Urbanization and social antipredator behaviour in American crows

Background/Question/Methods

Synurbic species tend to be generalists that benefit from living in close proximity with humans as they are capable of exploiting anthropogenic benefits that more specialised species cannot. Typical adaptations to living in urban areas include changes in foraging behaviour, increased intraspecific aggression, and tameness toward humans. The American crow, Corvus brachyrhynchos, are a highly urbanised species that have greatly increased in abundance in urban areas. While individual-level behavioural adaptations are an active area of research, adaptations of social behaviours in corvids are underexplored. Here, we ask if social adaptations might be one of the reasons why American crows seem to thrive in urban areas. Urban settings have been shown to alter the frequency of social foraging behaviour, such as sentinel behaviour, by lowering the risk of predation from natural predators (e.g. raptors), by increasing access to anthropogenic food sources (e.g trash cans and litter), or by providing novel sources of stress (e.g. noise/light pollution, feral/free-roaming pets). We performed experimental trials that consisted of supplemental feedings where the amount and quality of food varied. Sentinel behaviour in American crows was quantified and compared between urban and rural populations in the Niagara region.

Results/Conclusions

Preliminary analysis suggests that urban crows exhibit sentinel behaviour less frequently than rural crows, which could explain, in part, the crow’s success in urban areas. Changes in sentinel behaviour reflect the individual’s perception of their surroundings. If the costs incurred by the individual exceed the benefits from participating in social behaviour, then an individual can choose to forage in a more individualistic manner. By observing these changes, we might provide insights into how social behaviour can change in response to environmental influences. These findings could be important in understanding how species might respond to the rapid, global increase in urbanisation, and contribute to the existing literature on how social behaviour can benefit synurbic species.