Mcgregor's travel itineraries, we know that they did not visit the higher slopes of Mt. Guitinguitin. They presumably hired local hunters to gather birds from a variety of localities and habitats. Given the broad elevational range of several of these pigeons elsewhere in the Philippines and the fact that intact forest remains on Sibuyan within this range, the disappearance of these birds cannot be explained simply by the destruction of the lowland forest. Further, there is no evidence that pigeon hunters have ever visited remote upland areas of the island. Large frugivorous pigeons in the Philippines are known to have elevational movements associated with the availability of fruits, often in large flocks and over considerable elevational ranges (Rabor, 1977; Miranda, 1987). It is conceivable that the pigeons that formerly occurred on Sibuyan depended seasonally on lowland fruit trees. The destruction of most of the lowland habitat, combined with locally intense human hunting pressure in the areas that pigeon flocks would have visited, may have led to their disappearance from he island. Cumulative records of the occurrence of Ducula poliocephala on Sibuyan may support the notion of interisland migration for this species. Mcgregor ( 1 905a) reported collecting this species on Sibuyan both in interior forest and near the sea. The only subsequent records of this vocal and sometimes conspicuous species on the island are of nine individuals taken at four different localities in late August and October 1971. The sporadic nature of these records points to erratic seasonal movements between islands. However, similar movements do not seem sufficient to explain the disappearance of the other two Ducula and the Columba pigeons from Sibuyan. The fact that early explorers found all of these species during short visits to the island and none was found after 1928, despite use of local hunters and more thorough exploration of all island habitats, indicates that these changes are real and not just a question of sampling or chance. Other species of forest-dwelling birds such as Megapodius cumingii and Tanygnathus lucionensis have serious declined on Sibuyan. Megapodius was found on Sibuyan by Bourns and Worcester (1894) and Mcgregor (1905a) but was not positively documented thereafter by other scientists visiting the island. In other areas of its range, this species often occurs in lowland and coastal forests (Delacour & Mayr, 1946; Dickinson et al, 1991), and it is often hunted or the nests robbed of eggs (Dickinson et al, 1991; SMG, pers. obs). In the 1 950s eggs of this species were seasonally available in the Magdiwang market (J. L. Tansiongco, pers. comm). In October 1991a bird hunter from Tampayan shot at least two Megapodius in the mangroves at Agnonok. Presumably, the combination of habitat change and human persecution has led to this species' rarity on the island. Tanygnathus was apparently more common at the turn of the 19th century than in recent years. An informant, about 50 years old and a resident of Jao-asan, mentioned that he had seen this species go from common to scarce within his lifetime. There are some anomalous cases of species known to occur in a variety of habitats, including those still present on Sibuyan, that were recorded by early ornithological expeditions to the island but not seen subsequently. These include Ardea purpurea, Egretta sacra, Dendrocygna arcuata, Falco peregrinus. Halcyon capensis, and Halcyon coromanda. In most cases these species were documented only once on the island, and the subsequent lack of records may be best explained by migration, rarity, or simply chance. With the conversion of much of the lowland forest through logging and agriculture, creating new habitats, a number of species that are tolerant of disturbance have colonized the island. One is Pycnonotus goiavier, which throughout its broad Southeast Asian range is regarded as "common in scrub, second growth, residential, and cultivated areas" (Dickinson et al, 1 99 1 p. 284). Until 1 954 it had not been recorded on Sibuyan. Since that period it has proliferated and is now one of the most common species in heavily disturbed areas below 75 m. Other examples include two species of open-country doves, possibly introduced to other Philippine islands by humans. Geopelia striata was first recorded on Sibuyan in 1972 and Streptopelia chinensis in 1989. Passer montanus, another species introduced into the Philippines, was first recorded on Sibuyan in 1989 at Magdiwang. In 1992 we found it in all of the large coastal villages around the island. Bubulcus ibis is first known from the island in 1972. Other recent additions to the Sibuyan list are simply the result of more intensive exploration of higher elevations (Turdus poliocephalus and Zosterops montana) and the discovery of species rare enough to have been missed or with secretive behavior (Ixobrychus sinensis, Porzana fusca, Amaurornis olivaceus, A. phoenicurus, and Cuculus fugax). In summary, the avifauna of Sibuyan has undergone some clear changes in the past 1 00 years. In several cases the recent addition of species tol-GOODMAN ET AL: BIRDS OF SIBUYAN ISLAND, PHILIPPINES 43