Javan Owlet Glaucidium castanopterum Scientific name definitions

23–25 cm; no data on body mass (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). Largish owlet with no “false eyes” on nape, indistinct facial disc barred with rufous and orange-yellow; eyebrows white; head brown with fine pale orange-yellow barring; upperparts uniformly rufous-chestnut, scapulars edged with broken white line; wings and tail barred orange-yellow and brown; upper breast barred rufous-brown; center of breast, belly and flanks whitish with bright rufous-chestnut streaks; irides yellow; cere olive-green; bill pale greenish-yellow, brightest at tip; feet yellowish to greenish-yellow (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). No other owlet within range.

This and some other Old World owlet species placed in genus Taenioglaux by some recent authors (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close , 2 Mikkola, H. (2014). Owls of the World. A Photographic Guide. 2nd edition. Firefly Books, Buffalo, NY, USA. Close ). Possibly closest to G. cuculoides, with which formerly treated as an isolated race. Monotypic.

Java and Bali.

Dense primary and secondary forest, from lowlands to c. 900 m, in some areas (e.g. Mt Papandajan (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ) ) up to  2000 m. Also coastal forests, dense stands of bamboo and occasionally gardens and villages (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Presumably resident (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Feeds mostly on invertebrates such as beetles, grasshoppers, crickets, mantids, cockroaches, spiders, scorpions and centipedes (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ); less commonly takes mice, small birds, snakes and lizards. Mainly nocturnal, but sometimes active by day. Hunts from perch, pounces on prey.

Male’s vocalisation a series of short trills  that drop in pitch and increase in volume as the song progresses, the song stopping at maximum volume; given at dawn and dusk. Food-begging calls of young, a high-pitched “tjeet tjeet tjeet” given day and night (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ).

Little information available. Breeding occurs from at least Feb–Apr; two "slightly incubated" eggs collected in W Java on 4 Mar 1927 (3 Becking, J.-H. (2009). The Bartels and other egg collections from the island of Java, Indonesia, with corrections to earlier publications of A. Hoogerwerf. Bulletin of the British Ornithologists’ Club 129(1):18–48. Close ). Nests in natural cavities and cavities made by woodpeckers and barbets (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ); clutch size 2; mean size of 8 eggs 33·5 mm × 29·5 mm (1 König, C., F. Weick, and J.-H. Becking (2008). Owls of the World. Second Edition. Christopher Helm, London, UK. Close ). 

Not globally threatened (Least Concern). CITES II. Considered rare to locally common in forest fragments and hills. No global population estimate, and little information available on general ecology. Tolerance of human activities may be similar to those of G. cuculoides; clear need for information on biology, habitat needs and population trends. Habitat loss probably the main threat.