This double issue of Bird Conservation International is a milestone volume in Neotropical bird migration studies that will stand independently on the shelves of many research biologists. We were very pleased to be asked, toward the end of 1993, to become the publication forum for these symposium proceedings, although this has naturally necessitated the journal taking the unusual step of publishing combined issues. There are no current plans to produce symposium volumes of this size on a regular basis, but the journal will continue to publish selected papers from BirdLife (and other important international) symposia. The journal has indeed already carried several papers presented at specialist group meetings in South America (on cracids, parrots) and several further contributions based on these meetings are expected.

Millions of birds migrate every year from breeding grounds in North America to wintering grounds in tropical America. Some 50% of the species which breed in North America spend the winter in the Neotropics. Although these migrations have been studied quite extensively, austral, altitudinal and local movements of birds are also very important but poorly documented to date.

In the course of a 13-year study of fall migration of Nearctic-breeding landbirds through a site in the Valle Central of Costa Rica, 5,549 migrant birds of 63 species, and 782 local residents of 28 species, were banded. Arrival dates of migrant species were fairly constant from year to year with passage migrants tending to arrive earlier than winter resident species. Differences in numbers and timing of first-year vs. older birds were noted in some species. Passage migrants showed higher fat deposits than did winter resident species and were virtually never recaptured in succeeding years, indicating a lack of fidelity to specific stopover sites. Winter resident species were recaptured in years following banding at frequencies approaching those for many resident species. Among winter resident species, individuals arriving early had higher fat deposits and were recaptured less frequently than those arriving later; apparently the latter were most likely to remain for the winter in or near the study area. This arrangement probably reduces intraspecific competition between transient and resident individuals of these species. Both at regional and local levels, migrant and local resident species differed in size distributions and to some extent in diet; these differences may reduce competition between these groups. Resident species had generally ceased to nest by the time the migrants arrivedin large numbers, but usually were feeding fledglings and/or moulting, suggesting that the presence of the migrants does not result in a scarcity of resources. The long-term but low-intensity, low-budget nature of this study may make it feasible to duplicate in many areas of the Neotropics, where information is needed regarding effects of land-use changes on resident and migrant avifaunas.

Austral migrants are species that breed in temperate areas of South America and migrate north, towards or into Amazonia, for the southern winter. Migrations among these species are the most extensive of Southern Hemisphere migrations, and the austral system represents a third major migration system, in the sense that the term has been applied to Northern Hemisphere temperate-tropical migration. The geography of South America greatly influences the austral system. Lack of east-west geographical barriers and the shape of the continent promote a pattern of partially overlapping breeding and wintering ranges. The suboscine family Tyrannidae, the tyrant-flycatchers, is the largest group of austral migrants, with other major families including Emberizidae, Anatidae, Furnariidae, Accipitridae and Hirundinidae. Tyrant-flycatchers constitute more than one-half of the passerine austral migrants and roughly one-third of total austral migrants, a taxonomic domination seen in no other global migration system. Parallels exist, however, between austral migration and the Nearctic and Palearctic systems. Many of the same families, including Hirundinidae, Anatidae and Charadriidae, exhibit similarly high degrees of migratory behavi-our in each system. Passerine migration in the austral system is similar in numbers to that of the Nearctic-Neotropical system, but species migrate shorter distances and breed in more open and scrubby habitats. Possible differences in year-round resource availability between South American and North American temperate forests, in addition to differing availability of these habitats, may contribute to the low numbers of forest-dwelling austral migrants.

Authors' note At the time this paper was presented at the Quito symposium, it was already accepted for publication in American Naturalist, and consequently it has not been possible to reproduce it in full here. To retain it in some form for this volume, at the request of the editors F.G.S. drafted the version below, which represents an extended Spanish summary; however, for the full text, data and complete analysis it is necessary to consult the original article (Levey and Stiles 1992).

Competition between closely related species of migratory birds is thought to be important in determining their winter distributions, habitat and resource use. However, the role of active dominance interactions has generally been downplayed. In this paper we review the occurrence of interspecific feeding territories among certain Neotropical migrants. Aggressive dominants have been reported primarily at flowering plants, but also at the honeydew from scale insect infestations, the canopy of insect-rich pioneer trees and, occasionally, fruiting trees. Although the phenomenon is uncommon, aggressively dominant species may be important in certain habitats. The presence of such interspecific territorial systems argues for the poverty of resources in the habitat as a whole. Studying aggressive interactions among migrants is a way of using bird behaviour to define critical resources for conservation management.

