Bird Diversity in the Machu Picchu Historical Sanctuary

The South American continent holds almost one third of all bird species found on earth, as well as a wide variety of bird families and endemic species. Peru is one of the South American countries with the largest numbers of species, thanks to the great diversity of habitats found here, with over 1850 species being recorded. This great diversity is reflected in the Machu Picchu Historical Sanctuary, where in an area of only 32,590 hectares, to date 423 species of birds have been recorded and a further 40 or so species may well be expected to occur as research continues.

Machu Picchu is on the eastern slope of the Andes, where humid montane and pre-montane forest drops away towards the Amazon Basin. The lowland Amazonian forest at the base of the Andes holds the highest count of bird species that can be found in one place however, the slopes of the Andes are richer in species turnover over a more extensive area. 1000 bird species can be found along a 200 km transect from the high Andean grasslands down the eastern slope of the Andes to the Amazon lowlands. This is about the same number of species that can be found throughout the whole of the Amazon basin.

As one ascends or descends the mountainous Andes, the most important variable factor affecting plant life and consequently the avifauna, is the change in temperature, which is about 0.6 degrees Celsius per 100 meter altitude change. Weather systems in the southern hemisphere move from east to west across the Amazon rainforest, picking up moisture from the humid environment as they go. On reaching the Andes the humid air rises and is cooled and the terrain becomes blanketed in clouds and mist for much of the time. This is why a popular term for the moist eastern slopes is cloud forest. Even during the distinct dry season from May to September, the cloud forest interior above 2000 meters remains cool and moist. High in the Andes above 4000 meters the situation is very different with intense solar radiation by day and biting frost at night.

The forest structure on the east slope of the Andes gradually changes from the lowlands to the Andes. At 2000 meters trees are 20-30 meters tall as can be seen in the Mandor Valley close to Machu Picchu. Trunks are often straight and smooth and Cecropias, fast growing pioneer trees with large silvery leaves, are a common feature. Above this altitude, the forest becomes lower and impenetrable with gnarled, often twisted trunks, with abundant epiphytes – moss, lichen, ferns, orchids and bromeliads. Even higher at around 3200 meters the upper cloud forest (also known as elfin forest) is even more stunted and draped in lichens and moss with dense, small leathery leaved trees. These shiny leaves condense moisture into droplets that form the characteristic mist in these areas and are an important source of moisture in the dry season from May to September. Even higher, above 3800 meters, forest fragments and patches consist of mainly one kind of tree known as Polylepis, characterized by small shiny leaves and a papery, peeling red bark. These woodlands are under intense pressure due to overgrazing and thus the lack of forest re-generation, burning and the cutting of trees for firewood. The birds found in these forest fragments are not very conspicuous but are some of the most endangered species on Earth and it is important that some of these woodlands are within the Machu Picchu Historical Sanctuary, as very few conservation units in South America protect this type of habitat. Even higher in humid parts the habitat is known as paramo, consisting of spongy vegetation of small bushes, tall grass and mosses. In drier areas this is replaced by a uniform covering of bunchgrass known as puna. Above 4400 meters the vegetation becomes very sparse, mainly rosettes and cushion plants that can tolerate the intense solar radiation from the sun, frost and snow. Glaciers start at 5000 meters and are noticeably retreating.

Machu Picchu and nearby areas are well known for the high incidence of endemism and near endemic species of birds, plants and other organisms. An endemic species is species that exists nowhere else. This is probably due to the unique topography of the area. Most of the Andean slope inclines more or less directly towards the Amazon lowlands, but at Machu Picchu the area between the Mapacho and Apurimac rivers forms a large fan of projecting mountain ridges separated by deep valleys. Machu Picchu is perched above the Urumbamba river which separates the Cordillera Vilcanota from the Cordillera Vilcabamba. In both mountain ranges, peaks reach to around 5,700 and 6,000 meters. Meteorological satellite analysis shows that these high mountain ridges provide very good protection from cold southern wind movements, known as “friajes”, that are a characteristic of the southern winter between May and September. These southern winds, characterized by short cold spells plus snow and hail on the Andean slopes, may have been influential in the development of vegetational change in the glacial eras. Throughout the tropical Andes, the highest concentration of endemic birds are to be found in areas of ecological stability, suggesting that endemic species represent relict populations which could survive periods of climatic instability only in places that were protected against extreme weather variations. In areas like Machu Picchu, survival of these relict species played an important role in the development and evolution of Andean avifauna.

It is no coincidence that areas with a high count of endemic birds and a great diversity are often close to densely populated areas and centers of past high cultures such as the Incas. The special environmental conditions and benign climates which protected relict bird species may also have facilitated the development of human populations in the Andes. Crop predictability may have been a major prerequisite for the transition from hunter-gatherer to sedentary farming communities and advances in agricultural technology. The pattern of human settlement is also affected by the development of fertile soil for farming on the transition zone between humid and rain-shadow areas where there is a balance between soil leeching and evaporation. Machu Picchu is at the juncture of the humid low Urubamba basin and the benign Vilcanota valley that was the center and ‘breadbasket’ of the Inca culture. It is also no coincidence that some of the rarest Andean birds are found in forest fragments that surround the more isolated Inca ruins and terraces of the Machu Picchu area. One of the major challenges for conservation biologists will be how to conserve bio-diversity in areas close to dense rural populations.

