Nesting Ecology and Breeding Success of Cinereous Vultures (Aegypius Monachus) in Central Mongolia

Publication Date

6-2004

Type of Culminating Activity

Thesis

Degree Title

Master of Science in Raptor Biology

Department

Biology

Supervisory Committee Chair

Mark R. Fuller

Abstract

There are a total of 22 species of vultures in the world. They belong to two quite unrelated groups, the Accipitridae and Cathartidae families. The 15 species of Old World vultures that belong to Accipitridae group are closely related to the eagles and buzzards in the Falconiformes, but the 7 species of New World vultures that belong to Cathartidae group vultures are descended from the ancient storks (Houston 1983, Mundy et al. 1992). All vultures are primarily scavengers, inhabiting a variety of interesting ecological relationships around the world, but in many cases little studied and threatened by changes occurring in their environment.

I studied the cinereous vulture (Aegypius monachus) in central Mongolia in 2002 and 2003. This Palearctic species is also known as the Eurasian black vulture, and it is the largest Old world raptor. Mass of males is 7,000-11,500 g (n=20) and females 7,500-12,500 g (n=21) (Brown and Amadon 1968). The species was formally listed as Globally Threatened in IUCN Red List of Threatened Species (Collar et al. 1994, Collar and Andrew 1988), and today its category has been changed to Near Threatened (BirdLife International 2000).

Until the last two centuries, cinereous vultures had a considerably larger population than today, which ranged from Western Europe and North Africa, through Europe, Middle East, and Northeast China (Brown and Amadon 1968, Gensbol 1984, Fargallo et al. 1998). At present, the cinereous vultures breed only in three places in Europe: mainland and Mallorca Island in Spain, and Greece (Houston 1982, Vlachos et al.1999, Heredia 1996, Erdogdu et al. 2003). The rest of the birds nest from Turkey and Crimea eastwards in across Central Asia into Mongolia. The cinereous vultures are generally regarded as chiefly resident (Brown and Amadon 1968), but some young, and probably some adult birds migrate and reach to India, China, Taiwan, Nepal, Japan and Korea for "winter" (del Hoyo et al. 1994, Fomin and Bold 1991, Inskipp and Inskipp 1991, Sibley and Monroe 1990, Brazil and Hanawa 1991, Gore and Pyong-Oh 1971, Forsman 1999, Satheesan 2000, Shagdarsuren 1983, Hansoo Lee and Paek Won Lee pers. comm., N. Batbayar and M. Fuller unpublished data).

The cinereous vulture has significantly decreased in numbers throughout its breeding range, most notably in Europe, and disappeared from many countries. The greatest decline occurred from the second half of the last century to the 1980s (Heredia 1996, Fargallo et al. 1998). There is a paucity of information about its distribution and abundance in most of its range. It seems that currently the range of this species has been segmented into two parts in the Old World. The first is the Western, or the Southern European breeding population of cinereous vulture, and it consists of approximately 2000 pairs (Vlachos et al. 1999, Tewes et al. 2003). In Europe the major causes of the decline were pesticides, poisoning, illegal killing, and removal of their food supply due to changes in farming methods, and the habitat alteration in the breeding areas related to forestry operations, which facilitated access to formerly inaccessible areas and caused disturbance to the breeding pairs (Houston 1982, Heredia 1996). At present, this species has been regarded as one of the Europe's most threatened raptors and requires intensive management and conservation efforts (Wilbur 1983, Heredia 1996).

