NON-BREEDING SEASON CONSIDERATIONS FOR THE CONSERVATION OF MIGRATORY BIRDS IN THE MIDWEST: POST-BREEDING AND WINTERING PERIODS

--Migratory birds have the potential for population limitation on areas other than the breeding grounds. We review the state of current knowledge on the potential for limitation on wintering grounds and postbreeding habitats, with emphasis on Midwestern species and ecosystems. Although little studied, post-breeding habitat selection within the breeding grounds may be important to offspring survival, as many migrants fledge in June but do not migrate until September. We provide data on movements of wood thrush as an example of problems faced at this time. We also examine the winter ecology of Midwest migrants, including habitats used, adaptations for existence, and problems faced. In all cases, we discuss both the opportunities and constraints faced by Midwest managers concerned with migratory birds. INTRODUCTION Managment of breeding NTMBs over such a large spatial scale is difficult enough, however, Classical upland wildlife management has these migrant species also have the potential to attempted to determine ways in which mabe limited in other geographic areas. The most nipulations raise the density of local populaobvious of these is the wintering grounds; some tions of target species. The shift to managespecies spend as much as 8 months in specific ment of the diverse set of neotropical migrawintering habitat. Loss of such habitat could tory birds (NTMBs), however, requires that we lead to population declines regardless of manrecognize that populations of these species are agement activities or habitat availability on the potentially limited on scales much larger than breeding grounds (Askins et al. 1990, Sherry just local. For this reason, local management and Holmes 1995). practices may or may not result in population increases or in the preservation of target The time between fledging of young and fall species, migration has been mostly ignored. For some species in the southern part of the Midwest, a A variety of landscape or larger-scale factors single brood of young may fledge in late May or may affect distribution and reproductive early June, but parents and young do not success of NTMBs during the breeding season migrate until late August or September. In (this volume). These factors make it clear that many cases, it appears these birds leave the traits of an area being managed such as size, breeding territory and go elsewhere until shape, regional habitat distribution, and migration occurs; if special habitat needs exist, distance from population sources put strong potential limitation also could occur during this constraints on how much success a wildlife time. manager might expect for a specific area. Successful management of many migratory Habitat can also potentially limit populations of bird populations may require an understandMidwest NTMBs during migration (Ewert and ing of ecological factors extending over an area Hamas 1996). Possible limitation of Midwestof hundreds or even thousands of square breeding NTMBs during their non-breeding miles, season covers a lot of ground, both actually and figuratively. In some cases, it is possible Division of Biological Sciences, 110 Tucker Hall, that Midwestern wildlife managers might be University of Missouri, Columbia, MO 65211 able to adopt practices to aid these migrants