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Environmental Studies |
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GPS tracking of bearded vulture: Conservation of Gypaetus barbatus of Crete Remote GPS fix data download via UHF communication link |
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by Stavros Xirouchakis |
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The Project: The goal of this pilotproject is testing if bearded vultures (Gypaetus barbatus) can be tracked via GPS units. The present study is part of conservation project titled “Conservation of Gypaetus barbatus and Biodiversity of Crete” implemented in all mountain regions of Crete. It is carried out by the NHMC of Crete University in collaboration with the Forestry Services and is financially supported by the European Union under the funding instrument of LIFE-NATURE. The project’s main objective are: a) the regular breeding of reproductive pairs and the augmentation of juvenile survival through a supplementary feeding scheme and b) a large scale public awareness campaign in order to establish the Bearded Vulture as the flagship species of mountainous Crete and forestall illegal shooting. The region of Agios Dikaios (Municipality of Innachorio, Prefecture of Chania) harbours one of the remaining breeding pairs of the island which breeds successfully since 1998 after the establishment of a feeding station in its territory. During the breeding period 2004-2005 the earliest clutch in Europe was recorded with the first egg being laid in 10 October 2004. The chick hatched after 55 days at 4 December 2005 and fledged after 120 days. She spent its first night away from the nest at 16 April 2005.
Preliminary results of conventional radio tracking in previous years of the chicks born in the Agios Dikaios territory revealed that young Bearded Vultures: · remain in an area when food is available until they consume it · forage 12-15 km from roosting site · often follow Griffon Vultures that aggregate in large numbers over carcasses. · prefer to forage in regions with low adult density.
However conventional radio tracking failed to provide us with information on the exact period of abandonment of the natal territory and the initiation of the long range movements of the birds. Moreover there have been gaps in the routes followed in certain massifs by the radio-tagged individuals, as the location of young vultures in the numerous gorges of the island has proved difficult.
Figure 1: Climbing to the vulture’s nest
So a GPS unit was harnessed in the chick that fledged in 2005 in order to investigate the pattern of its post fledging dispersal and the habitat use during its first year of life. We used Teflon-treated ribbons to fit the 167 g light weight GPS-device on the back of the vulture (figure 1, 2 and 3). The GPS-unit is equiped with activity and temperatur sensors and a traditionall VHF-beacon. The GPS-data can be downloaded via UHF-link by a small Handheld Terminal. The GPS-receiver are programmed to take 3 fixings per day, which results in a 1 year lifetime of the unit.
First results The bird spent almost the first month after fledging in the vicinity of the nesting territory depending from its parents for food. In May she followed her parents in the feeding station of the area and in June (two months after fledging) she abandoned the natal territory wandering in the adjacent mountains and settled in the region of Lefka Ori. During the last few months the young vulture has been observed around the Samaria National Reserve (figure 4).
F i g . 4 : G P S localization points of a young bearded vulture in Greece, Crete 2005
More information: The Bearded Vulture a territorial cliff nesting raptor, dweller of the high mountains. It inhabits almost exclusively mountainous regions (mostly above 600m) with valleys and high peaks where traditional pastoralism is being practiced or a good population of medium-sized wild ungulates still occurs (in the case of Crete the Cretan wild goat Capra aegagrus in the National Park of Lefka Ori). During summer birds forage (singly or in pairs) over extensive upland areas covering several square kilometers with sub-alpine vegetation. In winter and early spring they exploit middle altitude areas with steep-cliffs and rocks free of snow. The species has unique feeding habits, eating bones which are swallowed whole, while larger ones are dropped from a height on rocky slopes so they break apart, and are consumed as pieces. In Greece virtually all food comes from livestock while birds use local waste dumps where carcasses of domestic animals are disposed. The Bearded Vulture was widespread almost in all mainland massifs of Greece till the late 1980s. Since then it has undergone a dramatic decline due to the excessive use of poisoned baits set for vermin (mainly wolves, Jackals and foxes), direct persecution by man and food scarcity caused by the decline of nomadic pastoralism. At present the species breeds only on the island of Crete where it has been favored by the extensive pastoralism and the rugged terrain of the island that offered him suitable foraging habitat and ample nesting opportunities. In addition the low use of poisoned baits, as large carnivores are absent from Crete has been the key factor for its survival. At the moment the species population numbers 25-28 individuals or 5 breeding pairs, a fact that make it the most rare vertebrate in the country. The species is an early breeder in Crete nesting in late October–mid November. Nests are placed in potholes (46%) small caves or inaccessible ledges in cliff walls in middle altitude areas (mean=750 m, range= 280-1450m) close to the herds’ wintering grounds. Although the two-egg clutch is common, only one chick survives. The young stays at nest for about 120 days and normally fledges in May.
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