Each year, billions of birds move between the forests of North America & tropical America. Many scientists are concerned with the decline of the magnificent migration systems as habitats are degraded on both ends of the flyways. The Smithsonian Migratory Bird Center is initiating a series of monographs addressing critical issues facing the conservation of migratory birds. Healthy populations of migratory birds depend upon the condition of habitats, which is in turn the result of good stewardship of the land. The SMBC will focus this series on land use & conservation issues that affect both migratory birds & the diversity of life in general. Most importantly, the SMBC recognizes that humans are an inseparable part of the habitat for migratory birds. The papers will present a synthetic, interdisciplinary approach to the biological conservation & social problems involved with the critical land use issues facing migratory bird conservation. The Series first contribution, FOREST PATCHES IN THE TROPICAL LANDSCAPE & THE CONSERVATION OF MIGRATORY BIRDS, will address the conservation of patches of native vegetation in the tropical landscape as a strategy for conserving migratory birds as well as an important component of sustainable land use. To order contact: Smithsonian Migratory Bird Center, National Zoological Park, Washington, D.C. 20008.
While tropical forests are being cleared at an alarming rate, the clearing is rarely complete and is often not permanent. A considerable amount of tropical forest exists as remnants that have significant value both for the conservation of biological diversity and for meeting the needs of local people. This volume brings together world-renowned scientists and conservationists to address the biological and socio-economic value of forest remnants and to examine practical efforts to conserve those remnants. An outgrowth of a year-long study by the policy program at the Smithsonian Migratory Bird Center, Forest Patches in Tropical Landscapes provides a broad overview of theory and practice, and will help foster both interdisciplinary research and more effective approaches to tropical conservation and development.
Abstract : Populations of many of Nearctic-neotropical migratory birds have declined in the past several decades, recent estimates suggested a dramatic loss of 2.5 billion birds over the past 50 years in North America. Habitat loss and degradation represent a major threat in the tropics. Managed agroecosystems have the potential to mitigate some impacts of land conversion, however, little is known regarding the habitat quality provided by working landscapes in the overwintering range. In this research, we surveyed the migratory bird community in the rapidly expanding oil palm plantations in southern Mexico; and also the declining population of the Wood Thrush (Hylocichla mustelina) inhabiting forest fragments in an agricultural matrix in Costa Rica. We assessed the value of both human-modified habitats by using a combination of demographic, distributional, and individual habitat quality indicators, as well as the relationship of these indicators with environmental characteristics. In the Mexican oil palm plantations, we found that species richness of migratory birds tended to be higher in forest patches than in oil palm, that community assemblages of migratory birds differed between habitats, and that differences in migratory bird abundance were driven by vegetative structure. Specifically, when differences in indicators occurred between oil palm and native forest, most migratory species exhibited indicators of better habitat quality in the native forest. Lastly, we observed, for the first time, territoriality in oil palm plantations and estimated home range sizes for the American Redstart (Setophaga ruticilla), which tended to be smaller than in the native forest. The Wood Thrush population in Costa Rica exhibited an average territory size estimated of 0.71 ha. We were able to determine associations between fragments' characteristics and body conditions, whereby birds in young and more humid fragments exhibited better fitness. Additionally, fragment size alone is probably not the best indicator of habitat quality for Wood Thrushes in Costa Rica. Our results suggest that most species of migratory birds assessed responded positively to forest structure complexity, and that age and sex ratios combined with measures of the physiological conditions, environmental moisture and home range sizes can be used to assess habitat quality for migratory birds overwintering in working landscapes. Importantly, determining a species' territoriality dynamics, is key when selecting a given indicator of habitat quality for each species due to distributional behavior. Our results also suggest that management strategies that promote forest-like conditions in oil palm plantations can improve the habitat quality in this agroecosystem for declining populations of migratory birds. Additionally, these findings support potential value in variable-sized forest fragments within agricultural areas for the conservation of the Wood Thrushes, and soil humidity could be used as a proximate cue for food availability and ultimately as a habitat quality indicator. Lastly, our results emphasize the importance of determining territoriality dynamics, assessing various habitat indicators, and long-term monitoring, in order to develop effective management measures to improve the conservation value of working landscapes in the Neotropics to mitigate the high rate of habitat loss and degradation, especially considering that habitat availability in the tropics could be limiting migratory bird populations.
This report was prepared in support of the National Fish and Wildlife Foundation's Neotropical Migratory Bird Conservation Program and the USDA Forest Service's role in the program. Recent analyses of data on forest-dwelling species, many of which are neotropical migrants, show population declines in many North American areas. The literature review summarizes current information on population trends of neotropical migratory birds and the factors affecting migrant populations on the breeding and wintering grounds. Opportunities for research, monitoring, and conservation of these migrants on Forest Service lands are discussed.
While tropical forests are being cleared at an alarming rate, the clearing is rarely complete and is often not permanent. A considerable amount of tropical forest exists as remnants that have significant value both for the conservation of biological diversity and for meeting the needs of local people. This volume brings together world-renowned scientists and conservationists to address the biological and socio-economic value of forest remnants and to examine practical efforts to conserve those remnants. An outgrowth of a year-long study by the policy program at the Smithsonian Migratory Bird Center, Forest Patches in Tropical Landscapes provides a broad overview of theory and practice, and will help foster both interdisciplinary research and more effective approaches to tropical conservation and development.
Agroforestry -- the practice of integrating trees and other large woody perennials on farms and throughout the agricultural landscape -- is increasingly recognized as a useful and promising strategy that diversifies production for greater social, economic, and environmental benefits. Agroforestry and BiodiversityConservation in Tropical Landscapes brings together 46 scientists and practitioners from 13 countries with decades of field experience in tropical regions to explore how agroforestry practices can help promote biodiversity conservation in human-dominated landscapes, to synthesize the current state of knowledge in the field, and to identify areas where further research is needed. Agroforestry and Biodiversity Conservation in Tropical Landscapes is the first comprehensive synthesis of the role of agroforestry systems in conserving biodiversity in tropical landscapes, and contains in-depth review chapters of most agroforestry systems, with examples from many different countries. It is a valuable source of information for scientists, researchers, professors, and students in the fields of conservation biology, resource management, tropical ecology, rural development, agroforestry, and agroecology.
Mark W. Schwartz Soon after we came into extensive meadows: and I was assured that those meadows continue for a hundred and fifty miles. being in winter drowned lands and marshes. By the dryness of the season they were now beautiful pastures, and here presented itself one of the most delightful prospects I have ever beheld; all low grounds being meadow, and without wood, and all of the high grounds being covered with trees and appearing like islands: the whole scene seemed an elysium. Capt. Thomas Morris. 1791 I am sitting in a 60-mile-an-hour bus sailing over a highway originally laid out for horse and buggy. The ribbon of concrete has been widened and widened until the field fences threaten to topple into the road cuts. In the narrow thread of sod between the shaved banks and the toppling fences grow the relics of what once was Illinois: the prairie.
The loss and fragmentation of natural habitats is one of the major issues in wildlife management and conservation. Habitat "corridors" are sometimes proposed as an important element within a conservation strategy. Examples are given of corridors both as pathways and as habitats in their own right. Includes detailed reviews of principles relevant to the design and management of corridors, their place in regional approaches to conservation planning, and recommendations for research and management.
