Variation in boldness and novelty response between rural and urban predatory birds: The Chimango Caracara, Milvago chimango as study case.

The study of traits that enable species to thrive in urban habitats is critical to a better understanding the evolution of urban ecosystems. Here, we examined variation in boldness, neophobia, and exploratory behavior in a generalist raptor, the Chimango Caracara, Milvago chimango, occurring in areas with different urbanization level. We also focused on the relationship between object exploration and neophobia in rural and urban population of this species. The results showed that birds from more urbanized habitats showed more tolerance to humans than rural raptors, without any effect of age and sex in this trait. Rural birds were also more neophobic and were slower to explore than urban raptors, though they dedicated a similar amount of time to exploring novel objects, indicating a non-correspondence between the speed to approach and contact these objects and the amount of exploration performed. Finally, we found a correlation between exploration speed and neophobia in rural birds, whereas for urban raptors this correlation was not observed. Our results show that urbanization not only influences the expression of risk-taking behaviors and novelty responses in the chimango, but can also modify the relationship between exploration and neophobia.

The role of habituation in the adjustment to urban life: An experimental approach with burrowing owls.

Birds exhibit variation in fear behaviour in response to an approaching human within and between species and across different habitat contexts. We analyze urban and rural burrowing owls' variation in risk perception along separate but consecutive days (Treatment 1) and risk perception within the same day (Treatment 2). Fear behaviour was measured as flight initiation distances (FIDs) and aggressiveness level when a pedestrian approached repeatedly to an owl individual. We predict that the attenuation in fear response along treatments should add support to the habituation hypothesis (decrease the response to a repeatedly stimulus after verifying that it is irrelevant) while consistency in behaviour might be indicative of a personality trait. We found that FID decreased for measurements made on both treatments in rural owls and also in urban owls for Treatment 2. These results are compatible with a habituation process. We found that aggressiveness remained invariable along treatments in both habitats suggesting that different mechanisms underlie these behavioural responses. Our results suggest that owls' risk perception to humans can be adjusted based on environmental risk perception and that individuals are able to recognize and learn when a stimuli stops being a threat.