Gerald Thayer wrote to Dr. Chapman (1907): “In its movements the Black-throated Blue is more deliberate than many of its relatives, but it has at the same time a somewhat Redstart-like way of ‘spiriting’ itself from one perch to another, and, while perched, of partly opening its white-mooned wings;—a habit and a marking shared by the boldly blue-and-black-and-white males and the dimly green and yellowish females and young.”
Henry D. Minot (1877) writes:
They are very dexterous in obtaining their insect prey; sometimes seizing it in the air, with the skill of a true Flycatcher, and at other times finding it among the branches of the various trees which they frequent. Now they twist their heads into seemingly painful postures, the better to search the crannies in the bark or blossoms, now spring from a twig to snap up an insect in the foliage above their heads, instantly returning, and now flutter before a cluster of opening leaves, with the grace of a Hummingbird. Occasionally they descend to the ground, and are so very tame that once, when I was standing motionless, observing some Warblers near me, one hopped between my feet to pick up a morsel of food.
Voice.—Aretas A. Saunders has sent me the following study of the song: “The song of the black-throated blue warbler, in its more typical forms, is one of only three or four slowly drawled notes in a peculiarly husky voice, the last note commonly slurred upward. While the number of notes in the songs varies in my 41 records from two to seven, more than half of them are of only three notes, and most of the others are of four or five. In all, 22 songs end with the upward slur of the last note, 14 in an unslurred note and 5 in a downward slur. The general trend of the pitch is upward in 29 records, downward in 10, and ending in the same pitch as the first note in 2.
“The pitch of songs varies from G‴ to E‴´, a range of four and a half tones. Single songs range from half a tone to three tones, the majority covering one and a half or two tones. The length of the songs is from 11⁄5 to 2 seconds. This indicates the slowness of the three or four notes, for other warbler songs with twice as many notes are about the same length. In the few songs of this bird that have more notes the notes are shorter and faster, so that the songs are not longer.
“This species shows a greater tendency to sing unusual songs than most warblers. On three occasions I have heard a warbler song that I could not recognize, and when I located the bird, found it to be a black-throated blue.
“Two of these songs were of rapid notes, in a clear, ringing quality, not at all like the ordinary song of this bird. The third was two rather long notes in a clear, sweet whistle, the second higher in pitch than the first, so that it resembled the phoebe whistle of the chickadee reversed.
“The average date of the last song in 14 summers in Allegany State Park is July 21. The earliest is July 14, 1927 and 1940, and the latest July 29, 1931. The song is rarely revived in August, after the molt.”
Francis H. Allen (MS.) writes the two common songs as “quee quee quee-e-e´” and “que-que-que-que quee-ee´,” and says further, “in June 1907, I heard a bird in Shelburne, Vt., that sang persistently a short song like kū quee-e-e´ besides singing occasionally one of the ordinary songs. In May, 1910, at Jaffrey, N. H., I heard a bird sing over and over qui-qui-qui-qui-qui-qui-qui-qui-quee´, but most of the birds of the region seemed to sing zee zee zee-ee, with a falling inflection, while some sang the ordinary quee quee quee-e-e´, with rising inflection. The quee songs have a nasal tone. The call note is a dry chut or chet, resembling the chip of the black-throated green but not so thick.”
Mrs. Nice (1930b) describes four different songs; and Gerald Thayer, in Chapman (1907), gives four main songs, with variations, but the versatility of this singer seems to be well enough shown in the previous descriptions.