Blue-Wattled Bulbul

The blue-wattled bulbul is a songbird in the bulbul family, named for the Dutch explorer Anton Willem Nieuwenhuis. It is rarely seen, and it is not clear whether it is a distinct species or a natural hybrid between the black-headed bulbul and the grey-bellied bulbul or other close relatives. Two subspecies are recognised: one now extinct and once found on Sumatra, and one found on Borneo. It is known only from two specimens collected in 1900 and 1937 and a few observations (Wikipedia, general species account).