Introduction

Birds are useful environmental indicators. They score very highly on many of the broad criteria defined for selecting indicator taxa (Pearson 1995). Although many information gaps remain, more is known about birds than any other comparable group of organisms. They also enjoy huge popular support. For example, ca 46 million people in the United States spend time observing and identifying birds (USFWS 2003). Although birds cannot be full representatives of all biodiversity, the available evidence shows them to be an excellent starting point (BirdLife International 2004a). As an example, avian richness closely matches that of several other taxonomic groups. Indeed, with just one exception (Bolivia), all top ranking countries in terms of bird diversity are catalogued as megadiverse—a group of 17 countries that, taken together, account for at least two thirds of all biodiversity, including terrestrial, freshwater, and marine (Mittermeier et al. 1997).

The Neotropical region is a bird watcher’s paradise, with an unparalleled diversity of avian species—over 3,800 species inhabit this biogeographic region (Stotz et al. 1996; Collar et al. 1997). Seven of the twelve most bird-rich countries in the world (Colombia, Peru, Brazil, Ecuador, Venezuela, Bolivia and Mexico) lie in the Neotropics, including the four highest-ranking countries (Mittermeier et al. 1997). Furthermore, nine of the fifteen countries with the highest number of restricted-range species (with a distribution <50,000 km²) occur in the Neotropics (Peru, Colombia, Brazil, Ecuador, Venezuela, Panama, Mexico, Costa Rica and Bolivia) (Stattersfield et al. 1998). With such astonishingly rich avifauna it is not surprising birds have become a crucial element in conservation strategies across the Neotropical region.

Unfortunately, combined with this great diversity of species is a great diversity of threats, both to biodiversity in general and birds in particular. The Neotropical region includes six of the countries (Brazil, Colombia, Peru, Ecuador, Argentina and Mexico) with the most species of threatened bird in the world (Mittermeier et al. 1997; Ceballos and Márquez-Valdelamar 2000), and eight (Brazil, Colombia, Peru, Ecuador, Mexico, Venezuela, Bolivia and Argentina) with the highest numbers of threatened restricted-range species (Stattersfield et al. 1998). Over 200 globally threatened birds have already lost at least 30% of their total range in the region (BirdLife International 2004a). For instance, in Argentina ranges have significantly shrunk for 20 species owing to conversion of their habitat because of cattle ranching and drainage; in Brazil, logging, conversion to agriculture, and urban sprawl in the 15 States of the Atlantic Forest region have placed 98 species under imminent threat of extinction, with an additional 79 species regarded as near-threatened (Bencke et al. 2006). Throughout the region there are over 15 species on the brink of extinction that have lost over 99% of their former ranges (BirdLife International 2004a).

Major threats

Habitat destruction, and the associated degradation and fragmentation, are the most serious threats to biodiversity, threatening over 86% of all globally threatened bird species in the world (BirdLife International 2004a). However, over-exploitation and invasive species are also major threats, and others such as pollution and climate change are of increasing concern. In fact, for the seventeen species of Neotropical bird regarded as extinct (fifteen) or extinct in the wild (two), hunting is regarded as the primary factor in the extinction of most (ten species), with invasive species a factor in the extinction of three and habitat loss and degradation a causal factor in the extinction of seven (data from BirdLife International 2006).

Within the Neotropics, habitat loss remains the major cause of threat, affecting over 75% of all threatened birds (for 50% of these it is the only threat) (Collar et al. 1997). It has reached the point that eight regions within the Neotropics qualify as biodiversity hotspots: Madrean Pine-Oak woodlands, Mesoamerica, Caribbean Islands, Tumbes-Choco-Magdalena, Tropical Andes, Cerrado, Atlantic Forest and Chilean Winter Rainfall-Valdivian Forests (Mittermeier et al. 2004). For a region to be classified as a biodiversity hotspot it must contain at least 1,500 species of endemic vascular plants (0.5% of the world’s total), and to have lost at least 70% of its original vegetation cover (Mittermeier et al. 1999; Myers et al. 2000).

