Factors influencing the flush response and flight initiation distance of three owl species in the Andaman Islands

Abstract

Effects of anthropogenic pressures on birds of the Andaman Islands have been documented to some extent, however studies on the effect of human activities on the behavioural response of these birds are limited. This study assessed the anti-predatory behaviour (flush response - FR and flight initiation distance - FID) of three owl species (Otus sunia, Otus balli, and Ninox obscura) in response to human stimuli and factors influencing it on the Andaman Islands. In total, 63 % of owls flushed from their roost sites in response to approaching human, and such a response varied between species. Similarly, FID varied widely among the species ranging from 4.23 to 6.73 m. The FR of N. obscura was influenced by the count of climbers, presence of spine, and branch status, while roost height, ambient temperature, and lower count of climbers contributed to a higher FID. For the two Otus species, camouflage and pairing were found to influence their FR while FID of O. balli was influenced by roost height, pairing, and presence of spines. Our results indicated that the anti-predatory behaviour of owls on the Andaman Islands was species- and site-specific and prolonged disturbance to their roost sites may affect the survival and reproductive rate of these owls.

Where do the Tropical Owls Roost: Multiscale Habitat Variables Explain Roost Site Selection by Two Sympatric Otus Species in the Andaman Archipelago, India

“…We could not measure the anti-predatory behaviour of owls in response to non-human predators. However, experimental results showed that flush response and flight initiation distance of roosting owls decreased in response to approaching human stimuli when they roosted in well concealed spiny vegetation (Sureshmarimuthu et al 2021). Our results suggest thus, that on Andaman Islands, selection of roosting trees by the two Otus species may be shaped by predator avoidance, as birds select trees offering better camouflage and having spines.…”

“…Among the five species of owls known to occur in Andaman Islands, Andaman Scops-owl Otus balli , endemic to the Andaman Islands, is associated with evergreen-dominated patches, while the Oriental Scops-owl O. sunia (subspecies modestus ) is more widespread and common throughout the Andaman Islands (Babu et al 2019). Both species were reported to prefer to roost on the limbs of tree foliage in Andaman (Sureshmarimuthu et al 2021). Since the lack of knowledge in the differential roost site requirements of these sympatric tropical owls and the ongoing threats on these Islands, in this study, we aimed to identify the factors that influence the summer roost site selection of the two sympatric Otus owl species through a multi-scale approach (at the roost tree, roost patch, and macro scales) in the mosaic habitats of the Andaman Islands.…”