9321481 Brown This dissertation research will use the North American Breeding Bird Survey (BBS) to quantify the distribution of abundance across the geographic range of a species. Two models of the distribution of abundance, differing in the position of low abundance sites, are proposed that can be tested with this data. Specific patterns either predicted in the literature or arising as corrollaries of these predictions will be tested: (1) abundance is highest toward the range center, (2) sites of highest abundance should be close together in space, (3) sites of low or zero abundance should increase in frequency near the range edge, and (4) the change in abundance from the center to edge of range will be steeper near continental than interior edges. Temporal stability of the distribution of abundance will be evaluated by examining abundance through time at sites throughout the range. Several models of the large-scale expansion and contraction of geographic ranges are proposed and tested with data from species whose distribution and abundance are known to have changed in the past 30 years. The magnitude of the effect of the environment on variance in population growth rate will be quantified and related to population size and position in the range in order to separate out these two simultaneously acting factors. %%% This research will provide a key linkage between species distribution-abundance relationships, ecology, and biogeography. The results will provide vital information regarding the abundance of declining populations of breeding birds. Such information is essential to developing a conservation strategy to help mitigate the increasing loss of bird species in North America. ***
