By Matt WalkerEditor, BBC Nature
Crucial new discoveries about one of the world's least-known and rarest birds have been made by scientists.
The blackthroat, or blackthroated blue robin (Calliope obscura) is one of the world's rarest "robins", being known from only a handful of records since it was first described in the 1890s.
In 2011, experts resighted a small number of male blackthroats in China.
Details of the discovery are published in the Journal of Ornithology.
The species was first observed in 1886 in Gansu province, north west China.
The blackthroat is closely related to another of the world's most enigmatic birds, the firethroat (pictured below).
The firethroat is also a type of robin, or 'chat' - small slender songbirds related to the thrushes.
It inhabits similar forests in China, and has also been spotted in Myanmar, Bhutan and Bangladesh.
As the names imply, male blackthroats have a black throat, breast and side of the head, whereas male firethroats have a striking red throat and breast, referred to as a 'shining'.
A 2013 study by Prof Alström and colleagues confirmed that blackthroats and firethroats are separate species.
Songs of both species can be heard below.
In the late 19th and early 20th Centuries, about 10 individuals were collected at two locations in Shaanxi and Gansu provinces between May and August, during what was thought to the bird's breeding season.