Tropical Birding's Habitats of the World
'A Supplementary Website for Princeton's Habitats of the World: A Field Guide for Birders, Naturalists and Ecologists'
The website broadly follows the structure of the field guide, in that the habitats are arranged under the regions where they occur rather than under biome. Sometimes we had to be brutal in the book and regions such as the Caribbean are covered under the Nearctic and Antarctica is covered under the Neotropics. Because we have much more flexibility and space in the website we have split Antarctica fro the Neotropics and have also allowed for searching habitats by their biome as well as by their zoogeographic region.
Genesis of the Book
All the authors of this field guide have had a lifelong fascination with biogeography and wildlife habitats. Like the vast majority of other passionate traveling naturalists, we are most consistently interested in birds and larger mammals, while also paying some attention to reptiles, amphibians, butterflies, and other groups, especially in places where they’re conspicuous. We have all been frustrated by the approach to habitat classification used in most books and the complete absence of habitat information in many field guides. An understanding of habitats is fundamental to becoming a knowledgeable traveling naturalist, but gaining this understanding has often required slowly piecing things together yourself. What we’re hoping to do in this book is present our view of global wildlife habitats, in order to allow others to understand them far more readily than we were able to.
There are innumerable lenses through which planet Earth’s habitats can be assessed. Geology, geography, and botany are all critically important. But we don’t view any of them as the final word on habitats, and much of what these models prioritize is of little immediate relevance to traveling naturalists. A specialist in entomology or herpetology will also apply a different, and fascinating, lens to the world. A recent study of Illinois divided that US state into nearly 100 habitats based on their distinct assemblages of insects! None of these lenses is invalid, and all of them reveal fascinating things about this planet’s biogeography. Our reason for prioritizing a larger mammal and bird “lens” is that we look at the world primarily through this lens, and so do the vast majority of the world’s traveling naturalists. A handful of specialists seek out chameleons in Tanzania’s Eastern Arc Mountains, whereas millions of tourists visit the Serengeti and Masai Mara to see big mammals and glamorous birds. A few people venture to the Amazon to seek out its incredible diversity of insects, but masses visit rainforest lodges in search of monkeys, Hoatzin, and an overall “jungle” experience. So our approach in this book might lack the academic purity of a cleanly geological or botanical approach to the world’s habitats, but we think it has far greater utility to most world travelers than any other previous perspective on habitats.
In its attempt to cover the wildlife habitats of the entire globe, this is an ambitious book, in which hard decisions had to be made about what to include and exclude. We freely admit that habitats like wetlands, anthropogenic environments, and the oceans, are all worthy of far more detailed coverage. People who know their local area well may be frustrated by a lack of information about “their patch.” Please remember that this book is about giving people a broad view. It also offers a sort of “virtual travel”; the first thing all the authors do when they find out they’re headed somewhere new on the globe is conduct a bit of research about the local wildlife habitats. Deciding to “split” or “lump” some habitats was very tricky, and some of our decisions could be argued endlessly. But condensing a huge amount of research into a finite number of pages, and simply finishing this project, required a certain brutality. Our approach is certain to alienate some, but we firmly believe it will be both enjoyable and useful to other global naturalists like ourselves.
What Makes a Distinct Habitat?
We evaluate habitats based on TWO main criteria:
1) Their visual distinctiveness, which can be easily assessed by a casual observer.
2) Their assemblage of wildlife, primarily meaning larger mammals and birds, since that is our lens throughout this book. Most of the listed habitats are easily validated by a moderate score in both categories. An example is African miombo woodland, which is quite distinct in appearance from adjacent savanna habitats and supports a fairly distinctive set of wildlife, including quite a few species restricted to this habitat. But in some cases, one or the other criterion is of predominant importance. Except to the eye of a trained botanist, Indian Ocean rainforest is not very different from other humid broadleaf forests around the world. But it has almost a continent’s worth of diversity for many groups and virtually no overlap with any other place on earth. So, it is considered a distinct habitat. An example of the opposite case is African Mopane savanna. This habitat is characterized by the dominance of the Mopane tree, which is highly distinctive and easily recognizable. So the Mopane savanna qualifies strongly for the first criterion, even as it lacks a cohesive set of wildlife, having, rather, a subset of the wildlife of surrounding habitats.
