Western Polynesian Megapode (Megapodius alimentum)
The Megapodes, so called for their large feet used for digging, are characterized by their strange breeding behavior: they do not incubate their eggs with their body heat as other birds do, but bury them.
Some species lay their eggs in the sand of beaches, heated up by the tropical sun, some use volcanically heat for incubation, others collect as much decaying plant material as possible to build so called mounds, in which they then place their eggs.
Probably most islands in Melanesia, Micronesia, and Polynesia formerly harbored their own populations of Megapodes, numerous species are now known from subfossil remains. Some species, most of them considered hypothetical, are known from eggs only, or from contemporary eye-witness accounts.
The Western Polynesian Megapode, also known as Consumed Scrubfowl, was described in 1989, it is known from subfossil remains found on several islands of Fiji and Tonga.
The species was bigger than its living congeners, but by far not the biggest species, it was still volant and probably inhabited nearly all islands from the Fijian Lau group to the Tongan chain.
It disappeared after the colonization of these islands by the first Polynesian settlers, who not only hunted the adult birds but also dug up their eggs. 
 T. H. Worthy: The fossil megapodes (Aves: Megapodiidae) of Fiji with descriptions of a new genus and two new species. Journal of the Royal Society of New Zealand 30(4): 337-364. 2000
 David W. Steadman: Extinction and Biogeography of Tropical Pacific Birds. University of Chicago Press 2006