In this study I present data suggesting altitudinal movements of some species of foliage-gleaning insectivorous birds and related species of an oak-pine woodland of western Mexico. These movements can be regarded as short-distance or local migrations because the species involved breed in the woodlands and forests of the Sierra Madre Occidental highlands and winter in the tropical forests of the Pacific lowlands. Nine species of insectivorous birds out of 17 breed at the study site in the mountains of southern Durango and move to the lowlands in the winter; these can be regarded as short-distance or local migrants. In Mexico tropical deciduous and semi-deciduous forests are distributed mostly in the Pacific lowlands in the states of Sinaloa, Durango, Nayarit and Jalisco. Tropical forests of the Pacific lowlands are very important as wintering grounds for both North American and local west-Mexican migrants; however, there is only one protected area in western Mexico which to some degree includes these two types of tropical forests, and it is not located in the Sierra Madre Occidental, the most important mountain range in Mexico in terms of length and area covered. In addition, these tropical forests are the northern limit of the range for many tropical species. At present, these habitats are not threatened seriously by human activities (mainly forestry and cattle-raising) but this might change at any moment. At the study site the temperate highlands of southern Durango are already under the protection of “La Michilía” Biosphere Reserve, but a proposal to enlarge the area of the reserve to include the valley of the Río Mezquital and the western slope of the valley will increase the diversity of habitats, both temperate and tropical. As a consequence more bird species, as well as other taxa, will be protected in their natural environments. Such a proposal must be supported by field evidence on actual habitat use both during the breeding and wintering season, by local and long-distance migrants, in order to assess accurately the importance of this area as a representative place of western Mexico.

Frugivorous White-ruffed Manakins Corapipo leucorrhoa (Pipridae) showed pro nounced seasonal emigration from a pre-montane wet forest site (550 m) on the Atlantic slope of Costa Rica. “Resident” breeders left the area between August and October, and returned between February and April, at the onset of the breeding season. Female patterns differed from those of males primarily in later departure (October) and later return (April). I documented 57 fruit species in the diet at this locality and monitored phenology for 43 of those species, many of which were understorey members of the Melastomataceae. The emigration did not coincide with a period of local fruit shortage (relative to abundance at the same locality in other months), but the relative abundance and species composition of fruit resources in the areas to which the manakins migrated remains unknown. However, peak resources did coincide with the period in which recent fledglings would be commonest and the period during which most individuals were moulting prior ot emigration. Resources were lowest from November, when residents were absent, untilJune, well into the breeding season. Tentative evidence suggests considerable annual variation, possibly owing to differences in the timing of the rainy season. Individuals captured during the period when almost all “resident” breeders were absent (November) appeared to be transients, and were rarely recaptured. Weights differed between sexes, with females (χ = 12.5 ± 1.0) significantly heavier than males (χ = 11.1 ± 0.8). Males were lightest during the breeding season, intermediate in weight during the moulting period, and both sexes were heaviest during the migration period, when they accumulated subcutaneous fat. Females were lightest during the moult period, at which time many may also have dependent fledglings. Many other frugivores and nectarivores may engage in similar altitudinal migrations. Even where altitudinal migration is not possible, birds might migrate to other habitats with different fruit resources or phenologies. The design of nature reserves should accommodate the possibility of significant altitudinal (or cross-habitat) migration for many species of frugivores and nectarivores.

We documented habitat use by the Resplendent Quetzal Pharomacrus mocinno, a large frugivorous bird that breeds in cloud-forests in the highlands of Central America, to assess the adequacy of protection afforded to regional biodiversity by the Monteverde reserve complex, a protected natural area that includes most of the highland forests of the Tilarán mountain range in western Costa Rica. Our results demonstrated that this relatively large (20,000 ha) protected natural area does not adequately protect the area's biodiversity. Through the use of radio-telemetry, we identified the areas on the Pacific slopes that are most critical to altirudinally migrating Quetzals. These forest patches are subject to deforestation and degradation and are rapidly becoming further isolated from other remaining forest. The possibility of the local extirpation of the Quetzal, through continued habitat loss on the Pacific slopes, presents an unusual dilemma for the region because the species is the major attraction for the Ideal tourist industry which now includes over 80 businesses and annually generates over US$5 million in local revenue. Therefore, its extirpation would seriously affect regional economic stability. In order to protect the Monteverde Quetzal population, we propose a regional conservation plan that depends on participation of local landowners to protect their remaining forest fragments and allows for the development of corridors to connect critical habitats as the focus of a regional conservation effort. While the ecological significance of the structure of corridors per se, versus other possible formats, is still being debated, we have selected the corridor format primarily because it is relatively easy for landowners to grasp the concept and the necessity for continuity of the corridor network. This recognition provides an important incentive for participation across property boundaries, promoting cooperation in a group effort rather than as isolated actions. Success of this cooperative plan will provide an example for grass-roots participation in buffer-zone management strategies elsewhere in the Neotropics.

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.