Assessing Habitat Quality for a Migratory Songbird Wintering in Natural and Agricultural Habitats

Abstract:  As tropical forests are cleared, a greater proportion of migratory songbirds are forced to winter in agricultural and disturbed habitats, which, if poorer in quality than natural forests, could contribute to population declines. We compared demographic indicators of habitat quality for a focal species, the American Redstart ( Setophaga ruticilla ), wintering in Jamaican citrus orchards and shade coffee plantations with those in four natural habitats: mangrove, coastal scrub, coastal palm, and dry limestone forests. Demographic measures of habitat quality included density, age and sex ratio, apparent survival, and changes in body mass. Measures of habitat quality for redstarts in citrus and coffee habitats were generally intermediate between the highest (mangrove) and lowest (dry limestone) measurements from natural habitats. The decline in mean body mass over the winter period was a strong predictor of annual survival rate among habitats, and we suggest that measures of body condition coupled with survival data provide the best measures of habitat quality for nonbreeding songbirds. Density, which is far easier to estimate, was correlated with these more labor-intensive measures, particularly in the late winter when food is likely most limiting. Thus, local density may be useful as an approximation of habitat quality for wintering migrant warblers. Our findings bolster those of previous studies based on bird abundance that suggest arboreal agricultural habitats in the tropics can be useful for the conservation of generalist, insectivorous birds, including many migratory passerines such as redstarts.     

OIL AND GAS IN DEVELOPING COUNTRIES: PROSPECTS FOR AND PROBLEMS OF THEIR DEVELOPMENT

The real problem of future oil and gas supplies is not the potential physical availability of resources but the accesibility of the existing proven reserves which are concentrated in a small number of countries. Geographical diversification of reserves and production is possible with the most significant potential in the many largely unexplored and unexploited regions of the Third World. Such regions have been ignored by the oil industry either because international companies are unwelcome in many developing countries or because of the too high political risks for the large investments necessary. There is thus a geographical mismatch between oil resource potential and the human, technological and financial resources required for its development. This severe limitation on future oil and gas production is not only bad for the countries concerned but has worldwide politico-economic strategic implications in respect of pressures on OPEC and continued upward pressures on oil prices. New institutional and organizational arrangements are necessary to ensure the funding of oil and gas developments in the Third World. Le problème réel de l'approvisionnement futur en pétrole et en gaz ne réside pas dans la disponibilité potentielle des ressources mais dans l'accessibilité des réserves prouvées existantes qui se trouvent concentrées dans un petit nombre de pays. Dans plusieurs régions du Tiers Monde où l'exploration et l'exploitation ont été relativement minimes, la diversification géographique des réserves et de la production peut avoir un potentiel énorme. Ces régions ont été négligées par l'industrie pétrolière, soit parce que les compagnies pétrolières ne sont pas bien vues dans de nombreux pays en développement, soit parce que ces régions comportent de grands risques politiques vu l'ampleur des investissements requis. II y a donc un décalage géographique entre la ressource pétrolière potentielle et les ressources humaines, technologiques et financières nécessaires à son exploitation. Cette restriction sérieuse de la production de pétrole et de gaz est non seulement néfaste pour les pays en question mais a aussi des implications politico-économiques stratégiques profondes en ce qui a trait aux pressions exercées sur I'OPEP ainsi que sur la montée continue des prix. De nouveaux arrangements institutionnels et administratifs sont donc nécessaires pour assurer le financement de l'exploitation du pétrole et du gaz dans le Tiers Monde. El problema real de la oferta futura de gas y petróleo no consiste en la disponibilidad potencial de recursos sino en la accesibilidad de las reservas probadas existentes que estan concentradas en un número pequeño de países. La diversificación geográfica de las reservas y de producción es posible y el mayor potencial se encuentra en regiones inexploradas e inexplotadas del Tercer Mundo. Estas regiones fueron ignoradas por la industria del petróleo sea porque las compañías internacionales no son bienvenidas en muchos países en desarrollo o porque el riesgo político es muy alto para las inversiones necesarias. Existe pues un desequilibrio geográfico entre el potencial de recursos petroleros y los recursos humanos, tecnológicos y financieros para desarrollarlos. Las limitaciones en la producción futura de hidrocarburos es negativa no solamente para los países que sufren de ellas sino también por las implicancias política-económicas a nivel mundial con respecto a las presiones sobre la OPEP y los precios crecientes del petróleo. Es necesario establecer arreglos institucionales nuevos para asegurar el financiamiento del desarrollo de gas y petróleo en el Tercer Mundo.     

Quantifying Rarity, Losses, and Risks for Native Fishes of the Lower Colorado River Basin: Implications for Conservation Listing

Abstract:  We examined spatial distributions of fishes native to the lower basin of the Colorado River (25 species) at three scales to determine percent decline from historical distributions based on a regional biodiversity database. We cumulated records from 1843 to 1980 to develop a "historical distribution" for each species and used those occurrences recorded from 1981 to 1998 as "modern" records. We then contrasted historical and modern distributions to (1) quantify losses in spatial distribution; (2) determine how strongly these losses and fragmentation patterns corresponded to the perceived risk of extinction of each species, as represented by its status under the IUCN Red List of Endangered Species; and (3) update extinction risk rankings for 15 fishes endemic to the lower Colorado Basin according to the IUCN criteria. Based on presence and absence data, fish fauna of the lower Colorado Basin have suffered massive distributional losses. On average, ranges of extant species have diminished more than 45% relative to their historical distribution, and 35% of species have lost 50% or more of their occurrences. We provide nine new IUCN rankings and six updates to reflect more accurately the heightened imperilment of these species. Based on our new rankings, 7 of the 15 lower Colorado Basin endemics are critically endangered, 1 is endangered, 2 are vulnerable, and 1 is already extinct. We categorize the remaining 2 endemics as lower risk. This work demonstrates the utility of matching quantitative spatial metrics such as the scale-area slope statistic to extinction risk criteria for species whose persistence is strongly influenced by spatial distribution.