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Tropical forest destruction and fragmentation of habitat patches may reduce population persistence at the landscape level. Given the complex nature of simultaneously evaluating the effects of these factors on biotic populations, statistical presence/absence modelling has become an important tool in conservation biology. This study uses logistic regression to evaluate the independent effects of tropical forest cover and fragmentation on bird occurrence in eastern Guatemala. Logistic regression models were constructed for 10 species with varying response to habitat alteration. Predictive variables quantified forest cover, fragmentation and their interaction at three different radii (200, 500 and 1000m scales) of 112 points where presence of target species was determined. Most species elicited a response to the 1000m scale, which was greater than most species’ reported territory size. Thus, their presence at the landscape scale is probably regulated by extra-territorial phenomena, such as dispersal. Although proportion of forest cover was the most important predictor of species’ presence, there was strong evidence of area-independent and -dependent fragmentation effects on species presence, results that contrast with other studies from northernmost latitudes. Species’ habitat breadth was positively correlated with AIC model values, indicating a better fit for species more restricted to tropical forest. Species with a narrower habitat breadth also elicited stronger negative responses to forest loss. Habitat breadth is thus a simple measure that can be directly related to species’ vulnerability to landscape modification. Model predictive accuracy was acceptable for 4 of 10 species, which were in turn those with narrower habitat breadths. [Copyright &y& Elsevier]

As natural areas are reduced into isolated remnants, the importance of secondary habitats for species conservation will increase. Consequently, the conservation value of human-modified or created secondary habitats must be determined. In this study, we evaluated the conservation potential of three habitats associated to cattle ranching (riparian forest, live fence, and pasture) for tropical forest birds in the Caribbean region of Guatemala. We studied the bird communities of five tropical forest and riparian forest (henceforth river) sites, three live fence sites and four pasture sites, in five cattle ranches in the region, and compared the four habitats based on the following parameters: species richness, number of individuals, species composition and an index of conservation importance. A 10-point series was sampled (six repetitions of each series) in each habitat site using the point-count method, in march and april of 1998 and 1999. Although forest, river and live fence had similar mean species numbers, considering all species (111, 96 and 94 species, respectively), and river and live fence surpassed the forest in mean number of individuals (80 and 72 compared to 56 individuals), river and live fence had significantly fewer mean numbers of interior-forest resident species and individuals (56, 21 and 15 species, and 61, 19 and eight individuals in forest, river and live fence, respectively). River and live fence, when compared to forest, had no significant differences in the number of resident forest-edge species and individuals, but their edge-species composition was significantly different from forest. Those resident edge species that were relatively abundant in forest had very low abundances in the modified habitats, and those that were abundant in river and live fence were rare or absent in forest sites. With respect to migratory species, both river and live fence were very important, and the river was more important than forest, according to the conservation importance index. We conclude that these modified habitats have very little value for tropical forest-dependent resident species, but are extremely important for migratory species, particularly those of arboreal habits. We also stress that the conservation importance of alternative habitats should be based on species composition, as opposed to species richness and abundance, and defined as a function of species of particular conservation importance, in our locality, those dependent of tropical lowland forest. [ABSTRACT FROM AUTHOR]

Modified-habitat use by tropical forest-dependent birds in the Caribbean region of Guatemala. As natural areas are reduced into isolated remnants, the importance of secondary habitats for species conservation will increase. Consequently, the conservation value of human-modified or created secondary habitats must be determined. In this study, we evaluated the conservation potential of three habitats associated to cattle ranching (riparian forest, live fence, and pasture) for tropical forest birds in the Caribbean region of Guatemala. We studied the bird communities of five tropical forest and riparian forest (henceforth river) sites, three live fence sites and four pasture sites, in five cattle ranches in the region, and compared the four habitats based on the following parameters: species richness, number of individuals, species composition and an index of conservation importance. A 10-point series was sampled (six repetitions of each series) in each habitat site using the point-count method, in march and april of 1998 and 1999. Although forest, river and live fence had similar mean species numbers, considering all species (111, 96 and 94 species, respectively), and river and live fence surpassed the forest in mean number of individuals (80 and 72 compared to 56 individuals), river and live fence had significantly fewer mean numbers of interior-forest resident species and individuals (56, 21 and 15 species, and 61, 19 and eight individuals in forest, river and live fence, respectively). River and live fence, when compared to forest, had no significant differences in the number of resident forest-edge species and individuals, but their edge-species composition was significantly different from forest. Those resident edge species that were relatively abundant in forest had very low abundances in the modified habitats, and those that were abundant in river and live fence were rare or absent in forest sites. With respect to migratory species, both river and live fence were very important, and the river was more important than forest, according to the conservation importance index. We conclude that these modified habitats have very little value for tropical forest-dependent resident species, but are extremely important for migratory species, particularly those of arboreal habits. We also stress that the conservation importance of alternative habitats should be based on species composition, as opposed to species richness and abundance, and defined as a function of species of particular conservation importance, in our locality, those dependent of tropical lowland forest.