Human Distance and Birds: Tolerance and Response Distances of Resident and Migrant Species in India

Abstract

In this report we describe a method of examining the tolerance of birds to humans, namely by measuring the distance to which birds will allow a person to approach them before flying off (flush distance). We studied the tolerance of Indian birds to approaching people by recording the flush distance for 925 individuals of 138 species of residents (birds breeding in India) and migrants (birds that are not known to breed in India). Over 20% of the variance in flush distance was accounted for by the number of people situated within 50 m, the distance to the closest person, the bird's migratory status, the number of people approaching, the time of day, and the bird's total body-length (including tail).For migratory species, 43% of the variability in flush distance was accounted for by distance to the closest other person, time of day, number of people originally within 50 m, number of people approaching, flock size, and species size. For resident species, only 18% of the variance was accounted for by distance to the closest other person, number of people within 50 m, and number of people approaching. Migrants were thus more responsive to the effect of humans, and their response was also influenced by their own size (body length) and flock size. Migratory species were less tolerant of people, flushing sooner than residents, and being more sensitive to the number of approaching people.We suggest that resident birds in North India have become habituated to the non-violent protective behaviour of the Hindu people towards birds, whereas migrants from farther north are more wary. Alternatively migrants, being less familiar than residents with the local predators and hiding places, may be more wary than residents on their home territory. Enhanced wariness results in more time spent alert or fleeing, with resultant greater energy-demand and decreased time for feeding.