Much of the Andean Cloud Forest zone is steep and inaccessible and consequently not well populated except in ribbons along major road networks. The forest is often modified by natural criteria such as small and large landslides, which in turn give rise a successional vegetation growth of bushes and bamboo. The high rainfall and consequent landslides help maintain a mosaic of micro-habitats and biological diversity. Cloud forest is not suited to agriculture – it is extremely wet, steep and cool and its shallow top soil is easily washed away into rivers and streams once the soil is exposed to the elements by man made deforestation. Fields can normally be cultivated for a few years only before being left fallow for several years in order to regenerate. Small scale habitat disturbance by a low rural population is not much different in effect from natural landslides, but new roads facilitate colonization and large areas can be cleared and turned into fields and low bushy shrubbery. This can be seen below the Machu Picchu Sanctuary in the Urubamba valley but fortunately is not an influence at Machu Picchu. Habitat disturbance is a long term ongoing process and the most drastic changes seem to have taken place thousands of years ago in the highlands and montane basins. Examination of plant remains in lake sediments near Ollantaytambo close to Machu Picchu suggest that the area was totally deforested and degraded some 1000 to 4000 years ago (Chepstow-Lusty et al 1998). Much later agro-forestry systems were introduced by the Incas and the area was brought into sustainable footing again until these land management systems were interrupted and by the Spanish conquest of Peru. Today much of the Cusco area is severely degraded. Highlands are routinely burned to stop encroachment by forest to provide pasture for sheep and cattle. Much burning occurs for no apparent reason in August and September, perhaps in the belief that the smoke causes cloud build up and the onset of the much needed rains. At this point in time tree-line is located several hundred meters below its natural position and the original transitional habitat of bushy forest has almost totally disappeared and exists in very few places such as isolated northern Vilcabamba 70-100 kilometers northwest of Machu Picchu. Perhaps only 1% of Polylepis forest remains and this is fragmented into isolated patches where some of the rarest birds on earth still survive. Some patches occur in the Machu Picchu Historical Sanctuary and should be given priority protection. Until only a few years ago porters attending tour groups hiking the Inca trail routinely used Polylepis and other trees and shrubs to cook food and keep warm.

Biodiversity and its conservation are often in conflict with poverty-driven pressures on the natural environment and national strategies by government entities. Reaching the balance between land development and conservation is essential but a difficult objective to achieve in countries such as Peru where socio-economic problems take priority over conservation and public funding for environmental issues is limited. The ignorance of local inhabitants is also a factor. Protecting biodiversity can be achieved by creating a network of reserves or by better land use. In both cases education is an essential ingredient. The eastern foothills and slopes of the tropical Andes are the richest areas in the world for avian diversity and the Cusco area and northern Bolivia area amongst the most rich. Threatened species of birds are more locally aggregated in the Andes with concentrations in the Maranon and Tumbezian areas of northern Peru and also in the Cusco/Machu Picchu region. It has been traditional to rank conservation priorities by the total number of species in a given area, but this is not necessarily the best method of reducing extinction rates. If we were to decide to protect the 50 most species rich areas in South America, these areas would contain about 77% of all bird species, but many species would occur in all areas, whereas only 40% of threatened species would occur anywhere in the 50 areas. Studies using the WORLD MAP computer software developed at the Natural History Museum of London have shown that a minimum set of 28, 15 degree areas are needed to protect all Peruvian birds. Machu Picchu contains six species of threatened birds that are not covered in any other of the 28 target areas – Royal Cinclodes Cinclodes aricomae, Whiate-browed Tit-Spinetail Leptasthenura xenothorax, Junin Canastero Asthenes virgata, Inca Wren Thryothorus eisenmanni, Cuzco Brush-Finch Atlapetes caniceps and Parodi’s Hemispingus Hemispingus parodi. Those who planned Peruvian conservation units did not have access to all this data and the focus has tended to be on sparsely populated and isolated areas where there are no conflicts of interests and thus created a bias for protecting widespread species. In many areas species are redundantly conserved, whereas many of the rarest and most localized species are left unprotected. Machu Picchu was protected because of its archaeological importance with birdlife not being an issue. Fortunately, for reasons outlined above concerning patterns of human settlement and the benign climates of the area, this may have been the reason for the presence of rare and endemic species in this region.

There are to date 423 species of birds recorded within the Machu Picchu Historical Sanctuary, a very high avian diversity. Many are declining due the disturbance or destruction of their habitats by factors such as uncontrolled burning of the montane forests. Some are threatened, vulnerable or have small geographical distributions. It is fortunate indeed that a protected area, originally designed to protect archaeological remains, in fact also protects intact montane and elfin forest, fragmented Polylepis patches and a wonderful avian diversity.

 

Bibliography

Chepstow-Lusty, A.J., Bennett, K.D, Fjeldsa, J., Kendall, A., Galiano, W., and Tupayachi, H.A.
When two worlds collide.
Comparing Human Impact on Fragile Ecosystems Before and After the Incas. Tawantinsuyu vol. 3: 127-134.

Walker, Barry and Fjeldsa, Jon.