The Bonin grosbeak or Bonin Islands grosbeak is an extinct finch. It is one of the diverse bird taxa that are vernacularly called "grosbeaks", but it is not closely related to the grosbeaks sensu stricto. Many authorities place the species in the genus Carpodacus, but some place it in its own genus, Chaunoproctus. A 2013 genetic analysis found it to be a relatively basal member of the group, more derived than the common rosefinch, but with no close relatives, with an estimated divergence time from other members of the group around 12.5 million years ago.
Region
Northwest Pacific (Ogasawara Islands)
Typical Environment
It inhabited oceanic island habitats including evergreen woodland, coastal scrub, and forest edges. The species likely favored areas with abundant fruiting shrubs and seed-bearing trees. As an island resident with limited predators before human arrival, it was probably rather tame and sedentary. It foraged both on the ground and in low to mid-level vegetation.
Altitude Range
Sea level to 300 m
Climate Zone
Subtropical
Ease of Keeping
Beginner friendly: 1/5
Also called the Bonin Islands grosbeak, it was an insular finch with an exceptionally thick, iron-strong bill adapted to hard seeds and fruits. Long debated taxonomically, it has been placed in Carpodacus or its own genus Chaunoproctus; genetic work suggests it was an early-branching rosefinch with no close living relatives. It vanished soon after human settlement of the Bonin (Ogasawara) Islands, with last reliable records in the 1830s, likely due to introduced predators and habitat change.
Restoration by Keulemans
Temperament
tame and sedentary
Flight Pattern
short rapid wingbeats with low, direct flights
Social Behavior
Likely occurred in pairs or small family groups, especially outside the breeding season. Nests were probably placed in shrubs or small trees, as in other rosefinches. Courtship and territoriality were presumed modest, consistent with island birds that experience limited predation pressure.
Migratory Pattern
Resident
Song Description
A simple, mellow finch-like warble interspersed with soft whistles and chips. Calls were likely low, contact-like notes used to keep in touch within small groups.
Plumage
Plain, slightly streaked brown to olive-brown upperparts with paler, buff-washed underparts; overall drab with minimal contrast.
Diet
Primarily consumed hard seeds and fruits from native shrubs and trees, using its powerful bill to crack husks. It likely took buds and flower parts seasonally when seeds were scarce. Occasional small invertebrates were probably eaten opportunistically, providing protein during breeding.
Preferred Environment
Foraged in coastal thickets, forest margins, and secondary growth where fruiting and seeding plants were abundant. It fed on the ground and at low to mid canopy levels, moving slowly and methodically.
