The main methodological difficulty of this study, say the authors, was that birds are hard to detect. When one samples a plot of forest it is easy to miss species that actually exist there. To distinguish real absences from detection failures, the authors used state of the art statistical methods developed by James Nichols and colleagues, at the U.S. Geological Survey's Patuxent Wildlife Research Center.
"With a handle on the detection problem it is much easier to understand real species occurrence", said Nichols, "and looking at occurrence through time, one understands the dynamics of species faced by forest destruction". Some vanish because they don't survive in a given site, others because they don't colonize new sites that become available. The two processes may also act in combination, but different species follow different ways.
The detailed treatment of the dynamics of 55 bird species allowed an unprecedented test of classical scientific hypotheses about the effects of reserve size and isolation on the local extinction and colonization of species. The species-specific estimates of effects of area and isolation on extinction and colonization processes permit prediction of effects of future fragmentation on bird communities in these Amazon landscapes.
Area is important because the forest is spatially diverse. "What might look like a vast mantle of homogeneous green is actually a multicolored mosaic", said Lovejoy. And species that occur throughout the forest at the large scale actually may have very specific requirements at the fine scale.
Large areas of forest encompass a wide enough variety of local conditions ?and species, to ensure the survival of the Amazon and its inhabitants. In December, 2006, the Brazilian government established the largest protected area ever, 15 million hectares in Northern Brazil. Sustainable conservation strategies result when
Source:Smithsonian Tropical Research Institute