A total of 114 individuals of 17 resident and 10 migrant species captured at a rainforest study site in the Tuxtla Mountains of southern Veracruz, Mexico, were displaced to a second rainforest site 2.5 km distant. Return rates to point of capture were high for both groups (73% for resident species versus 74% for migrants). These comparable rates, when considered with evidence that residents can accumulate large fat reserves, indicate that resident species possess key adaptations necessary for migratory movement.

Un total de 114 individuos pertenecientes a 17 especies residentes y 10 migradoras capturados en un enclave de selva húmeda en las montañas de Tuxtla al sur de Veracruz, México, fueron trasladados a un segundo enclave de selva humeda situado a 2.5 km de distancia. Las tasas de retorno al punto de captura fueron altas para los dos grupos (73% para las especies residentes y 74% para las migradoras). Teniendo en cuenta que los residentes pueden acumular grandes reservas de grasa, la similitud de estos resultados indica que estas especies poseen las adaptaciones necesarias para el movimiento migfatorio.

The southern portion of South America plays an important role for the conservation of many waterfowl and waders. Migratory movements were, till recently, known only for Arctic or Patagonian species. The only exception was the Southern Pochard Netta peposaca, with a west—east winter migration from the lower Parana River valley to south Brazil coastal wetlands. The banding studies that have been conducted by the Centro de Pesquisas para a Conservação das Aves Silvestres (CEMAVE/IBAMA) since 1980, directly or through agreements with local organizations, showed more details of this migration, plus indications that other aquatic species such as Chilean Flamingo Phoenicopterus chilensis, other duck species, Neotropic Cormorant Phalacrocorax olivaceus and White-faced Plegadis chihi may follow the same pattern. A migration into the same area the Pantanal population of the Wood Stork Mycteria americana was only recently discovered, and other species may also do likewise when the Pantanal is seasonally flooded. The studies of such bird migration or movements between the main South American wetlands are of great importance to understanding their conservation needs, especially when international cooperation among the countries plays a most important role. The region has been suffering human pressures of various types, from land reclamation for pasture and/or agriculture to the operation, in the last 30 years, of big hydroelectric dams which affect the natural flow of rivers or keep flood-plains under water. The impending construction of the Hidrovia Paranà/Paraguay, a large project for heavy river use as a main transportation route, may represent an enormous impact on such rich aquatic habitats, demanding immediate cooperation among the countries involved to mitigate negative effects on the environment. The impact may be similar to what happened in the Mississippi valley early this century. The west-east movements between the Paranà River valley and south Brazil are of special conservation interest, as a nationally threatened species (in Brazil) is involved (the Chilean Flamingo) as well as duck species targeted for the hunting season in the area.

Wintering Nearctic migrants constitute a high proportion of the birds present in many terrestrial habitats in the Bahamas and Greater Antilles, but their proportions decline southward through the Lesser Antilles. Many migrants winter on densely populated islands which have been extensively deforested. Current estimates show that only 21% of the land area, or approximately five million hectares, remain in forest on Caribbean and Bahamian islands, indicating that most of the major deforestation has already occurred. Although reforestation is under way on a few islands, many remnant forest fragments are threatened by humans or natural disturbances such as drought or hurricanes. Thus wintering migrants requiring closed-canopy forest are at greatest risk to habitat loss, whereas species requiring early successional habitats are not currently threatened, assuming that pesticide use does not increase. Policies which protect forests, particularly mangroves, wet limestone and montane broadleaf forests in the Greater Antilles, and broadleaf scrub (“coppice”) in the Bahamas, will be beneficial to migrants and endemic species.

Habitats at intermediate and upper elevations of the volcanic Cordillera of southwestern Guatemala harbour a diverse terrestrial vertebrate fauna that includes at least 423 avian species, 108 of which are known to be Nearctic migrants, and 43 of which are known or suspected to have both resident and long-distance migrant populations. During the course of floral and faunal inventories in a proposed Multiple Use Area in this region from 1987 through 1991, FIIT researchers collected or observed 254 avian species, of which 44 are regarded as Nearctic migrants and 26 are known or suspected to have both resident and long-distance migrant populations. Study sites included climax and selectively logged lower montane forest fragments, as well as subtropical agroecosystems. Data are presented to support the conclusion that a significantly higher percentage of resident avian species reported from this region in the literature continue to occupy these habitats than do species known to undertake cyclical longdistance migrations. Non-quantitative, historical reports of relative abundance of all Nearctic avian migrants in the region during the early and mid-twentieth century are compared with current status of these species. Threats to Nearctic avian migrants in the western Guatemalan highlands are discussed, and areas of future research for ornithologists working with this community in the region are proposed. Recommendations are made to preserve or improve habitats on wintering grounds and along migration routes considered to be of critical importance for the long-term survival of a number of threatened and vulnerable Nearctic avian migrants in Guatemala.

Although much attention has been paid to the impacts of tropical deforestation on populations of Neotropical migrants, fragmentation of breeding habitat may be an equally serious problem for many of these birds. Populations of many migrant songbirds have been declining in recent decades, especially within small woodlots. Censuses from woodlots of different sizes also consistently show that many migrant songbirds are area-sensitive, i.e. they are absent from all but the largest woodlots in a region. In contrast, long-term censuses from large, unfragmented forests show few consistent patterns of decline in Neotropical migrants. Population declines are therefore linked to forest fragmentation because they are most pronounced in small, isolated woodlots.

Over half of the 332 migratory bird species that breed in North America and winter in the tropics are affected by the obstacle to migratory flight presented by the Gulf of Mexico. Landbird migration in the vicinity of the Gulf is considered from an historical perspective, and in light of netting and observational data from the western Gulf coast. A trans-Gulf crossing from the northern Gulf coast to, or over, Yucatan is the most commonly followed fall route for eastern Nearctic migrants that winter in Central America. The spring route for these species is different, involving a more westerly trans–Gulf course for some individuals, and a circum–Gulf route for others. Prevailing wind direction and the probability of meeting turbulence over the Gulf are suggested as the main selective factors affecting route form for Gulf–area migrants.