Can breeding bird density influence vocal individuality in bird song?

Abstract

Individuality is defined as the characteristics that determine the differences from one individual in species from another individual of the same species. Many animals use acoustic signals to communicate. These signals send messages about territorial defense, mate attraction and kin-ship. The ability to recognize who is singing is important for neighbor-stranger discrimination. Discrimination is also important if a species lives in a group or in colonies. It has been shown that there is a relationship between social group size and individuality both in rodents and many swallows. However many bird due not live in social groups but breeding bird density could also drive the evolution of individuality. We hypothesized that bird density will influence vocal individuality. We recorded 10 male birds from each of the following species; Green Tailed Towhees, House Wrens, Lazuli Buntings that sang 20 songs. Point counts in six open meadows and aspen patches were taken to measure density. These where then analyzed in Pratt acoustic software were various measurements of species were analyzed. The data was then analyzed with Beecher’s information statistic to determine individuality. We found that larger- bodied - bird species were less dense. We found a positive ship between breeding bird density and individuality but data were insufficient to reach significance. With a larger sample we may be able to suggest that bird density does influence vocal individuality in bird song.