Vocal Activity Patterns of the Changeable Hawk-Eagle (Nisaetus cirrhatus) in Peninsular Malaysia during Mid-Breeding Season

Abstract

Vocalization in birds serves an important role in territory establishment and mate attraction as well as maintaining conspecific interactions and providing signals pertaining to food or threat. In Malaysia, most raptor behavioral studies on vocalization have been carried out on nocturnal raptors. Such studies have often been limited by the difficulty of accessing habitats where forest species reside and by raptors' elusive behaviors. We assessed the vocalization and vocal activity patterns of a common diurnal raptor, the Changeable Hawk-Eagle (Nisaetus cirrhatus), in an isolated lowland forest reserve, the Ayer Hitam Forest Reserve in Selangor, Malaysia, in mid-April 2021. Automated bioacoustics recorders were placed for 5 d in four different sites to passively collect the hawk-eagles' vocalizations. We recorded 480 hr of calls over the 5 d and the Changeable Hawk-Eagle uttered at least seven call types, with peak and longer call events at midday (1100 H and 1200 H, respectively). Calls were heard from 30 min before sunrise (0600 H) until shortly after sunset (1900 H). Call type 1 was by far the most common call type (2738 calls over 5 d) and was uttered throughout the day, possibly during flight and when perched. Other call types were uttered from late morning (1000 H) with exception of call type 3, which was uttered earlier (0900 H). Our findings may help provide improved raptor survey methods as well as fill the knowledge gap for diurnal raptor vocalizations in Malaysia.