The habitats are grouped into Biomes. A biome is a group of habitats with similar floral and faunal assemblages, and generally with similar climate; with most of the biomes being found in both hemispheres and all inhabited continents The term is very nebulous because habitats that are grouped into seperate biomes can actually occur as a mosaic where the habitats exist side by side or as a melange where they merge in to one another. An example of this in in coastal SE Queensland where Australasian Subtropical Rainforest (biome Humid Evergreen Forest) merges with Wet Sclerophyll Forest (Biome Australasian Sclerophyll) and Australasian Coastal Heathland (biome Mediterranean Scrub). The biomes in the fielguide are placed under ZOOGEOGRAPHIC REGIONS but on this website they can also be found under BIOMES. These are the biomes we have: DESERT; POLAR DESERT; TUNDRA; CONIFEROUS FOREST; TEMPERATE DECIDUOUS FOREST; MEDITERRANEAN SCRUB; AUSTRALASIAN SCLEROPHYLL FOREST; HUMID EVERGREEN FOREST; DRY DECIDUOUS FOREST;SAVANNA FRESHWATER HABITATS; SALINE HABITATS; and ANTHROPOGENIC HABITATS.
Likely Biomes based on their Latitude and Precipitation Levels
The graph in fig. 6 shows which habitats are most likely at any one latitude and precipitation level. What is interesting, and at first glance counterintuitive, is that habitats such as savannas and steppes cover massive areas of the planet but exist in narrow climatic bands, while other habitats such as temperate and subtropical rainforests are not very common across the planet but occur over wide ranges of precipitation. The other takeaway from the diagram is that some habitats, such as tundras, are heavily latitude- (and by inference temperature-) influenced yet can exist over a wide range of precipitation levels. Other habitats, such as Mediterranean scrub and semi-evergreen (including dry deciduous) forests, occur in a narrow precipitation range but exist over a wide range of latitudes (and again, by inference, temperatures). Across the world, precipitation of 1,200mm (48 in.) a year, or more importantly 100mm (4 in.) per month, seems to be a division between evergreen forests and those that undergo some stress due to (even short) periods of drought. This diagram does not take into account variations due to elevation (India cross-section) or continentality (Australia cross-section). Please note that the size of the habitat shown is not indicative of the actual extent of that habitat over the planet.
The book is organized by zoogeographic regions (fig. 1). These are similar to the conventional continents used by geographers and the floral kingdoms recognized by botanists but with some important differences.
There is a chapter for each zoogeographic region (except Antarctica, covered briefly in the Neotropics chapter), which contains individual accounts for all of its habitats. An alternative way to organize the book would have been by habitat category (see the Habitat Key below), but a continental approach seemed more useful, especially to travelers. The broad habitat categories, which are color-coded on the maps, and the “Habitat Affinities” section at the beginning of each account, are ways of cross-referencing similar habitats across zoogeographic regions. These are our zoogeographic regions:
Australasia is everything east and south of Sulawesi and Bali. The exact placement of this line is often debated; all the islands between Borneo and New Guinea are a transition zone in the region referred to as Wallacea (fig. 2). Deer occur on the Lesser Sundas and Sulawesi but no farther east. Monkeys reach Sulawesi, the Lesser Sundas, and a few other islands but extend no farther east.Meanwhile, marsupials are far more common in Australasia than Wallacea. The presence of eucalypts (Eucalyptus spp.) has been used as evidence that Sulawesi is part of Australasia, but paleoecology work shows that they were an insignificant part of the Australian flora until very recently, so we do not regard eucalypts as a valid indicator of what constitutes Australasia. The Lesser Sundas are included in Australasia because they have savanna and monsoon forest that are the same as habitats in Australia, with significant bird species overlap. Oceania (lands of the c. and s. Pacific Ocean including Micronesia, Melanesia, and Polynesia) is included as part of Australasia but doesn’t receive extensive coverage because wildlife distribution is determined more by each island’s remoteness rather than by the habitats it supports. Most species in Oceania tolerate a broad range of habitats.
The Neotropics runs from Central America south through all of South America. It should be noted that despite this name, much of s. South America has a nontropical climate. The limit with the Nearctic is a political one of convenience along the Guatemala-Mexico border. Antarctica is included in this section.
