Interactions between the Greater Racket-tailed Drongo Dicrurus paradiseus and woodpeckers in a lowland Malaysian rainforest

In tropical regions numerous bird species have been documented following mixed-species foraging flocks or other vertebrates and capturing invertebrates flushed by the movement of these animals. Such behaviour is thought to benefit the following species by increasing their foraging efficiency (Croxall 1976, Powell 1985, Rodrigues et al. 1994). Drongos (family Dicruridae) are medium-sized, often glossy black, insectivorous birds found in a range of habitats from Africa to Asia, Australia, and the Solomon Islands (Perrins 1990). Of the approximately 24 species of drongo, 17 have been documented associating with animal species ranging from ants to large mammals (Ali and Ripley 1987, Bannerman 1939, Beehler et al. 1986, Boonsong and Round 1991, Coates and Bishop 1997, Croxall 1976, Dickinson et al. 1991, Ganesh 1992, Greig-Smith 1978, Herremans and Herremans-Tonnoeyr 1997, Hino 1998, Jeyarajasingam and Pearson 1999, Mackinnon and Phillipps 1995, McClure 1967, Veena and Lokesha 1993, Willis 1983, Woodcock 1980, Zimmerman et al. 1996). For five species, observers specifically noted that these birds followed other animals to prey on arthropods and small vertebrates flushed by their movements. Studies in Africa and Madagascar have shown that rate of prey capture increased when drongos followed other species compared to when foraging alone (Greig-Smith 1978, Herremans and Herremans-Tonnoeyr 1997, Hino 1998, Veena and Lokesha 1993). The Greater Racket-tailed Drongo Dicrurus paradiseus is the most common drongo species resident in lowland forests in West Malaysia. It has been reported as an occasional participant in mixed-species flocks, but its role in these flocks and the species with which they commonly associate have not been identified. McClure (1967) classified this species as a passive, or nonfollowing, flock attendant, which suggests that it does not use other flock attendants as beaters. While studying the foraging ecology of woodpeckers in an aseasonal lowland dipterocarp rain forest at Pasoh Forest Reserve in West Malaysia (see Kochummen et al. 1990 for a description of the reserve and forest type), we noticed a frequent association among various species of woodpeckers and the Greater Racket-tailed Drongo. Subsequent to observing these apparently common associations, we followed every woodpecker or drongo seen or heard during the course of the field season and recorded the presence of other species and noted behaviour. We were thus able to determine the frequency with which Greater Racket-tailed Drongo and woodpeckers associated with one another and if certain species associated more frequently than others do. Of the 150 times woodpeckers were followed, Greater Racket-tailed Drongos were observed following them 76 times (50.7% of the observations). We followed drongos 16 times; 13 times (81.3%) they were seen associating with other species and 8 times (61.2%) with woodpeckers. The three times that drongos were seen alone they were in groups of 3 or 4, and were not actively foraging. For 20 additional observations it was impossible to distinguish whether the initial cue was from a woodpecker or a Greater Racket-tailed Drongo (for example, seeing a drongo and hearing a woodpecker tapping at the same time), suggesting that they may be associated more than 50% of the time. Some other animals that the Greater Racket-tailed Drongo foraged with less frequently were malkohas Phaenicophaeus, arboreal squirrels (Sciuridae), and leafbirds Chloropsis. While associating with woodpeckers, a drongo frequently perched within 5 m of the individual it was following, often below the bird on an open horizontal perch, and would periodically sally out near the Ambang Strict Nature Reserve, fairly close to the type locality, has also recently been found (Lee and Riley in press in BirdLife International 2001).