GEOGRAPHIC, ECOLOGICAL AND SUBSPECIFIC VARIATION IN THE SONG OF THE RUFOUS-BROWED PEPPERSHRIKE (CYCLARHIS-GUJANENSIS)

We describe the patterns of song variation in the Rufous-browed Pepper shrike (Cyclarhis gujanensis). Individual variation was estimated usin g a sample of 659 songs belonging to 21 individuals. This analysis sho wed that this species uses a repertoire of up to seven song types. Geo graphic, ecological, and subspecific patterns of variation were estima ted using four songs from each of 93 birds recorded from Mexico to Arg entina. On each sonogram we measured 10 temporal, frequency, and struc tural features of the song. Principal component analysis based on the correlation matrix of these data showed that subspecies sing similar s ongs. However, there were significant relationships between principal component values and latitude, indicating that songs from equatorial a reas are shorter in duration, have higher maximum frequency and number of syllables, broader bandwidth and are less repetitive than those fr om more temperate areas. In addition, we classified the recording site s into three categories according to the actual vegetation: open, mixe d, and closed. A multivariate analysis of variance after removing the effect of latitude and altitude, showed that habitat types differ in s ong structure. Songs from open and mixed areas have a narrow bandwidth , and a lower maximum, minimum and emphasized frequencies than those f rom closed sites. We analyzed these patterns according to the current ideas about sound propagation in natural environments and the geograph ical pattern of body size variation in the Rufous-browed Peppershrike.