According to Clements & Shany (“A Guide to the Birds of Peru”, 2001), Peru supports the highest number of birds of any country, with more than 1,800 species. This extraordinary diversity is largely due to the great diversity of habitats associated with the variability of soils of distinct origins, texture, age, drainage, state of oxidation, and nutrient content, derived from the erosion of the Andes.

The area around Iquitos, in the lowland tropics of north-east Peru is especially rich in plants and animals, including birds. According

Elaenia pelzelni - Brownish Elaenia

to Dr. Haven Wiley, Professor of the University of North Carolina, who has compiled a list of birds collected, seen or recorded in and around the city of Iquitos by numerous scientists who have visited the region during the last 150 years, the area is the Mecca of avian diversity: more than 800 species, more than 1 in every 12 species found on earth, can be seen in the area. It should be remembered that this refers to a single biogeographic realm, of lowland tropical forests, between 110 and 150 m above sea-level.

The existence of such different bird communities is a due to the diversity of habitats found in the area. There are groups of birds associated with distinct types of forest and other vegetative formations, which grow on different soils and under different drainage conditions. These include terre firme forest on poor soils, amongst which those of white sand are particularly noticeable, forest on non-flooding nutrient rich soils, flooded forests on white waters or varzea, flooded forests on black water or igapó, various successional habitats associated with river islands, palm swamps, marshes, shrub-dominated swamps, bambooo-dominated forest and various others.

In a pioneering study published in 1983, J. V. Remsen and T. A. Parker (Biotropica 15(3): 223-231) showed that birds associated with habitats created by rivers represent up to 15% of the total avifauna of Amazonia. No less than 169 species (to which can be added a few more only described since that study) are associated with habitats created by rivers. A small proportion of these species (less than 5%) are also associated with secondary habitats created by man. This quantity is far greater than that associated with riverine habitats found in any other major river drainage such as the Mississippi or the Nile.

Amongst the bird communities associated with riverine habitats those associated with river islands are particularly noteworthy.

Forpus xanthopterygius - Blue winged Parrotlet

Birds and Amazonian River Islands

In the islands and transitional forests that abound along the shores of the Amazon and its main white water tributaries (especially the Ucayali, Marañón, Napo and Pastaza) it is easy to see numerous species of birds associated with these habitats that can not be found in smaller Amazonian rivers. These white water rivers are those that have their origin within the Andean mountains, in contrast to those that originate within the lowlands of the Amazonian basin. White water rivers carry high loads of nutrient rich sediments in suspension, that are deposited during periods of high water to leave islands and beaches which form the basis of one of the most productive ecosystems in South America.

The life of the Amazonian river islands is ephemeral, they are constantly being altered or eroded by the ever-changing river. They normally grow on the lower side, or the convex part of the curve, producing a succession of diverse vegetation types, and are eroded on the concave part where the current is strongest and the vegetation is most mature. The birds are therefore highly mobile, constantly moving as the vegetation develops through the successional sequence and colonising new islands as they appear.

G. H. Rosenberg (The Condor 92: 427-443, 1990) found that more than 230 birds inhabit islands in the western Amazon and its major tributaries. Of these, 19 are restricted to habitats found nearly-exclusively on islands (see table below). The rest can also be found in other riverine areas and other habitats, especially flooded forest. The author found that the densities of many of these species in island habitats reached up to 160 birds per hectare, exceeding by an order of magnitude the densities found in other wooded habitats in the Neotropics. These high densities are in part a result of the extreme microhabitat specialisation of many of these river island specialists.

The majority of these species segregate according to the structure of the island vegetation, which is in turn related to the age of the island and drainage. These factors need to be born in mind by birdwatchers, species previously observed in a certain part of an island can have disappeared in just a few months as the succession of vegetation advances, and it is necessary to constantly find new areas at the right stage of successional development in order to locate the specialities.

The table on page 38 lists the speciality species associated with river islands. The microhabitats listed for each species are those where they are most frequently found; this does not mean they cannot be seen in other habitats given the immense variability and complexity of the vegetation mosaic. Firstly the obligate river-island species as defined by Rosenberg are listed and then some of the other specialities, that whilst not being restricted to this habitat, usually also being found in transitional riverine vegetation along the shores of large white-water rivers, are rare in other localities. The numbered habitats refer to both ecosystems.

Knipolegus orenocensis - Riverside Tyrant

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Allpahuayo – Mishana was created as an officially recognized Reserved Zone on the 4 of March 1999. It is located 23 km south of

Eurypyga helias - Heinz Plengue

Iquitos. In 2004 it was classified as a National Reserve (RNAM) with an area of 58,069 ha. The reserve protects, for the first time in Peru, an area of these rare white sand forests and black water flooded forests of the Rio Nanay. The lowland rain forests around Iquitos are famous for the heterogeneity of their habitat. A combination of historical and geological events has created a mosaic of diverse soil types, from nearly pure quartz sands to red clay, in the area. Each of these soil types supports a characteristic and unique flora and fauna, and as a result Allpahuayo-Mishana supports one of the highest biodiversities of the entire Amazon basin. Many of the species are specialists of white sand forests and as such are very rare, due to the scarcity of this forest type in Peru. For example, 21 species of bird in the area are associated with white sand forests, and for several of these species, the forests near Iquitos form the only area of their distribution in Peru. At least five new species have been found and described during the last five years from the white sand forests of Allpahuayo-Mishana. The reserve is also area where two primates, the Lucifer Titi Monkey Callicebus lucifer and Equatorial Saki Monkey Pithecia aequatorialis, are officially protected in Peru.

