Neotropical Birdwatching | Some neotropical ornithology

Some neotropical ornithology

We don’t want to scare you off, but we thought it might be helpful to introduce the out-and-out birdwatcher in you to a little neotropical ornithology.

Topics like avian biogeography and centres of endemism may or may not have been attractive to you until now, but you will certainly find them helpful as you get to know the neotropics.

Neotropical profusion

To start from square one, the neotropics, for biologists and ornithologists (and so for birders), is the whole of Latin America and the Caribbean from the southern states of the USA south to the Antarctic peninsula, not just the part that lies in the tropics. It is one of the five bio-geographical realms into which the world can be divided according to where different sets of species tend to be found.

For birders, the neotropics is by far the best of the lot, with over 3,600 species to be found on the mainland, and more than twice as many endemic bird families as any of the other realms.

There are two basic reasons for the neotropics’ dramatic supremacy amongst the world’s populations of birds. First, the neotropics spans a wide spectrum of habitats, many of which are more or less unique to this part of the planet. Secondly, species densities are much higher in the tropics than in temperate regions—an area of tropical forest holds roughly ten times as many species as its temperate forest equivalent—and the neotropics includes a large proportion of the world’s fertile tropical land area.

For the newcomer to neotropical birdwatching this variety of birds, while exciting, can be daunting too. On a first visit to a rain forest lodge there may be 580 species to see, including 40-60 species of antbird or 100 species of flycatcher. New species are being discovered each year and taxonomies of known birds are being rapidly revised with new DNA studies.

Fortunately, help is at hand. A new understanding of neotropical birdlife is emerging that makes bird-watching in the neotropics an increasingly accessible and rich experience.

Where the birds are—habitats and endemicity

Thanks to a growing body of work by neotropical ornithologists and conservationists, there are some simple ideas to help us understand where the birds we want to see are most likely to be found. Avian biogeography is a developing area of ornithology which will undoubtedly become ever more useful, but even now it can already help amateur birdwatchers understand what birds they are seeing and where they should go to see more of the same, or others which are different.

In short, which species are found where is partly determined by habitat, and partly by history.

Habitats

Clearly, it is the present-day environment of a place that allows a species to survive and flourish there now.

The Andes is by far the most important feature determining habitat in South America. Dividing the continent from north to south it provides continuous corridors of cloud forest on the east and west slopes and a tremendous range of upland habitats from deserts and semi-arid scrub to high polylepis woodlands and alpine grasslands. The diversity of birds living in the Andes alone far exceeds that of Europe or the USA.

Lowland habitats cover great swathes of the continent. The biggest is the lowland rain forest of Amazonia, larger than Western Europe and regarded as the most diverse terrestrial habitat for birdlife. There are two more: the Chocoan rain forests west of the Andes and the Atlantic rain forests of Brazil which also provide similarly complex ecosytems for birds and wildlife.

The other lowland environments are also very interesting. South of Amazonia, the Caatinga and Chaco regions are semi-arid thorn scrub and deciduous woodlands, each with a rich endemic fauna. More open habitats range from the Atacama desert and Patagonian grasslands to the scrubby savannas of the Cerrado region of Central Brazil. The wetlands and marshes are equally impressive and deserving of a birder’s attention. The Brazilian Panatanal and Venezuelan Llanos are the best known of these, each supporting spectacular bird and animal life, but the Llanos de Moxos in Bolivia and the Ibera marshes of Argentina are no less impressive and on a vast scale. The temperate grasslands of the south—the Argentinian pampas and Patagonian steppe—support some wonderful but progressively less diverse bird populations.

Technically, present-day habitat is described most broadly in terms of biomes. One such biome is ‘tropical and subtropical moist broadleaf forest’—the lowland rain forest that covers most of Amazonia for example.

Biomes are very major classifications that are often too broad to be much use in describing a bird’s distribution, particularly in heavily speciated environments. There have been several attempts to define smaller regions of habitat that can be described with more precision. The most helpful so far is the division of biomes into ecoregions. For example, there are 181 ecoregions of lowland rain forest in the neotropics, and detailed descriptions are available for each one. This level of specificity is much more useful when describing the habitat where bird species are to be found. They express rather precisely the characteristics of climate, terrain, vegetation and other life that typify an area and thus constitute the living conditions available in a particular place for the birds of today.