The second part of the species distribution is the Eastern, or the Asian nesting range where the rest of the cinereous vultures still live in relatively "normal or less threatened" situations. The species breeding range extends from Turkey and Caucasus Mountains in the west to Mongolia and northeastern China in the east, along the mountains in arid and semiarid steppe, grasslands and mountain areas that provide wide range of breeding habitats for cinereous vultures (Meyburg and Meyburg 1983, 1984, Kozlova 1933). The species status remains uncertain here due to very limited research. Also, the threats to cinereous vultures in Asia are still not fully clear; according to Xiao Ti (1991) many vultures are trapped, poisoned or shot for the trade in their feathers in China. In addition, we have evidence of shooting in Mongolia, and poisoning in China and South Korea. This species is listed variously throughout its range as an endangered or threatened species, and it is in Red Data books for rare and endangered species. However, the cinereous vulture is not listed in the Red Data Book of Mongolia or other environmental legislation because it is considered a common species in Mongolia. Indeed, the literatures about cinereous vultures in other countries suggest that, today, compared to historically, a much larger portion of the cinereous vulture distribution range exists in Mongolia. But there has been no systematic study for the cinereous vultures in Mongolia. Thus, there was a need to study the general ecology of cinereous vultures in Mongolia, which is an extensive refuge for the species that is endangered elsewhere.

To understand what supports and limits bird populations within the habitats they occupy, it is helpful to distinguish between the environmental factors (e.g., resources, competing species, weather, human impacts, and natural enemies) that influence populations and the demographic features (e.g., rates of birth and death, immigration and emigration) that those factors affect (Burnham and Cade 1995, Newton 1998, Marzluff and Sallabanks 1998). Particular populations may be affected by more than one of these factors, but sometimes one factor may be of prevailing influence at a given time.

Old World vultures, including the cinereous vulture, are exclusively scavengers, totally dependent on finding carrion. Generally, vultures are different from non-vulturine raptors in respect to food habits, nesting density, and distribution. For example, usually they do not aggressively hunt for prey, and do not hold fixed feeding ranges (Houston 1974, Mundy 1990, Brown and Amadon 1968). While some of the large vultures nest in colonies of over one hundred nests, others nest in loose colonies, or solitarily (Brown and Amadon 1968, DelHoyo et al. 1994, Houston 1974 and 1983, Mundy and Ledger 1976, Fargallo et al. 1998). Newton (1979) and Houston (1974) stated that nesting dispersion of the Old World vultures depends mainly on the proportion of large-carcass carrion in the diet, and on the distances flown from the nest. They can forage far distances from the nest or roosting sites compared to non-vulturine raptors. Their food (carcasses of animals) is unpredictable and temporary, and birds might need to search large areas to locate dead animals (Bahat 1999, Boshoff et aL 1984, Guzman and Jimenez 1998, Houston 1974, Mundy and Ledger 1976). This dependency has led to a foraging strategy based on minimizing the energy costs of searching and maximizing the range of foraging flights (Brown and Amadon 1968, Newton 1979, Houston 1974, Pennycuick 1972, Hiraldo and Donazar 1990).

Factors that limit raptor population take account of several conditions that affect habitat suitability, reduce survivorship of young or adults, or decrease nesting success and productivity of breeding pairs. Some factors have relatively short-term affects on populations or cause the populations to fluctuate from year to year, whereas some factors, many of them linked to human activities such as contaminant levels, habitat degradation or loss, and nest site disturbance, have long-term effects on species (Newton 1998).

My study goal was to understand ecological factors that affect cinereous vulture nesting distribution and abundance in central Mongolia. Some aspects of cinereous vulture breeding ecology have been well studied in Europe (Hiraldo and Donazar 1990, Hiraldo 1983, Snow and Perrins 1998). But, the information about cinereous vultures in Mongolia and most parts of Asia, are in the form of brief field observation notes and accounts. I studied cinereous vulture nesting habitat, and the association between habitat use and nesting success. My study area was composed of locales of different protection status, different topography and vegetation, and different livestock and wild ungulate numbers. These differences might influence vulture nesting site choice, productivity, foraging activity and diet. I predicted that livestock provide the majority portion of food supply for cinereous vultures compared to wild animals in central Mongolia. Livestock likely is the most available carrion source to vultures in Mongolia. It was important to understand the breeding performance of cinereous vultures in different areas and the environmental factors that might affect the population.

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