Indo-Malaysia region, or the Asian tropics, includes the Indian subcontinent and southeast Asia up to Sulawesi and Bali (excluding the rest of Wallacea and the Lesser Sundas). In the western and central regions, it is clearly demarcated in the Thar Desert along the India-Pakistan border and the heights of the Himalayas. In e. China, the division is messier. It is based on the transition from the predominantly tropical evergreen and semi-evergreen forests, with a monsoonal climate, to the predominately deciduous and coniferous and non-monsoonal areas of the Palearctic. This line runs, approximately, west from Shanghai along the Yangtze River.
The Afrotropics is all of Africa south of the Sahara, with a transitional area in the southwestern part of the Arabian Peninsula, which has overlap with Africa. The Sahara and the Arabian Desert effectively divide the Afrotropics from the Palearctic. Northernmost Africa has much more in common biologically with Europe than with the rest of the continent and is included in the Palearctic region.
The vast Palearctic region consists of n. Africa, Europe, most of the Middle East, and n. and c. Asia. Although there is great diversity within this region, it all shares much in common biologically and contains no clear divides. The conventional geographical divide between Europe and Asia, at the Ural Mountains, is of little biological importance.
The Nearctic includes all of North America, running to Mexico’s southern border. Biologically, this southern boundary is messy, leaving the political boundary as good as any option. But it is supported by the fact that there is only limited crossover of habitats, such as outliers lowland the Neotropics, and dry conifer forest from the Nearctic.
Common Canopy Leaf Types and Where to Find Them
The figure below depicts leaf shape, the general leaf type and the habitat where you can find them. Please note, these are general leaf shapes and do not depict all of the variations of the general leaf. For example, a Douglas fir needle will look slight different than a Black Spruce needle but in general, the look and feel is similar. These are the most common leaf types used in describing different types of forest canopy and some of the habitats where they are prominent. This does not take into account the many types of leaves of understory plants such as grasses, sedges, ferns, euphorbias, and cacti.
To help illustrate these climate variations through the year, we have created climate graphs for each habitat, based on the original work of Walter and Lieth, though we have heavily modified them to make them easier to interpret.
Reading these graphs may seem intimidating at first, but when their relevance is explained, they become more scrutable. When temperature and precipitation are plotted together, and where each 20mm (0.8 in.) of precipitation is compared to each 10 degrees Celsius (18°F), for average daily temperatures, some really interesting patterns appear. When the precipitation plot drops below the temperature plot, the area is in a time of drought, and plants are stressed because transpirationrates are higher than precipitation level. We have colored these periods in orange. When the precipitation plot is above the temperature line, the area has a surplus of water, and plant growth is strong; these periods are colored light blue. However, once the precipitation exceeds 100mm (4 in.) a month, there is an extreme surplus of water, regardless of the temperature, and most runs off and is not used by plants; we have colored these periods in dark blue. Because the whole method makes sense only when used with the metric system, we have included average daily temperature only in metric. You will also notice that measurements above 100mm er month are on a logarithmic scale, with 100mm increments above 100mm line are scaled the represented at 10mm increments below the 100mm line.
Glossary of Terms
*Although wherever possible we used non-technical English throughout this book, there is a variety of unavoidable terms, jargon, and concepts that need fuller, and often quite detailed, explanation.
Abyssal Plain: The extremely flat part of the deepest part of the ocean, not including ocean trenches
Anaerobic: Formed in an oxygen-poor, reducing environment
Aolian: Sediments derived from the wind, as opposed to water born sediments
Arkosic Sandstone: A sandstone dominated by feldspars and other minerals other than quartz.They tend to produce more fertile soils than normal sanstones. Uluru is an arkosic sandstone monolith.
Bauxite: Aluminium oxides formed in soil in warm wet/dry climates. They produce very nutrient deficient soils
Benguela Current: The cold, northward flowing ocean current along the western coast of Southern Africa that is very nutrient rich.
Benthic: Bottom of a body of water
Biome: An assemblage with similar climate, soil, wildlife and vegetation. A few local changes in these factors may allow for multiple biomes to exist in the same area.
Bioturbated: Part of the soil/regolith that has been reworked by plants or animals
Calcareous (soils): Soils from arid environments with a lot of calcium carbonate deposited within them.
Chemical weathering: The breakdown of rock through chemicl agents
Chernozems: A black, highly fetrtile soils formed beneath temperate grasslands such as steppe, prairie ir pampas.
Colluvial: Sediment transported and deposited through gravity and sheetwash rather than rivers or waterbodies.
