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11 March 2015 Boldness and urban dwelling in little ravens
Aaron Vines, Alan Lill
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Context . To successfully inhabit urban environments, birds must cope with the presence of people and vehicles at high densities. One hypothesised component of such coping is a high level of boldness, which may be inherent in all, or a particular subset of, species’ members as the result of natural selection or achieved through phenotypic plasticity allowing rapid behavioural adjustment to human disturbance.

Aims . To determine how much bolder urban little ravens (Corvus mellori) are than exurban conspecifics. To determine whether urban little ravens vary in their boldness as a function of local pedestrian and vehicular traffic volume, an important issue with respect to adjusting to the urban environment that has received little attention.

Methods . We assessed the relative boldness of free-living urban and exurban little ravens using the Flight Initiation Distance (FID) paradigm. The boldness of urban little ravens was also tested by measuring the reaction of individuals in areas with varying traffic volumes to a potentially startling sound stimulus (PSS).

Key results . On average, exurban ravens approached by a researcher had FIDs nearly 6-fold longer, escaped 1.4 times more by flying and fled >10 m 3.4 times more than urban conspecifics. Urban ravens in areas with varying pedestrian and vehicular traffic volumes had similar FIDs and mostly reacted similarly to a PSS, although retreat behaviour from a human and the PSS was influenced by traffic volume.

Conclusions . Boldness seems to be important in facilitating urban dwelling by little ravens. Antipredator behaviour did not appear to be strongly adjusted to local variation in traffic volume within the urban environment, but the reason for this is unknown. Further research with more extensive traffic surveying could help to answer this question.

Implications . The results are consistent with little ravens’ urban boldness occurring through initial urban settlement by a bolder subset of individuals. The importance of boldness in coping with traffic should feature more prominently in urban boldness research.

© CSIRO 2015
Aaron Vines and Alan Lill "Boldness and urban dwelling in little ravens," Wildlife Research 42(7), 590-597, (11 March 2015).
Received: 29 May 2014; Accepted: 3 December 2014; Published: 11 March 2015
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