-We describe a new species of sunbird, Aethopyga linaraborae, known from Mt. Mayo, Mt. Puting Bato, and Mt. Pasian, all part of an isolated range of mountains in eastern Mindanao, Philippines. It occurs commonly in mossy forest from about 1,200 m and above. We also describe a new subspecies of Apo Sunbird, Aethopyga boltoni tibolii, known from Mt. Busa and Mt. Matutum of southern Mindanao, where it is found in mossy forest above 1,000 m. Received 23 April 1996, accepted 1 August 1996. MINDANAO (97,923 km2) is the second largest of the more than 7,100 islands that comprise the Philippine Archipelago (see Fig. 1). Of the 341 species of birds that have been recorded from the island, 248 are residents, 89 are migrants or accidentals, and 4 have both resident and migrant populations. Among the residents, 20 are endemic to Mindanao and its adjacent landbridge islands of Basilan, Dinagat, and Siargao; 75 are endemic to the Philippines; and 153 are more widely distributed (duPont 1971, Dickinson et al. 1991). Dickinson et al. (1991) summarized the ornithological exploration of Mindanao that began in 1771 or 1772 when Sonnerat (1776) visited Zamboanga in western Mindanao. By the close of the 19th century, many lowland areas had been explored, yielding only five of the endemics, and a few naturalists had climbed Mindanao's highest peak, Mt. Apo (2,938 m), without obtaining any of its rich montane avifauna. However, most of Mindanao's endemic birds are mid-elevation or montane species, and with but one exception, all were discovered within this century (Table 1). In response to growing concern over deforestation and the status of the fauna of the archipelago, the National Museum of the Philippines (NMP) and Cincinnati's Museum of Natural History and Science (CMNH) initiated the Philippine Biodiversity Inventory (PBI) in 1989 to survey remaining forested areas. The PBI focused on sites that either were poorly known or never had been studied by naturalists. In 1993, the PBI team conducted surveys on three Mindanao mountains (see Fig. 1): Mt. Apo, Mt. Busa, and Mt. Puting Bato (the name used locally; on most maps it is Mt. Tagub). Among the many important discoveries of the Mindanao surveys were specimens of what appeared to be two unique populations (one from Mt. Busa in southern Mindanao and one from Mt. Puting Bato in eastern Mindanao) of the Apo Sunbird (Aethopyga boltoni), a Mindanao endemic represented by the subspecies A. b. boltoni (Mearns 1905) and A. b. malindangensis