Often times, we can recognise the voices of people we know or our favourite singers. But does the same apply in the animal world particularly for many birds that regularly call and/or sing?
Weighing about 110 g, the Sunda Scops-Owl (Otus lempiji) is one of the six resident owl species under the same genus, most of which have cryptic coloration, secretive habits and live in wooden habitats. In December 2014, with the aid of a microphone connected to a digital sound recorder, a study was commenced to collect the calls of the Sunda Scops-Owl from two habitat types, namely an isolated forest and oil palm smallholdings located in the state of Selangor. The study aimed at analysing and differentiating the calls of individual birds so as to facilitate their survey and monitoring in the future.
Over a period of seven months, a total of 75 usable recordings were obtained from 12 birds, i.e. six birds from each habitat. By using a sound analysis software (Raven Pro 1.5, Cornell Lab of Ornithology, Ithaca), spectrograms of these recordings were produced and eight vocal parameters (start, end, lowest, highest, maximum frequencies; mean fundamental frequency; note duration and internote duration) were measured from each call note that was visible from the spectrogram.
Being most frequently heard, the territorial call of the Sunda Scops-Owl was monotonous comprising a continuous series of single notes, lasting 0.20-0.26 second each, uttered at an interval of 12 second on average. By statistically comparing the vocal parameters, it was found that individual birds can be distinguished based on their calls and the accuracy was up to 95%. Such a difference in vocalisation remained constant over a period of three months. This implies the feasibility of surveying and monitoring the owl based on vocalisation without having the need to see or catch them for research purposes.
Interestingly, there was also variation in vocalisations for birds coming from different study sites. This indicates geographic variation in calls of the two owl populations in Selangor. This study was the first that examined the vocalisations of an owl species in Malaysia and there is a great potential to apply the technique on other owl species, most of which are understudied and hard to be detected by sight. This article provides an overview of a longer research article published in Journal of Raptor Research (Volume 50, Number 4, Pages 379-390). PDF version of this article can be downloaded at yee_et_al._2016_-_journal_of_raptor__research_50
Chong Leong Puan, Ph.D.
Universiti Putra Malaysia
Listen to this owl by clicking on Sunda Scops-Owl’s Call (1)
[ Audio credit: Yee Siew Ann]