(Sialia mexicana)
Summer
Year-round
Winter
HABITAT: Various open coniferous and mixed woodlands, especially ponderosa pine; also farmlands, orchards, and moderately logged areas
DESCRIPTION: Male is dazzling, deep, purplish-blue on head, back, wings, and tail; chestnut on breast and sometimes on back; grayish below with blue-gray belly; female more subdued grayish overall
Songless, as in “without song,” declared one authority in the early 1900s. “No, they sing,” rebutted another. What confusion, and how enlightening it is to understand the basis for the disagreement.
The story begins with the most commonly heard sound from these bluebirds, a simple call that is used throughout the day by both male and female. It’s a soft few, or kew, slurred down, just a tenth of a second long, often given in flight or when birds separate. (The bluebirds have several other calls, too, such as a chatter and a relatively harsh double note.) During the day, then, it seems that these bluebirds don’t really “sing.”
The naturalist who claimed these bluebirds do sing slept among them, documenting an extended vocal performance beginning as much as two and a half hours before sunrise! But even he concluded that the “song” consisted largely of a long series of rapidly repeated call notes, especially the few, that are used separately in different contexts throughout the day. Seventy-five years later, this conclusion is still passed on in some of our modern field guides: Western Bluebirds use call notes to “sing.”
But if you listen to one of those early morning singers yourself, you might come to a different conclusion. Slowing down the “few songs” on a computer reveals a wonderful variety of phrases that these earlier listeners missed. Yes, there are “few-like” notes that sound to the human ear like the daytime call note, but there are many other sounds, too. In one recording, you might hear eight different phrases in the first ten seconds, such as A B C D E F G C D E! He sings! There’s no doubt.
Male’s dawn song 
