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Great Plains, and the southeastern portion of the 

 conterminous states generally show the greatest 

 declines, though the actual reasons for these 

 population changes will need to be examined in 

 more detail. Ceilainly, the pattern of extensive 

 declines in most of the southern coastal states is 

 quite alarming. 



Additionally, regions of the country that 

 could be particularly influenced by global cli- 

 matic change are the southern coasts (because 

 of increased stonns and degradation of coastal 

 wetlands; IPCC 1990). and the Great Plains 

 (owing to a significant decline in soil moisture; 

 Leathemian 1992). Hence, the populations of 

 birds in these areas need to be closely moni- 

 tored to ensure preservation actions are taken 

 before the combined effects of population 

 declines and climate change result in extinc- 

 tions. More studies and monitoring are warrant- 

 ed to understand the possible consequences of 

 these patterns. 



The analyses presented here can also be used 

 to investigate population trends of target species 

 across the country. Compare, for instance, the 

 trends by state for the American tree spanow 

 [Spizellii arhorea: one of the most declining 

 birds examined) and the cedar waxwing (one of 

 the most increasing birds) with maps of their 

 winter range and abundance patterns (Root 

 1988a). This comparison reveals that significani 



population trends, whether positive or negative, 

 seem to occur primarily aU)ng these species" 

 northern range boundaries and in many coastal 

 states. Such analyses could help target specific 

 regions of the country where population trends 

 of key (e.g., threatened) species need watching. 



References 



Beddall. B.C. 1963. Range expansions of the cardinal and 

 other birds in the northeastern states. Wilson Bidl. 

 7.S: 140- 1,58. 



Ehrlich. P.R.. D.S. Dohkin. and D. Whcye. 1988. The bird- 

 er's handbook. Simon and Schuster. New York. 785 pp. 



Geissler. PH.. and B.R. Noon. 1981. Estimates of avian 

 population trends from the North America Breeding Bird 

 Survey. Pages 42-.51 in C.J. Ralph and J.M. Scott, eds. 

 Estimatmg the numbers of terrestrial birds. Studies in 

 Avian Biology 6. 



IPCC. 1990. Climate change: the IPCC scientific assess- 

 ment, (also see Climate change 1992; the supplementary 

 report to the IPCC scientific assessment.) Intergovern- 

 mental Panel on Climate Change. Cambridge University 

 Press. New York. NY. 364 pp. 



Leathemian, S.P. 1992. Sea level rise: implications and 

 responses. Pages 256-263 in S.K. Majumdur. L.S. 

 Kalkstein. B. Yamal, E.W. Miller, and L.M. Rosenfeld. 

 eds. Global climate change: implications, challenges and 

 mitigation measures. Pennsylvania Academy of Science. 

 Philhpsburg. NJ. 



Root. T.L. 1988a. Atlas of wintering North American birds. 

 University of Chicago Press. IL. 312 pp. 



Root, T.L. 1988b, Environmental factors associated with 

 avian distributional boundaries. Journal of Biogeography 

 15:489-505. 



Fig. 3. Percentage of 27 birds 

 showing positive and negative 

 trends. 



For further information: 



Terry L. Root 



University of Michigan 



School of Natural Resources and 



Environment 



430 E. University 



Ann Arbor, MI 48109 



Populations of many North American land- 

 birds, including forest-inhabiting species 

 that winter in the Neotropics, seem to be declin- 

 ing (Robbins et al. 1989; Terborgh 1989). These 

 declines have been identified through 

 broad-scale, long-term survey programs that 

 identify changes in abundance of species, but 

 provide little information about causes of 

 changes in abundance or the health of specific 

 populations in different geographic locations. 



Population health is a measure of a popula- 

 tion's ability to sustain itself over time as deter- 

 mined by the balance between birth and death 



rates. Indices of population size do not always 

 provide an accurate measure of population 

 health because population size can be main- 

 tained in unhealthy populations by immigration 

 of recruits from healthy populations (Pulliam 

 1988). Poor population health across many pop- 

 ulations in a species eventually results in the 

 decline of that species. Early detection of popu- 

 lation declines allows managers to coirect prob- 

 lems before they are critical and widespread. 



Demographic data (breeding productivity 

 and adult survival) provide the kind of early 

 warning signal that allows detection of 



Breeding 

 Productivity 

 and Adult 

 Survival in 

 Nongame 

 Birds 



