SOCIAL INFORMATION AND BIOLOGICAL INVASIONS: CHORUS SONGS ARE MORE ATTRACTIVE TO EUROPEAN STARLINGS IN MORE RECENTLY ESTABLISHED POPULATIONS

Abstract

ABSTRACTWhen biological invasions by animals occur, the individuals arriving in novel environments can be confronted with unpredictable or unfamiliar resources and may need social interaction to improve survival in the newly colonized areas. Gathering with conspecifics and using social information about their activities may reveal the location of suitable feeding and breeding sites. This could compensate for the absence of individual information about new habitats and constitute an advantage for new settlers. If a tendency to gather in response to social stimuli is transmitted from one generation to the next, and if the benefit of gathering is lower in long time established populations, there should be behavioural differences in receptivity to social cues in populations with different colonizing histories. We hypothesized that individuals of a social species like the European starling from relatively recently-established populations would be more responsive to social cues than individuals belonging to long-established populations. We conducted playback experiments using a starling chorus to test its acoustic attractiveness to populations of starlings with different colonizing histories. We compared the reaction of individuals from two populations in rural Brittany, western France, established for a long time, with three more recently settled ones: two populations from a propagation front in southern Italy and one urban population from Rennes city in Brittany. Our data supported our hypothesis: individuals from more recent populations were more responsive to the acoustic stimulus, and gave more calls in flight than individuals from populations with an older settlement history. We discuss the different behavioural responses we observed in the different populations and the potential effects of habitat characteristics and starling densities.