Flight order does not influence individuals’ flight initiation distance in small bird flocks

Researchers often measure the flight initiation distance (FID) of a selected individual to represent the FID of the whole groups which may vary with their flight order (the sequence to flee) and their spatial position within a group. In this study, we examined FID of all individuals in small bird flocks in urban environments when approached by an investigator. We found that individuals’ FID did not vary with their flight orders within these flocks. Moreover, the FID of the nearest individual, often used as a proxy for the entire flock, did not differ from the average FID of all flock members. This suggests that the conventional method of measuring the nearest individual’s FID to represent is a valid approximation for representing the behaviour of the entire flock in similar contexts. These results have important implications for understanding anti-predator strategies in group-living animals and can inform future studies in this field.