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Birdwatching in Peru
- Birdwatching in Peru
- Flamingoes of Peru
- Villa Rica: Birding Shade Coffe
- Birds of the Amazonian River Islands
- Bamboo Birds Specialization in Southeastern Peru
Birds of the Amazonian River Islands
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 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.
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.
Birds Associated with River Island
Other specialites of the flooded forests of the Iquitos area
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