Survival and song-type sharing in a sedentary subspecies of the Song Sparrow

The extent and spatial pattern of song-type sharing amen neighboring males in one subspecies of Song Sparrow, Melospiza melodia cooperi, were examined in two San Diego County populations. Repertoire size averaged 9.6 song typ es per male (range 7 to 13). Song-type sharing was greatest between neighbo rs and declined with distance between territories. Adjacent neighbors share d an average of 22% of their song types. Variation in the amount of sharing between adjacent territory owners was high, ranging from 0% to 86% reperto ire overlap. Results are consistent with the expected pattern produced by a ge-restricted learners that attempt to establish territories near tutors. T he probability of a male surviving and remaining on his territory through t he breeding and nonbreeding season increased as the fraction of song types shared with adjacent neighbors increased. The amount of song type sharing m ay therefore be an indicator of a male's competitive ability to obtain a pr eferred territory near his tutors, or it may determine a male's effectivene ss in using shared and unshared song types to communicate aggressive intent ions.