Many tropical American mountain ranges, from Mexico to Bolivia, are at risk because of habitat loss (as highlighted by three contiguous hotspots: Madrean Pine-Oak woodlands, Mesoamerica and the tropical Andes). Illegal logging has become a problem in the some areas (e.g. Pine-Oak woodlands, Mesoamerica) and conversion of natural vegetation for cash-crops or cattle ranching is pervasive in all eight Neotropical hotspots (perhaps extreme in the Cerrado, where fire is routinely used to clear the land for grazing and agriculture). The drainage and pollution of wetlands is also a significant threat, and has, for instance, resulted in the loss of as many as 14 species from the Valley of Mexico in the last hundred years (Peterson and Navarro-Sigüenza 2006). Several of the hotspots have been exploited for hundreds of years, essentially since the establishment of colonial centres in the region or even earlier (e.g. Caribbean, Mesoamerica, Atlantic Forest), and some of these now have to cope with intense demographic growth. Some areas are also under threat through a wide variety of urban developments (e.g. tourism, infrastructure), and newer threats to be added include mining (with toxic run-off) and forest conversion for lucrative drug crops that are fought by governments with wide-spectrum herbicides.

A more general threat related to habitat is climate change, which is already manifesting its effects in some areas. For example, in Costa Rica, some lowland and foothill species, like the keel-billed toucan (Ramphastos sulphuratus), have extended their ranges up mountain slopes (Pounds et al. 1999). Climate change may result in parts of the habitat becoming unsuitable for some species, which can become an important issue for species with restricted range, limited mobility, or both (Peterson et al. 2002). One of the biggest challenges regarding climate change is predicting its effects. Particular species are likely to be affected in different ways. It may alter their distribution, abundance, behaviour, phenology, morphology, and genetic composition (BirdLife International 2004a). Indirect effects, including increased pressure from competitors, predators, parasites, diseases, and disturbance, may be even more important. Climate change will probably act in combination with major threats, for example habitat loss and invasive species, and exacerbate their impacts.

Trade is another source of concern. According to WWF and the US Department of Interior, eight of the twenty-four principal wildlife-exporting countries lie in the Neotropics (Argentina, Bolivia, Brazil, Guyana, Honduras, Mexico, Paraguay and Peru), even though several of these countries prohibit wildlife exports (Bryant 2004). According to Bryant (2004), an estimated 225,000 birds are illegally imported into the US every year, most of them through the Mexican border (Cantú-Guzmán et al. 2007); WWF estimates that approximately 20,000 parrots are smuggled from Mexico every year. The pet trade has pushed several species, particularly parrots and macaws, to the edge of extinction. The Royal Society for the Protection of Birds believes the populations of several species of parrot in Nicaragua have declined by 80% in ten years as a direct result of trade, with most exports going to the European Union (RSPB 2005). It is, however, worth noting that trade nearly always occurs alongside habitat loss as the primary threats to particular species (Collar et al. 1997). Perhaps the Spix’s macaw (Cyanopsitta spixii), whose last known individual in the wild disappeared at the end of 2000, is the ultimate example of the effect that the pet-trade can have on a species (BirdLife International 2004b).

Related to trade in terms of direct exploitation is hunting, an activity that affects mostly the larger birds, and for some families, for example the Cracidae, is a significant threat to many species. The Cuban macaw (Ara tricolor) went extinct by 1885, apparently because of hunting and pet collection (BirdLife International 2004c). Similarly, for seabirds bycatch is a rapidly growing concern as these birds come into increasing contact with commercial fishing fleets. Long term monitoring studies of three species of albatross breeding at Bird Island (South Georgia)—the wandering albatross (Diomedea exulans), the grey-headed albatross (Thalassarche chrysostoma) and the black-browed albatross (T. melanophrys), indicate that all three have declined steadily since the mid 1970s, and data from other breeding sites follow similar trends (Birdlife International 2004a). Incidental mortality linked to longline fishing is the single greatest threat to albatrosses, and the albatross family is now the most threatened in the world (with 19 of 21 species globally threatened, and the remaining two near-threatened; Croxall et al. 2005). Even tropical species such as the waved albatross (Phoebastria irrorata), previously thought not to be threatened by fisheries, have been shown to be affected by bycatch (Awkerman et al. 2006).

Invasive species are a cause of concern that is particularly acute for island systems. Rats, mongooses, domestic cats, and dogs have affected some Caribbean islands, primarily through predation, whereas goats, pigs, and sheep have put pressure on some of the Pacific islands (e.g. Socorro Island, Martínez-Gómez et al. 2001; and the Galapagos Islands, Cruz et al. 2005), because of severe degradation of the habitat (Stattersfield et al. 1998). Globally, nearly 30% of all threatened bird species are affected by invasive species (BirdLife International 2004a), and many are subject to multiple effects from a variety of invasive species (a combination of both habitat degradation and predation).

