We examined how a community of insectivorous bats in upland rain forest differentially used closed canopy areas and artificial gaps produced by selective logging. Bat foraging activity was monitored at paired canopy and gap sites using ultrasonic detection equipment. The data supported the prediction that gap use was related to morphology and bat species were classifiable as closed canopy specialist, gap specialists, and gap incorporators. Closed canopy specialists were species with low aspect ratio and wing loading, whereas gap specialists had high values for these two measures. Gap incorporators, which used both canopy areas and gaps, were intermediate in morphology. The closed canopy species were presumed to forage more readily in a cluttered environment. In this community there were no strict gap specialists, but instead the gap specialists were also recorded in other, more open habitats. The community consisted of two distinct subcommunities: four species in closed canopy areas and five in gaps. Three other species were incorporators, but the incorporation rate was very low; only 8% of the activity in gaps and 27% in closed canopy areas was due to these species. There was no relation between patterns of gap use and gap vegetation cover or age up to 6 yr, suggesting that exclusion of gap specialists from a regenerating gap is a slow process. There is tight phenetic packing in the two subcommunities, indicating that vegetation structure is more important than competition in constraining the structure of this community.
Both vertebrate- and wind-dispersed seeds moved farther from rain forest into old field than from old field into forest. Vertebrate-dispersed seeds from the rain forest moved farther into the field than wind-dispersed seeds, but seeds of both types moved similar distances from field into forest.Habitat structure affected seed deposition patterns in the field, where shrubs provided perches for flying vertebrates. Vertebrate-dispersed seed deposition was significantly greater, and deposition of plumed, wind-dispersed seeds was significantly less, under shrubs than in the open. Deposition of vertebrate-dispersed seeds under fruiting shrubs was significantly less than under non-fruiting shrubs.
Seven species of fruit pigeon were studied during 3 years in the lowland tropical forest of N. Queensland to find the effect of forest species on pigeon populations and breeding habits and the basis for coexistence of 7 species. Because of the variety of plant species and the differences in their fruiting seasons, fruit was available all the year round and the diet of each species changed according to the fruit available and the selectivity of their feeding habits; none of the species studied ate anything other than fruits or seeds, the latter representing an appreciable fraction (20%) only in the brown pigeon. The foraging habits of all species were recorded and their relative abundance was assessed. Pigeons were most numerous during the dry season, which was also the breeding season. Each species selected a different range of fruiting plants owing to nomadism and migration. At any one time 2 or 3 pigeon species were common, while the rest were rare or absent. The plant family Lauraceae was of major importance. It is suggested that the many species (2250 in all) in this family have developed collaterally with the fruit-eating birds of appropriate feeding habits.
We present a novel application of Bayesian procedures to assess the impacts of logging rain forest on birds and small mammals in tropical Queensland, Australia, using data from a 1983‐1986 BACIP (measures made before and after on control and impact sites) study. The procedure was compared with the usual approach to the analysis of BACIP designs following the methods of Stewart‐Oaten et al., which are based on classical Neymann‐Pearson significance testing. Significance tests were performed at the 0.05 and 0.1 levels, power being calculated for a 25% reduction in species capture rates. For the Bayesian analysis, we elicited one noninformative and three informative prior distributions representing polarized beliefs about the effect size of logging: a strong negative effect, little or no effect, and an effect related to the amount of canopy loss. Effect size was estimated by determining the extent to which there was agreement between the posteriors for eight propositions concerning effect size. These propositions ranged from a negative effect of >25% reduction being very likely to a large positive effect of >25% increase being very likely. Of 76 bird species recorded and nine species of mammals captured, there were sufficient data for analysis of 21 bird species, five ecological groups of birds, and five mammal species. The bulk of the classical tests were of low power; of the 99 species/microhabitat combinations tested, only 10 were significant at the 0.05 level (12 at the 0.1 level). The standard classical analysis allowed few conclusions other than the data were uninformative. The Bayesian procedure was more informative. For 68 species/microhabitat combinations, there was consensus among the posterior distributions for one or more of the propositions about effect size. The Bayesian analysis indicated that, over the entire study area, negative effects were not likely to be greater than the degree of canopy opening. However, in the microhabitats that received most of the damage, negative effects were likely for far more species.
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