Rediscovery of the Pohnpei Mountain Starling (Aplonis pelzelni)
1996; Oxford University Press; Volume: 113; Issue: 1 Linguagem: Inglês
10.2307/4088951
ISSN1938-4254
Autores Tópico(s)Species Distribution and Climate Change
ResumoA specimen of the Pohnpei Mountain Starling (Aplonis peizelni) salvaged on 4 July 1995 is the first confirmed record since J. T. Marshall collected two on 7 March 1956. This species is endemic to Pohnpei, a moderately sized (about 355 kM2) heavily forested and ruggedly mountainous (about 800 m high) tropical Pacific island (MacLean et al. 1986). Pohnpei (formerly Ponape and a U.S. Trust Territory) is in the eastern Caroline Islands, Federated States of Micronesia (6?54'N, 158?14'E). In the most recent literature, A. peizelni has been reported variously as near extinction (Engbring et al. 1990), possibly (Pratt et al. 1987), and extinct (IUCN 1990). None was encountered by Pratt and his associates in 1976 and 1977 (Pratt et al. 1987) or by personnel of the United States Fish and Wildlife Service during forest-bird surveys in the summer of 1983 (Engbring et al. 1990). Likewise, none was encountered during two weeks of surveys by three teams of U.S. Fish and Wildlife Service and College of Micronesia personnel in May and June 1994 (unpubl. data). However, Engbring et al. (1990) reported on three unconfirmed sightings by three different observers during the 1970s, and many hunters and other Pohnpeians frequenting the montane forest told me they have seen A. pelzelni from time to time, but more frequently in the past than in recent years. The local (Pohnpeian) name for A. peizelni, sie (pronounced seea), is onomatopoeic for its plaintive, highpitched, sibilant whistle, which differs from the typically louder and more strident calls of its sympatric congener, the Micronesian Starling (A. opaca). Compared with the more numerous and widespread A. opaca, A. peizelni is smaller, with a proportionately thinner and less-robust bill (Fig. 1; for comparative measurements, see Baker 1951). Aplonis peizelni is also paler (gray or brownish gray) and less glossy, and it has a brown iris (yellow in adult A. opaca, but brown in young). The A. peizelni obtained on 4 July 1995 was a female with unenlarged follicles, and was shot by a local guide assisting on a herpetological survey. The guide had participated in bird surveys the previous year and knew that biologists were especially interested in finding A. peizelni. He used his deer rifle to obtain the specimen for positive identification. The bird was perched about 5 to 6 m high in an akenwel tree (Gynotroches axillaris) at about 750 m elevation in dwarf forest (i.e. moss forest or crest vegetation) about 300 m east of the U.S. Geological Survey marker on the eastern side of Nahna Laud, Madolenihmw municipality. Kotop (Clinostigma ponapensis) palms are the dominant trees, and mosses and ferns cover much of the forest floor and form dense, epiphytic layers on the trunks, limbs, and branches of other trees and shrubs. Tree ferns (Cyathea spp.), the sedge Thoracostachyum pandanophyllum, and stands of Pandanus patina also are common in the vicinity. The bird was collected at about 0800 ST as billowing clouds rolled through the forest and across the ridge. It was immediately brought to me at our camp on the shoulder of the mountain. Measurements (in millimeters) of the prepared study skin (MCZ 333054) are: exposed culmen, 18.5; bill depth at nostril, 6.1; bill width at nostril, 5.8; wing length (measured flat against rule), 100.0; tail length, 60.0; and tarsus, 26.4. The specimen was given to the College of Micronesia and, subsequently, donated to the Museum of Comparative Zoology, Harvard University. I saw no others during my two years on Pohnpei. According to Engbring et al. (1990), the species was apparently never abundant, but suffered a particularly severe decline sometime after 1930. W. F. Coultas was able to collect 60 specimens for the American Museum of Natural History in December 1930 (AMNH 331646-331705); dates on museum labels range from 1 to 21 December for 59 specimens, and 1 specimen is labelled as 26 December (P. Sweet pers. comm.). Coultas (in Engbring et al. 1990) considered A. peizelni a resident of highland and none of his records was below 425 m. L. P. Richards (in Engbring et al. 1990) recorded two at about 180 to 210 m during the late 1940s (one was collected in 1948), and he received unconfirmed reports from local residents to the effect that the species was formerly more widespread, occuring in the lowlands and also on adjacent Ant and Pakin atolls. J. T. Marshall (field notes, archived Smithsonian Division of Birds, library annex) collected a male (USNM 461509, study skin) and its presumed mate (USNM 430057, skeleton, unsexed) with one charge of shot at an elevation of about 550 m on the northern slope of Nahna Laud on 7 March 1956. His field notes mention only 5 to 10 others seen or heard while he was based on Pohnpei from August 1955 to July 1956 as a member of the Pacific Science Board's Rat Ecology Project. The reason for the decline of the Pohnpei Mountain Starling is unknown. Pohnpei has large tracts of undisturbed forest, but slash-and-burn agriculture has become increasingly more widespread, reaching to the lower limits of the dwarf forest at about 600 m elevation, and contributing stress to an already depressed population of this species. Bird hunting also is common practice among Pohnpeians, the chief game species being Micronesian Pigeons (Du-
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