Bad as this may seem, it could be merely the tip of the iceberg. Compared with other taxonomic groups, birds are doing relatively well in the Neotropics. Although approximately 10% of Neotropical bird species are regarded as globally threatened by the World Conservation Union (IUCN), there are at least 16% mammals in the same situation. These data are based on the last mammal assessment; ongoing global assessment will probably reveal the proportion is higher. Almost 40% of amphibians are also included in this category. Two out of every five amphibian species are thus threatened-it is likely that as many as 117 species of frog have become extinct in the Neotropics, and most of these (109) after 1980 (Young et al. 2004). The situation in other less surveyed groups, for example fresh water fish or orchids, may be also less rosy than for birds. With such a situation unfolding before our very eyes it is, then, necessary to be strategic in our approach to conservation

Important areas for conservation

Both BirdLife International and Conservation International have developed a strategy focussed on identification of areas of importance for conservation: the important bird areas (IBAs) and the key biodiversity areas (KBAs). These are areas that hold unique biodiversity that must be conserved immediately. The IBAs can be thought of as the avian component of the KBAs, which are defined on the basis of information for as many species as possible from the entire taxonomic spectrum. This multitaxa approach for site prioritization has been applied to complex biota, for example Mexico (Arriaga et al. 2000) and Brazil (Instituto Socioambiental et al. 1999; Veríssimo et al. 2002) where several characteristics, for example area extension, ecosystem diversity, vegetation types and coverage, soil types, presence of endemic or endangered taxa, and species richness, among others, are evaluated. Other initiatives have also taken this approach focussed on a specific taxonomic group, for example the important plant areas (Anderson 2002), prime butterfly areas (van Swaay and Warren 2003), and others. What these strategies have in common is that they identify sites of global importance for biodiversity conservation. These sites are identified using site-occurrence data for species of conservation significance, following two important considerations: vulnerability and irreplaceability (Eken et al. 2004).

Vulnerability refers to temporal options to preserve a given set of species—those areas whose needs require immediate attention, because if we wait there will be nothing to preserve. Vulnerability is based on a single criterion—the presence of globally threatened species, reflected in the categories used by IUCN (CR, EN, VU). The IBAs and KBAs are thus sites in which one or more globally threatened species regularly occur in significant numbers.

Irreplaceability refers to spatial options to preserve a given set of species, and is based on three different criteria: presence of restricted range species, congregatory species, and biome-restricted assemblages. BirdLife has used an absolute threshold of 50,000 km2 to define restricted-range species (Stattersfield et al. 1998). This has been suggested as a robust rule of thumb across taxa, although this figure is somewhat flexible; for example, a larger figure (75,000 km2) is being used to define restricted-range mammals (Schipper, personal communication) whereas it could be argued that a smaller range could be more appropriate for amphibians. Also considered irreplaceable are those sites that hold large proportions of the global population of a species at any given time. This criterion thus considers sites hosting breeding colonies, important foraging spots, or migration stopover places. Following the threshold established by the Ramsar Convention, 1% of the global population of a species is usually set as the trigger for this criterion. The third criterion, biome-restricted assemblages, is the less well developed. It addresses the fact that, given the heterogeneity of the planet, there are assemblages of species that are unique to a given environment and are thus an element of biodiversity that requires our attention. These sites must hold a significant proportion of the group of species endemic to the biome under consideration.

Birdlife is at the forefront with the definition of IBAs. More than 8,500 sites of global significance have been defined for over 160 countries using the same standard criteria. For the Neotropical region, BirdLife has identified nearly 2,000 sites in 30 countries (http://www.birdlife.org), with the Caribbean and Central American IBAs as their most recent addition, e.g. Mexico (Arizmendi and Márquez-Valdelamar 2000), Tropical Andes (Boyla and Estrada 2005), and Argentina (Di Giacomo 2005). These sites have, moreover, not only been identified as points in a map but actual polygons have been defined using species-presence information, and complemented also with vegetation maps and altitudinal information that help BirdLife set meaningful borders for each identified IBA; this has been a great effort of some non-governmental organisations (NGOs) in the different countries (e.g. ProAves, Colombia; Fundación Jotococo, Ecuador; and Armonia, Bolivia). This avian information is often used as a first approximation for the KBA definition, supplemented with information relevant to as many non-avian taxa as possible. It is important to mention that identification and refinement of important areas for conservation is an iterative exercise that is improved as more varied information and better quality data are added to the process.

