The call type variation and usages of the Eurasian tree sparrow Passer montanus

Bird call, which is widely used in all species of birds, is short, simple, and functionally diverse in comparison to song. Here, we have recorded call types of Eurasian tree sparrows (Passer montanus) at multiple situations and various communal behaviors. The Eurasian tree sparrow belongs to the oscine (song-learning) group of songbirds, but their calls are more developed than their song. The calls are used to communicate a variety of behaviors in their social flock. In this study, we categorized call types and usages in relation to the situation on the basis of visual categorization of spectrograms and descriptive measurements. Adult Eurasian tree sparrows have 9 call types (including 9 sub-types at A1 family) and chicks have one (including 2 sub-types). Each call type could be classified as A1 contact call, A2 Fight-intention call, A3 Aerial call, A4 Alarm/Anxiety call, A5 Emergency call, A6 Warning/Threat call, A7 Stimulate call, A8 Screaming call, A9 Social calling, and C1 Begging call. Our results suggest that the diversity of Eurasian tree sparrow’s call types is related to the complex social structure of the species, and might be associated to evolution of sociality. Further research on correlation between various call types and social behavior is needed to find social communication characteristics of Eurasian tree sparrows and other social weaver species with similar ecology may reveal whether evolutionary pressures of sociality lead to increased call complexity.