The forests of RNAM are not only rich in unique species, they are amongst those with the highest species richness per unit area.

Topaza pyra - Fiery Topaz

Here, world records for reptiles (120 species), amphibians (83 species) and tree species per hectare (nearly 300) have been recorded. More than 1,900 plant species have been recorded in this small reserve. In the varillales more than 100 plant species are specialists to white sands. It is also supports incredible numbers of other groups: 145 mammals, 155 fish, 475 birds, including ten restricted to the Napo lowlands EBA, the majority of which are not found in any other protected area in Peru.

White Sand Forests

Forests on white sand are very scarce in the Peruvian Amazon, and have a fragmented distribution in part of the north-east (reminiscent of a chain of islands in a sea of other forest types). In Peru these white sand forests are locally known as “varillales”. The main concentration of this habitat in Peru is found in the lower Nanay drainage, near the city of Iquitos. The sand is white because it is nearly pure quartz. This type of soil contains very few nutrients, and the vegetation that occurs in these areas is highly adapted to the poor soils. In some areas there exists, below the sand, an impermeable rock layer; this causes the soil to become inundated when it rains. This further exacerbates the differences in vegetation. Several studies have shown that diverse species are restricted to these habitats, especially plants, but also some animals. Such as the 21 species of bird considered to be indicators of white sand forests in the northern Amazon of Peru.

Eurypyga helias - Heinz Plengue

Although small in extent (1 to 2 km2 on average) these ecosystems are highly unique. They have a very distinct vegetation, characterised by pronounced sclerophyllous (hard impenetrable leaves), and a highly distinctive vegetation structure (the height of the trees may be reduced, though not in all types of varillal), high levels of endemism, high tree densities, scarcity of large emergent trees, large lianas and herbaceous plants, as well as the lack of buttress roots, so commonly found in other Amazonian habitats. Additionally, many of the trees and shrubs have developed defenses against herbivores such as hard thick leaves and secondary chemicals, including alkaloids, tannins and terepenes.

Another unusual feature of these forests is that, in contrast to the majority of Amazonian forests (and tropical forests in general), they have a low diversity of species and a pronounced tendency for one or a very few species of trees to dominate.

The circulation (“recycling”) of nutrients is very efficient, and as a result the vegetation can develop a high canopy at times, in spite of the paucity of the soils. More than half the biomass of the forest is in the roots, and the water that drains from white sand forests has fewer nutrients than rainwater.

Despite their limited nature, the botanical inventories undertaken in the varillales reveal the existence of a unique vegetative community, with dozens of endemic plant species with restricted distributions. Actually, nearly 90% of the plant species fond in varillales near Iquitos are specialists of white sands, and many are endemic or only known in this region of Peru. New species for science and for Peru, restricted to these white sand soils, are discovered virtually annually.

Not just one but several types of varillal exist, in the Allpahuayo-Mishana reserve, distinguished easily by the structure of the forest and the species composition. These varying types of forest have been grouped in eight categories, based on the height of the canopy (from 1 to 30 m), the drainage of the soils (from very dry to very wet), and the floristic composition. This classification is important for conservation, given that diverse species of plants and animals appear to be restricted and exclusive to specific types of varillal.

White Sand Forest Bird Specialties by Micro-Habitat Type

Within varillales, the drainage and soil depth affect both the humidity of the forest and the height of the forest and these two factors combine to produce six types of Varillal forest (defined in the list below) with an additional Mixed Forest in marginal areas.

Conservation

Biologists have studied only a small part of the flora and fauna of Allpahuayo-Mishana, and every year new species of plant and animal are discovered. It is probable that many of the endemics of the white sand forests disappear before they are described, as thousands of hectares of this forest have been destroyed, and continue to be destroyed annually. Allpahuayo-Mishana is the only area of white sand forest that benefits from protection in Peru.

Due to its proximity to the city of Iquitos, the conservation of the reserve represents a serious problem, and conversely a great opportunity for environmental education and ecotourism. Despite the fact that the area’s status gives it permanent legal protection, this does not guarantee the actual protection of the area – due to the enormous demographic pressures that exist in the region, combined with the paucity of resources for conservation and management for protected areas in Peru.

The reserve suffers constant illegal invasions to practice unsustainable agriculture or extract timber. The white sand forests are very fragile and are in no way suitable for agriculture. Once the trees are felled the nutrients are rapidly leached from the soil, leaving an eroded and highly degraded landscape that in many cases cannot be restored.

The pressures confronting the RNAM from the neighbouring communities, promoted by high demand for natural resources by the nearby city of Iquitos, represents a latent threat to this new reserve and a challenge for its administration. At the same time the proximity to Iquitos and the easy access via the recently paved Iquitos-Nauta road, also creates a unique opportunity for tourism, recreation, education and research. The participation of the entire population, especially local communities that reside within the reserve, in the development of the RNAM is vital to ensure the long-term conservation of this unique and exceptional example of the biodiversity of Amazonian Peru.

Hemitriccus minimus - Zimmer's Tody Tyrant

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