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Claims that there will be a massive loss of species as tropical forests are cleared are based on the relationship between habitat area and the number of species. Few studies calibrate extinction with habitat reduction. Critics raise doubts about this calibration, noting that there has been extensive clearing of the eastern North American forest, yet only 4 of its "200 bird species have gone extinct. We analyze the distribution of bird species and the timing and extent of forest loss. The forest losses were not concurrent across the region. Based on the maximum extent of forest losses, our calculations predict fewer extinctions than the number observed. At most, there are 28 species of birds restricted to the region. Only these species would be at risk even if all the forests were cleared. Far from providing comfort to those who argue that the current rapid rate of tropical deforestation might cause fewer extinctions than often claimed, our results suggest that the losses may be worse. In contrast to eastern North America, small regions of tropical forest often hold hundreds of endemic bird species.As forests or other habitats are destroyed, the remaining habitat may be too small to hold viable populations of all the species that require it (1). Consequently, extinction follows habitat reduction. The often unmistakable destruction of habitat is vital to arguments about the global loss of species (2). With important exceptions, the species losses themselves are hard to document. We can estimate only imprecisely the total number of species an area holds. Indeed, we have names for only a tiny fraction of the planet's species (3). Our confidence in predicting species loss from habitat reduction stems from the relationship between the number of well-known species an area holds and its size. Those who point to the extensive reductions in the forests of eastern North America during the nineteenth century (4, 5) challenge this confidence. Historically, few of the region's '200 terrestrial bird species have gone extinct. Birds are well-known and we cannot plead ignorance of their extinctions. Do these observations refute the predictions of the species-area calculations (6) and so call into question fears about massive loss of species on a global scale?We review the history of deciduous and coastal plain coniferous forests in the eastern United States from European settlement to the present. Forest losses have been extensive, but they were not concurrent. In New England, for example, forests began to recover as deforestation-and many of the people who caused it-moved into the Ohio Valley. At the period of lowest forest cover, about half of the forest was gone. We also list the species of birds that became extinct and those that remain. Of the species found only in eastern North America, the species losses have been higher than we predict from forest losses. This region has surprisingly few rangerestricted bird species, however, and most species could survive elsewhere as the forests were cleared. Many tropical fore...

Dense monoculturcs of Phragmites australis (common reed) have been rapidly expanding in Connecticut's tidal wetlands at the expense of cordgrass (Spartina spp.) and cattail (Typha spp). Bird and vegetation surveys in 40 salt and brackish marshes showed that there were significantly fewer species of birds and state-listed species in Phragmites-dorninated wetlands than in short-grass marshes. Seaside Sparrow, Saltmarsh Sharp-tailed Sparrow, and Wilier, three marsh specialists adapted to nesting in short gramiholds, had low frequencies in plots dominated by Phragmites. Marsh Wren and Swamp Sparrow, however, are marsh specialists that prefer tall, reedy vegetation, and both species had signiticantly greater densities at sites with more Phragmites or cattail. Although the bird communities of cattail sites and Phragmites sites were similar, the abundance of Virginia Rails was positively correlated with percent cover of cattail but not Phragmites. The extent of pools was positively related to bird species richness in short-grass meadows but not in Phragmites plots. In Phragmites-dominated wetlands, the height and density of reed stands may inhibit bird use of any pools that are present. Muskrats create pools that may enhance bird species richness, but populations of this mammal have dwindled during the same time period that Phragmites increased in Connecticut's marshes. Although a few species may benefit from reed invasion, it has a negative impact on some marsh bird species thai have 'already declined. These findings support the continued need for marsh restoration and the control of comnlon recd.

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., et al. 2012. Positive relationships between association strength and phenotypic similarity characterize the assembly of mixed-species bird flocks worldwide. American Naturalist 180: 777-90. AuthorsHari Sridhar, Umesh Srinivasan, Robert A. Askins, Julio Cesar Canales-Delgadillo, Chao-Chieh Chen Submitted February 10, 2012; Accepted August 1, 2012; Electronically published MONTH? xx, 2012 Online enhancement: appendix. Dryad data: http://dx.doi.org/10.5061/dryad.th198.abstract: Competition theory predicts that local communities should consist of species that are more dissimilar than expected by chance. We find a strikingly different pattern in a multicontinent data set (55 presence-absence matrixes from 24 locations) on the composition of mixed-species bird flocks, which are important subunits of local bird communities the world over. By using null models and randomization tests followed by meta-analysis, we find the association strengths of species in flocks to be strongly related to similarity in body size and foraging behavior and higher for congeneric compared with noncongeneric species pairs. Given the local spatial scales of our individual analyses, differences in the habitat preferences of species are unlikely to have caused these association patterns; the patterns observed are most likely the outcome of species interactions. Extending group-living and social-information-use theory to a heterospecific context, we discuss potential behavioral mechanisms that lead to positive interactions among similar species in flocks, as well as ways in which competition costs are reduced. Our findings highlight the need to consider positive interactions along with competition when seeking to explain community assembly.

When analyzing a table of statistical results, one must first decide whether adjustment of significance levels is appropriate. If the main goal is hypothesis generation or initial screening for potential conservation problems, then it may be appropriate to use the standard comparisonwise significance level to avoid Type 2 errors (not detecting real differences or trends). If, however, the main goal is rigorous testing of a hypothesis, then an adjustment for multiple tests is needed.To control the familywise Type 1 error rate (the probability of rejecting at least one true null hypothesis), sequential modifications of the standard Bonferroni Method, such as Holm's method, will provide more statistical power than the standard Bonferroni method. Additional power may be achieved by using procedures that control the False Discovery Rate (the expected proportion of false positives among tests found to be significant). When the Holm's method and two different false discovery rate procedures (FDR and pFDR) were applied to the results of multiple regression analyses of the relationship between habitat variables and abundance for 25 species of forest birds in Japan, the pFDR procedures provided the greatest statistical power.

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