There is an important subset of areas for conservation that deserves special attention—areas known to hold the last remaining populations of critically endangered or endangered species. Based on the criteria already mentioned, they would be regarded as being of extremely high irreplaceability—the species is restricted to a single site, and if the site is not safeguarded the species is lost—and extremely high vulnerability—the species in question is listed as critically endangered or endangered. These are sites that require immediate action to prevent extinction, and are the most urgent site-scale priorities (Ricketts et al 2005). The Alliance for Zero Extinctions (AZE; http://www.zeroextinction.org) has been set up to identify and safeguard these sites, and is supported by over 60 international, regional, national, and local NGOs. Globally the AZE has so far identified 595 such sites that must be protected to avoid the extinction of 794 species (217 or which are birds)—because identification so far has been restricted to data from mammals, birds, amphibians, some reptiles, and conifers, it is expected that these figures will increase as data from other taxa are incorporated into the analysis. Although many AZE sites are not triggered by birds, many still qualify as IBAs. Globally, 26% of all non-bird triggered AZE sites have also been identified as IBAs, and this figure will doubtless increase as more IBA inventories are completed. Six of the top ten countries with most AZE sites occur in the Neotropics (Mexico, Colombia, Brazil, Peru, Ecuador, Cuba), including the top four places worldwide, and six sites with five or more trigger species. Three-hundred and thirteen AZE sites have been identified in the Neotropics for 416 species—94 avian trigger species in 78 AZEs. Of these, only approximately 40% of the sites are known to have any statutory protection.

Capacity building and research

Bleak as the picture may seem, there are also positive signs in this region. Avian research seems to have taken off in the Neotropics, and recent years have seen a new generation of Neotropical ornithologists trained in the best universities and research centres worldwide. For example, between 1996 and 2005 the number of scientific articles dealing with the Neotropics in The Auk, a leading ornithological journal, increased fourfold (Fig. 1). There is a British journal (Cotinga) devoted solely to Neotropical avifauna, the number of local ornithological journals has grown (many of these have benefited from internet formats—e.g. Revista de Ornitología Colombiana, Revista Huitzil, El Hornero, Revista Brasileira de Ornitologia, Poeyana, among others), and the regional journal, Ornitologia Neotropical, is now listed by the Institute for Scientific Information. General journals (e.g. Biotropica, Oecologia, Biodiversity and Distributions) are another source of information; these now publish much information on Neotropical birds. There has also been a substantial increase in the number of local books dealing with the conservation of avifauna of the region, for example Colombia (Renjifo et al. 2002), Venezuela (Rodríguez y Rojas-Suárez 2003), Ecuador (Granizo 2002), México (Gómez de Silva and Oliveras de Ita 2003), among others, and others are in preparation (e.g. Cuba; A. Kirkconnell, personal communication), This summer Brazil announced its first Graduate Program (M.Sc. and Ph.D.) in Tropical Biology (J. Silva personal communication), which will be added to the great quantity of programs that already exists in some universities in Latin America, for example in Mexico (graduate programs in Biological Sciences), Costa Rica (graduate program in Conservation of Biological Resources), Venezuela (Ph.D. programs in Ecology, Zoology and Botany), Colombia (graduate program in Forests and Environmental Conservation), and Chile (M.Sc program in Wild Areas and Nature Conservancy). There is also evidence of more institutional collaboration between the Neotropical and other countries. For example, some American and Canadian institutions are helping to build monitoring capacity. Birds are well known relative to other taxonomic groups; they have much appeal with the general public, and are thus a good starting point for monitoring the state of the environment in these selected important areas for conservation.

Fig. 1
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Number of articles dealing with Neotropical issues published in The Auk between 1996 and 2006

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Perhaps most importantly, the community of Latin American ornithologists and birdwatchers is growing. The Colombian birdwatchers network now has 400 members and Aves Argentinas (an Argentina bird-conservation organization) has 1,000 members. Although such numbers are low by Western European and North American standards, they are important indicators in countries where there is little or no tradition of membership of conservation organizations. Increasingly, this community is becoming focussed on conservation issues (e.g. the 400 members of the Incaspiza discussion group about threatened birds in Peru) and is seeking training (e.g. an average of 205 graduates from the Argentina Naturalists’ school between 2000 and 2005). Conservation organizations have also had some success in using this community for assistance with research and monitoring. During 2000–2004, 502 volunteers participated in the Neotropical Waterbird Census organized by Wetlands International, conducting censuses at 335 sites in nine countries in South America (López-Lanús and Blanco 2005). The ornithological community must now ensure these gains in capacity and knowledge are converted into action that help us preserve the biodiversity of which we are part.