Ecology and conservation of large-bodied avian frugivores of Luzon, Philippines

摘要: Avian frugivores across Southeast Asia, and in the Philippines particular, are seriously threatened owing to massive loss of habitat direct exploitation through hunting pet trade. Their declines may have dire consequences for wider ecological processes as many also seed dispersers. Conservation programmes crippled by a lack knowledge on status, abundance ecology which extend other endemic species country. This PhD identified factors that influenced frugivore community composition well drivers distribution Luzon, largest island Philippines. It developed cost-effective methods gathering baseline data inform conservation measures little-known over large geographical areas. included way correcting bias caused non-random transect placement study site is often case during bird surveys tropics. Twenty-five pigeons, parrots hornbills were surveyed using distance sampling along nearly 500 km line transects at 14 sites Luzon. I documented surprisingly few reliable disappearances from individual forest patches – fact this fieldwork since 2000 has increased known extent occurrence several species. However, green racquet-tail Prioniturus luconensis suffered real range contraction. More alarming was absence most with apparently intact surveyed. Even where present, exhibited lower densities than related similar Asia. For six species, including four parrots, estimates population any reserve Luzon numbered < 1000 individuals, one-third all iii populations reserves 100. At minimum viable (MVPs) 500, communities all but 2–3 not expected remain intact. Although dispersers fare better predators (large parrots), major collapse occur serious implications ecosystem functioning. The comprise islands different origins, climate habitat, situation produce biogeographically complex set animal plant communities, themselves anthropogenic actions. explored similarities between 24 non-metric multidimensional scaling attempted explain differences terms series geographical, disturbance predictors Mantel tests. In both analyses presence/absence densities, sites/species did seem ordinate simply according region. Consistent outliers three West two Central and, rare pigeons. The strongest correlates dissimilarity altitude human measures, path width, canopy closure ‘human impact index’ (reflecting pressures management). While Luzon’s been no doubt shaped natural biogeographical processes, their effects largely obscured environmental degradation. There an urgent need understand order develop appropriate management strategies. To identify precise associations 18 avian frugivores, each 400 m long segments 213 examined relation vegetation structure composition, measured 1227 plots, generalised linear mixed models (the entered random factor). Individual showed unique patterns of iv association variables five high-altitude specialists while preferred lowland sites. Another strongly primary one thrives disturbed attendant increase food availability. then ran additive (GAMMs) non-linearities responses features. Relationships whole simple or quadratic majority suggesting there gains be had improving right gradient. Precise accurate wildlife density sizes essential evidence effective programmes. Line robust method variability detectability due line, studies cannot, necessity, based placement, instead use existing trails. hunter trails (path width 100cm) compared paths (especially cut transects). Path types altitude, differed tree girths, slope, covers, presence crops. Hunter yielded lowest encounter rates nine 12 strip seven Highest Differences trail driven rather detectability. Density calculated used should upwardly corrected average 90% (18-187%). fragmented forests always possible, correction will allow access roads adjusted. v Top list research priorities arising would map remaining populations Luzon-endemic Green Racquet-tail, Racquet-tail Flame-breasted Fruit-dove formulate intervention these threatened/near-threatened taking into account preferences threats Forest policies elsewhere tropics greatly benefit empirical described study. Sound local biologists/ecologists must encouraged further our understanding requirements, tolerance disturbance, viability populations, especially and/or SE Asia