Behavioral Syndromes Break Down in Urban Song Sparrow Populations

Animals in urban habitats face a number of unique stresses, including the necessity of dealing with high levels of human activity. Growing research suggests that: (1) inherent traits, as opposed to learned behavior, influence which species invade urban habitats, and (2) individuals exhibit behavioral syndromes that limit behavioral flexibility. As a result, perhaps only animals with inherently bold personalities successfully settle in areas of high human activity, and such animals may also exhibit correlated variation in other behavioral traits, such as territorial aggression. In this study, we examine boldness and aggression in several urban and rural populations of song sparrows (Melospiza melodia). We found that urban birds were both bolder toward humans and also showed higher levels of aggression. We found a correlation between boldness and aggression in all populations combined, but no correlation within urban populations. Our results agree with other recent studies of song sparrow behavior, suggesting that greater boldness and aggression are general features of urban song sparrow populations, and a lack of a correlation between boldness and aggression in urban habitats is a general phenomenon as well. Urban habitats may select for bold and aggressive birds, and yet the traits can vary independently. These results add to a small number of studies which find that behavioral syndromes break down in potentially high quality habitats.