The white swamphen (Porphyrio albus), also known as the Lord Howe swamphen, or white gallinule is an extinct species which lived on Lord Howe island, east of Australia. First encountered in 1788 and 1790 by British shipcrew.
Apparently the chicks were black, becoming blue and then white as they aged. This might have been progressive greying of the feathers.
Not much is known of this species, it was quickly driven to extinction by humans killing them with sticks (brutal, I know, sorry for that image!). They were already extinct before the island was settled in 1834. They would not have survived later either, since carnivorous animals were introduced to the island (rats and cats).