Cryptobiotic: Inactivity due to harsh conditions
Desert: Very dry and either unvegetated or sparsely vegetated habitat.
Desertification: the degradation of more complex habitats such as savanna or grasslands to desert through human acrtivity.
Desiccation: The drying out of something
Ecotone: A transition between habitats
Enigmatic: Distinctive and different from the norm
Ephemeral: Not permentant, and often not seasonal.
Epiphytes: A non-parasitic plant that grows on another plant or surface for support.
Genera: A group of related animals ranked below family
Gleysols: A waterlogged soil with a very reducing environment
Grassland: Habitat dominated by grasses, with few shrubs or trees.
Gymnosperm: A seed-producing plants that do not produce fruit. Examples include conifers and cycads.
Hammadas: Rock outcrops and plateaus in a desert.
Halophytic. A plant that can grow in highly saline environments.
Heath/Heathland: Shrubland dominated by fine-leaved evergreen members of the erica family (Ericaceae). Highveld: The high inland plateau of Southern Africa that is dominated my grasslands
Holocene: The last “real” time period from 11,700 years to present. The Anthropocene (where humans determine the environment) has been suggested as a very recent split from this, but as of yet, the debate over when it exists or started is hotly contested and of limited value.
Inter tropical Convergence Zone: The zone around the equator where winds from the tropics and temperate regions collide. It moves with the seasons and produces the monsoons.
Karst: Caves and steep topography caused by the dissolution of rock through chemical weathering
Lateritic soil: Paleosoils and soil formed in warm wet/dry climates, where there is an intense concentration of iron and Aluminium in the upper horizon of the soils, and a pallid leached zone below where almost all elements have been removed from the soils. They are extremely nutrient deficient soils. They can be millions of years old and may bare no connection with existing climatic conditions or overlaying vegetation
Mesolithic: The later part of the stone age
Microclimate: A very localised climate that may not be related to surrounding climates, such as the base of an escarpment.Microhabitat: A localised habitat within another habitat, such as the canopy of a rainforest, or the wooed crevasse in tundra
Moorland: A moist type of heath.
Monolithic: A large uniform rock type.
Muskegs: a bog or mire in arctic landscapes
Orographic rainfall: Precipitation cause by the uplift of moist air around mountains
Oxbow Lake: A body of water cause by a river bypassing a meander, and cutting of the continual waterflow; called a billabong in Australia
Paleoshorelines: The ancient shore of a lake or sea denoted by geomorphological features such as sabd dunes
Permafrost: The ground (sediment, soil , or rock) that remains frozen hrough the tear. Generally underlies tundras or shallow wetlands
Pinnipeds: Sealions and seals.
Pisoliths: concentric nodules of aluminium and iron oxides normally formed in the upper horizons of lateritic soils.
Pleistocene: The time period (epoch) between 2.5 million years ago and 11,700 years ago. Often refered to as the Ice Age
Rainforest: Lush forest that receives abundant moisture.
Rainshadow: An area wih limited rainfall on the leeside of a mountain range which has rainfall on the windward side of the mountain
Refugia: An area where a suite of plants and animals survive during periods of unfavourable climatic conditions,
and from where they can recolonise their former distribution once favourable conditions return.
Regolith: Any material laying above fresh bedrock. Includes weathered rock, loose material, unconsolidated material and chemical deposits such as laterites and silcretes.
Sahel: The biogeographic realm in Africa seperating the Sahara and the savannas of the Afrotropics to the south. It is also regarded as an ecotopne between savanna and desert.
Savanna: A lightly wooded or treeless tropical grassland with a prominent wet and dry season.
Scree: Unconsolidated rocks on the slope of a mountain
Steppe and Prairie. Grassland in areas with a cold-winter/warm-summer climate.
Succulent: Fleshy plants with that retain water in arid climates or water deficient soil conditions
Taiga/Boreal Forest: Forest of spruce and fir trees that grows in harsh northern climates, all the way around the North Pole.
Taxa: A distinct taxanomic rank such as family, species, or subspecies.
Tundra: Open, treeless habitat of extreme environments that are covered in snow for most of the year.
Wetland: Habitat that is frequently or permanently flooded.
Xeric: A dry environment with little moisture.
Xerophytic: A plant that needs very little water and can grow in xeric conditions.
YPB (acronym): Years before present