Song Variation in a Population of Mexican Juncos

The songs of 63 male Mexican Juncos living together in the same population, in Durango, Mexico, proved to be very variable in many characteristics. The average duration is 1.63 ± 0.29 seconds. The number of syllable types per song pattern usually ranges from two to five. Syllables average 0.137 ± 0.087 second in duration, with the first in the song tending to be longer than those which follow. Some syllables are given singly, others are repeated in trills. The position of the trilled parts of the song, of which there are usually two, sometimes one or three, is very variable. The average number of syllables per song is 10.1 ± 2.9. Most of these occur in the trills which make up the greater proportion of the song, and are the most regular component. The frequency characteristics vary widely. There are no systematic changes in loudness or in tempo through the song, except for a tendency for the first trill in the song to have fewer, longer syllables than those which follow. The individual notes from which the syllables are built up have a wide variety of forms. The species-specific qualities of the songs of this population of Mexican Juncos are less definite and stereotyped than in some other emberizine finches.