The northern boobook (Ninox japonica ) belongs to the family Strigidae (true owls) and is a raptorial owl endemic to eastern and southern countries of Asia. The species was considered, until recently, a conspecific of Ninox scutulata or brown boobook, a species of similar distribution encompassing 11 subspecies. The species currently includes two subspecies, the migrant Ninox japonica japonica and the non-migrant Ninox japonica totogo. Despite being considered as the most common breeding owl in Japan, little research has been conducted on the species and subspecies and the taxonomic classification of N.j.togoto and N.j.japonica has been a subject of debate. There are no indications of significant decline in northern boobook populations and therefore, its conservation status has been classified as least concern by the IUCN Red List.
Ninox japonica is a hawk owl species with a body length averaging between 29 and 33 cm and a wingspan of approximately 60 to 70 cm wide. Current knowledge on the species shows no sexual dimorphism and an average weight of approximately 168g. The northern boobook has a hawk-like appearance and its subspecies are practically undistinguishable. Individuals of the species will have a brown back and wings with lighter brown horizontal streaks on the tail feathers. The neck, crown and face of this bird are slightly more greyish brown aside from a small white patch above the beak. It has striking yellow gold eyes, a black beak and yellow talons. Its belly is almost completely white aside from rust-colored specs, which bare similarity to its sister species the brown boobook (N. scutulata ). Aside from mitochondrial distinction, research has determined that subspecies of Ninox japonica, N. japonica totogo and N. japonica japonica, can be differentiated through the shorter wing chord (214-217mm) and the longer tail (118mm) of N. totogo. This has been hypothesized to be an adaption due to the migratory nature of N. j. totogo.
Its habitat mainly consists of low altitude deciduous forests with thick vegetation and it will typically create its nest within trees, where they are practically indiscernible. These boobooks are also rarely seen reusing their nesting sites. These birds have also been identified in wooded parks, gardens and residential areas. They will typically winter in rainforests south of their summer home range and can occasionally be found in mixed or coniferous forests.
Siberia and most of Southeastern Asia make up the geographical distribution of Ninox japonica. The migrant N. j. japonica will occupy the majority of this range, whereas N. j. totogo will inhabit the Ryukyu Islands and Taiwan year-round. Specifically, Vietnam, Malaysia, Thailand and the Philippines will be common wintering territories for N. j. japonica, and Southern and Central China, Korea, Japan and Siberia encompass its breeding and summering ranges. Both subspecies of N. Japonica have also been recorded to occasionally coexist in Taiwan.
The northern boobook species prey mainly on invertebrates and occasionally on vertebrate prey. Invertebrate prey identified were mostly insects and vertebrate prey were mainly smaller birds, with the rare exception of lizards and bats. The northern boobook has been described as a generalist in his foraging preferences. It is a nocturnal hunter that will spot its prey from its perch and swoop down to capture it in midair or from the ground.
Male northern boobooks of the subspecies N. j. totogo will begin to occupy their respective breeding territory as soon as January and they will have bonded with a female by February. During this time, boobook couples have been observed moving around together and vocalizing more frequently. This behavior will typically denote the period in which the birds copulate, persisting until the eggs have been hatched. Incubation will typically last around 28 days from early March to early April. Female boobooks will undertake incubation alone and will typically lay between 3 to 4 eggs. The juvenile birds remain in the nest for approximately 26 days before fledging, which occurs in May. The migratory northern boobooks, N. j. japonica, will not typically occupy breeding sites before April, and their breeding season will only last 4 months compared to that of N. j. totogo, which lasts for an estimate of 5 months.
There are no global trends of Ninox japonica population declines and its conservation status is of least concern according to the IUCN Red list. This being said, very little information is available on their population size across their geographic range.
