The influence of noise, temperature, and humidity on hornbill behaviour in a zoo

Natural environmental conditions are often overlooked in the welfare evaluation of captive animals despite their significant impact. However, numerous studies have shown how factors such as temperature and relative humidity influence the behaviour of wild avian species, leading to reduced foraging, locomotion and increased call rates. Additionally, anthropogenic factors, such as noise, have been shown to affect the behaviour of captive birds as well. All the birds were relocated from Jurong Bird Park, Singapore, to the newly established Bird Paradise, Singapore. The aim of this study was to observe the behavioural responses of five hornbill species: great hornbill (Buceros bicornis), rhinoceros hornbill (Buceros rhinoceros), wreathed hornbill (Rhyticeros undulatus), black-casqued hornbill (Ceratogymna atrata), and crowned hornbill (Lophoceros alboterminatus) to noise, ambient temperature and relative humidity. The sound pressure levels (SPL), temperature, and relative humidity levels were measured, and the behaviour of nine individual hornbills was observed using an ethogram four times a day with 15-min sessions over one month. The results showed (1) the hornbills were significantly more active when noise increased and significantly less active when temperature increased; (2) there was a significant increase in resting in the hornbills as temperature rose and a significant decrease in resting when noise increased; (3) as humidity increased, the hornbills displayed significantly more self-maintenance behaviours. Noise was found to have a greater impact on active and resting behaviour than temperature. While anthropogenic influences do affect animal behaviour, natural environmental factors are often overlooked and should be incorporated into a comprehensive evaluation of animal welfare.