There are limits to this of course, which is where the practical field skills of the accomplished neotropical birder come to the fore. Within most habitat types there is an array of ecotones and microhabitats. In an area of lowland rain forest, for example, there might be floodplain and terra firme forest, white sand woodlands, river islands and bamboo patches. Each has its own set of species. As your birding skills grow you will learn which species to look for in different parts of the forest, even along different parts of a short forest trail.

In the neotropics there can be considerable specialisation and thence speciation even within a particular microhabitat. In lowland rain forest again there are birds that specialise in turning over dead leaves to find insects to eat, and others that are adapted to looking for their dinners on the underside of live leaves a few feet off the ground. There are also species that look for insects in the higher branches. All this creates a vertical division of the same microhabitat with each stratum favoured by different birds, so if you hear the call of a particular antwren you know you should be looking for it about 8 or 12 feet off the ground.

Foraging techniques are important ways that birds specialise. The antbirds are a prime example. Antbirds don’t eat ants, they follow army ant swarms across the forest floor picking up insects as they flee the voracious horde. They work in mixed flocks of different species, each taking on different roles. Some will be the look-outs, making warning calls when danger threatens, and drawing their wages with an occasional false alarm to steal a juicy insect when the others fly up.

Similar mixed flocks work in cloud forests, though here there are no sentinels. Cloud forest life is a high energy business so the bright tanagers and others in these flocks are constantly on the move and present a colourful and exhilarating challenge to birders.

It’s a wonderful tapestry of life, that in the neotropics is very finely woven. Exciting scientific discoveries are being made that enliven and enrich the daily experiences of the practical birdwatcher out in the field.

Endemicity

We saw that maps of biomes and ecoregions help us understand what habitats are available for birds today in a particular area. The current habitat is only part of the story, however. It is past history that has determined which species have, through accidents and evolution, established populations in a particular place.

Some species flourish more or less wherever their preferred habitat occurs and can be found scattered widely—the two Kiskadees, Little Blue Heron, and Black Vulture are examples. These are robust birds that can thrive in many situations and that move around a lot from place to place. More often than not, however, bird families have speciated differently in different regions of the same biome, and often within the same region. Evolution appears to work so freely in the neotropics that it only seems to take a minor preference and a slight reluctance to stray far, albeit sustained over a long period, for a new species to be created.

Fortunately for birdwatchers, ornithologists have found that different species occur within similar boundaries across several families, and they can thus identify common areas of endemicity in which this species of toucan and that manakin will be found, but never their close cousins. Each is an ‘endemic bird area’ (EBA for short) and is home to its own individual suite of species that are not found elsewhere.

So, you will tend to find, very broadly, the same birds in similar conditions anywhere in the same EBA, but many differences between the birds in different EBAs—even where the habitat is broadly identical.

There are 5 major EBAs within the biome that covers the Amazon, for example. They have their origins in different islands of forest that remained while changes in climate tipped the balance more in favour of grassland, and which were then kept separate for long enough for avian evolution to take a different course in each. Their boundaries are often along ancient rivers which acted as barriers when the forests recombined.

The distribution of some birds amounts to just a dot or two on the map. Reduced in scope most often by loss of habitat, or perhaps by natural isolation or competition from other species, they cling on to existence in tiny populations. Being a birdwatcher you’ll want to see them if you can, and also contribute to their conservation wherever that’s possible.

Planning your birding

This is where the practical birder in you can start to get excited. You already know that to see a lot of birds you have to visit a lot of habitats. Now you also know (if you didn’t before) that you need to visit different EBAs too.

For example, although there are just 3 significant regions of lowland rain forest (Choco, Amazon and Brazilian Atlantic) in South America, there are 7 different suites of neotropical lowland rain forest birds, because of the Amazon’s 5 areas of endemicity. To see all the lowland toucans and aracaris, or all the lowland forest manakins, you would need to visit them all.

It makes sense to plan your birding trips accordingly. Broadly speaking, you would visit the EBAs of different habitat types if you seek variety, but EBAs of the same habitat type if you prefer to specialise. Only a dedicated specialist would choose to explore different parts of the same EBA, such as the mountains of southern Colombia and those of Northern Peru (both are within the ‘North Andean’ EBA), unless in search of very range-restricted birds.