsoni in the north, to coastal forms in west Mexico south to Guerrero, are small. They have a noticeably different song than the more eastern populations, and there are genetic differences. However, with the opening of more grackle-friendly habitats throughout the area due to agricultural and urban development, this previously isolated population has come into contact with eastern great-tailed grackles. In Arizona, integration between nelsoni and monsoni appears to be common, and birds that have monsoni mitochondrial DNA are by measurements small and like nelsoni.
The very similar boat-tailed grackle overlaps with the great-tailed grackle in southwestern coastal Louisiana and eastern Texas.
Call: a low chut; males may give a louder clack. Eastern males give a striking ascending whistle twooo-eeeeeeee! Song: the eastern bird sings a 4-part song beginning with harsh notes similar to the breaking of twigs, then an soft undulating chewechewe, and then twig-breaking notes and finally several loud 2-syllable cha-wee calls, crrrk crrrk chewechewe crrk cha-wee cha-weewlii. Subspecies nelsoni sings a repeated series of notes, ending in a more accented note chk-chk-chk-chap-chap-chap-chap-chweee, often interspersed with various other repeated notes.
Status and Distribution
Abundant. Year-round: open habitats with dispersed trees, from agricultural to urban. Migration: not well understood; more are wintering farther north now. Vagrant: casual to the north of its range, from British Columbia east to Nova Scotia.
The species has experienced a great range and population increase in the United States, showing a 3.7 percent annual increase from 1966 to 1998.
—From the National Geographic book Complete Birds of North America, 2006