Large prey for a small predator: Black-thighed Falconet Microhierax fringillarius preying on Black-capped Babbler Pellorneum capistratum

Restricted to Southeast Asia from the Central Himalayas eastwards, the Falconets of the genus Microhierax are the smallest of all birds of prey (White et al. 1994). Of the five species in the genus, only the Black-thighed Falconet Microhierax fringillarius has been recorded in Indonesia (Sukmantoro et al. 2007; MacKinnon et al. 2010; Irham et al. 2012). Measuring a mere 14-17 cm in total length (White et al. 1994) this species feeds mainly on insects, including moths, butterflies, dragonflies, alate termites, cicadas, orthopterans and beetles. However it is also known to sometimes take small birds such as munias and sunbirds, and occasionally lizards (White et al. 1994; Ferguson-Lees & Christie 2001; Wells 2007). In west and east Java none of the 50 or more stomachs examined by Bartels (1915-1931) contained avian remains, but remains of a small bat were found in a female’s stomach, and a prey transfer involving a small tree lizard was observed. In Central Java, Verbeek (1938) described the stomach contents of four Falconets, only one of which contained some bird feathers. H.J.V. Sody (in Becking 1989) lists three bird species as prey: White-capped Munia Lonchura malacca (= L. ferruginosa), White-headed Munia L. maja and Barn Swallow Hirundo rustica. In Baluran National Park, East Java, one was observed eating a Cave Swiftlet Collocalia linchi (Winnasis et al. 2011). Here we describe an observation of a Falconet preying on a bird that is unusually large relative to its own size.