Stopover Ecology of Nearctic–Neotropical Landbird Migrants: Habitat Relations and Conservation Implications. Studies in Avian Biology, no. 20.— Edited by Frank R. Moore. 2000. Cooper Ornithological Society, c/o Western Foundation of Vertebrate Ornithology, 496 Calle San Pablo, Camarillo, California. iv + 133 pp. ISBN 1-891276-12-3. Paper, $18.00.—Conserving critical habitat for migratory birds is especially complex and challenging. The problems associated with habitat loss and fragmentation on the breeding and wintering grounds are apparent and have received considerable attention from researchers and managers. The stopover habitat ecology of migratory landbirds in the New World, however, is far from clear and fundamental questions must be resolved if we are to understand and conserve this important group of bird species.
In this edited volume of Studies in Avian Biology, Frank Moore and his colleagues have done an excellent job of characterizing the scope and complexity of migrant stopover ecology. This volume consists of a short introduction by Moore followed by nine papers that address an appropriately diverse set of topics on biological and political/management issues. Previously published results are summarized in several papers and new findings are also reported. I found the volume to be especially valuable in the articulate presentation of pressing questions that range from individual energetics and foraging behavior to movements of birds at the landscape and regional scale.
In the first paper, Simons, Pearson, and Moore present an interesting set of techniques and modeling protocols for spatial analysis of stopover habitat associations and movements of migrating birds. They present individual-based models depicting the behavior of migrants as they make decisions about where to land and replenish after undergoing a trans-Gulf of Mexico flight. The currencies for those decisions are the individual's condition and the intrinsic quality of a habitat patch or landscape. Those analytical techniques appear promising for developing further explanatory and predictive (simulation) models. A later paper by Moore and Aborn on the mechanisms of en route habitat selection is informative and complements the chapter by Simons et al. by summarizing the proximate mechanisms that may underlie an individual's decision to use a given habitat patch.
In another paper, Petit presents a valuable review of what is known about habitat use by passage migrants. Petit poses several basic questions about habitat selection and the types of habitats that birds appear to favor or avoid. Those patterns vary considerably among and within species according to geographic location and season (i.e. spring vs. autumn). Nonetheless, Petit offers the tentative conclusion that management strategies designed for birds during the breeding season will also be useful for en route migrants (with special provision needed for critical habitats near geographic barriers such as large bodies of water and mountains). A later chapter by Parrish on foraging plasticity (especially pertaining to switches by “insectivores” to frugivory) of en route migrants is also relevant to the issue of how breeding-season habitat can accommodate migrants. The management implications of this question are far reaching and merit critical analysis using field data and simulations.
Other papers include detailed analyses of age-dependent stopover behavior (Woodrey), a case history of stopover habitat loss along the northern Gulf Coast (Barrow et al.), and analyses of migrant use of riparian habitats in the Middle Rio Grand Valley of New Mexico (Finch and Yong). The latter paper complements the majority of those in this volume that focused on stopover ecology in eastern North America. Mabey and Watts offer a unique account of how local land-use policy can affect prospects for conserving valuable stopover habitat in Virginia's lower Delmarva Peninsula. The authors illustrate how important the cooperation of private landowners is to the conservation of stopover habitat. In the final paper, Hutto offers an insightful, sometimes personal, overview of migrant ecology and conservation. To those reading the entire volume, I recommend reading this paper first as a nice introduction to the major issues and concepts presented throughout.
The volume does not cover all issues in detail and it was not intended to be comprehensive in scope. Urban or suburban areas, exotic trees and shrubs, and new tools such as Doppler radar in the study of migrant ecology, are important topics that were not addressed in detail. Moreover, a critical analysis of the contributions of lost stopover habitat to long-term trends in abundance would have been informative. Many migratory species are decreasing over much of their range whereas others are not, and some are even increasing. Differences in the migratory behavior and stopover ecology of species that are generally increasing versus those that are decreasing would clarify the conservation importance of stopover habitat and demographic events during migration.
Notwithstanding, I recommend this volume enthusiastically to those interested in avian conservation, behavior, and life histories. The volume is an excellent introduction to the ecology of migrants, the price is right, and the compendium of references (through the mid-1990s) is useful.