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Counts of Soaring Bird Migration at Bourgas

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DAILY COUNTS

The counts at Bourgas are carried out from 10 August till 31 October 2011. They are organized by Institute of Biodiversity and Ecosystem Researches at Bulgarian Academy of Sciences. The research is a part of International Counts of Soaring Birds in Western Palearctic.

Visual observation data for the present 2011 year are show here in tables for each previous day. Table 27 Sept, Table 28 Sept, Table 29 Sept, 30_Sept, 1_Oct, 2 Oct, 3_Oct, 4__Oct, 5_Oct, 6_Oct, 7_Oct, 8_Oct, 9_Oct, 10_Oct., 11_Oct., 12_Oct, 13_Oct, 14_oct, 15_Oct, 16_October, 17_Oct, 18_Oct, 19_Oct, 20_Oct, 21_Oct, 22_OctN, 23_Oct, 24_Oct, 25_Oct, 26_Oct, 27_Oct, 28_Oct, 29_Oct, 30_Oct, 31_Oct, Final_Results

Data could be used by windfarm managers, security services at airports, birdwatchers and other for short-term ornithological forecasts.

Project Leaders: Tanyo Michev and Lyubo Profirov. E-mail: tanyo@abv.bg, lovebird@techno-link.com.

Observers: Lyubomir Andreev, Assen Ignatov, Boyan Michev, Emo Stoynov, Miroslav Enev, Rusi Todorov, Plamen Arsov, Valentina Angelova, Vladimir Mladenov.

Sponsors:

Bulgarian Windenergy Association

Jetstreem LTD

Ecotan LTD

Electrawinds Bulgaria Plc

DETAILED DESCRIPTION

Migration counts at Bourgas Bay started in 1978 (Michev, Simeonov, 1981). Regular counts started next year and continued until 2003. The results are presented in British Birds, January by Michev et al. (2011) for five species of waterbirds and 33 species of raptors (http://www.britishbirds.co.uk/2011/01/14/british-birds-january-2011/). The mean number of migrating waterbirds logged in autumn during the survey was 161,448 individuals (max. 250,623 in 1999), and the corresponding figure for migrant raptors was 38,639 (max. 65,065 in 1990).

The data confirm that Bourgas Bay is one of the most important sites for monitoring the migration of soaring birds in Europe, and the most important for the autumn migration of several species, including White Pelican (Pelecanus onocrotalus) and Dalmatian Pelican (Pelecanus crispus), White Stork (Ciconia ciconia), harriers (Circus spp.), Levant Sparrowhawk (Accipiter brevipes), Lesser Spotted Eagle (Aquila pomarina) and Red-footed Falcon (Falco vespertinus). The data collected during 20 years of the Bourgas survey provide the opportunity to track long-term changes in the populations of migrant waterbirds and raptors in Eastern Europe.

In Bulgaria, the Black Sea coast plays an important role in the orientation of these migrant soaring birds, and the nature of the coastline near the town of Bourgas creates a significant bottleneck. From Cape Emine, the coast turns sharply west for 15 km, along the northern edge of Bourgas Bay; then, after a short southerly stretch, it turns west again for a further 20 km. The Black Sea reaches its westernmost extremity near the town of Bourgas and this is an ideal place for observing autumn migration. Beyond Bourgas the route diverges: some birds follow the coast while others continue inland.

Fig. 1.The eastern part of the Balkan peninsula (lighter colours) showing the location of the Danube Delta, Western Black Sea coast including Bourgas Bay, the Bosporus and Dardanelles. Fig. 2. Map of the Atanasovsko Lake with migration watchpoint. Fig. 3. ViaPontica Map

Fig. 1 Shema ViaPonticaF

Reports on the migration of soaring raptors using the Western Black Sea flyway at the Bosporus were published in the late nineteenth century (Alleon & Vian 1869, 1870). Subsequently, observations covering the whole migration period there were documented by Porter & Willis (1968), Beaman et al. (1975), Robel & Brauning (1992) and Bossche & Lens (1994). In Bulgaria, Patev (1930, 1950) made an early attempt to find a similar watchpoint where soaring birds became concentrated (see also Baumgart 1971), while some details of the raptors migrating through the Bourgas area were given by Prostov (1964), Koenigstedt & Robel (1978), Laine (1978) and Donchev (1980). Kumerloeve (1957), Roberts (1979) and Michev & Simeonov (1981) made the first quantitative observations near Bourgas. Further south, there have been a number of important studies of the autumn migration of soaring birds by ground-based observers in Israel, but the ten-year survey reported by Alon et al. (2004) provides a convenient comparison for our data from Bourgas.

METHODS

A complete autumn migration survey was carried out from an observation point at Lake Atanasovsko, close to the town of Bourgas, from 1979 to 2003. Lake Atanasovsko forms part of the largest wetland complex in Bulgaria: a system of four lakes, with a total area of some 9,000 ha, all of which are designated as RAMSAR sites and IBAs, and form part of the European Natura 2000 Network.

Complete survey coverage, from 10th August to 31st October, was possible in most years from 1979 to 2003. However, there was no coverage in 1994–95 and only partial coverage in 1997, 2000 and 2002, and the results from those years are omitted here. During the survey, over 150 ornithologists, both professional and amateur, participated in the observations.

Visual observations were carried from the same place throughout the survey, on the eastern shore of Lake Atanasovsko (42º33’32.67’’N, 27º29’17.98’’E). When weather conditions were favourable, it was possible to monitor migration across an 8-km front of the flyway for the larger species.

The observations have been made using methods for monitoring of soaring birds:

http://www.moew.government.bg/recent_doc/biodiversity/Metodika_VEP.pdf

Data collected included number of individuals, time, distance and direction from the watch point, direction, height and character of flight. Direction of flight, as well as an estimate of distance from the watch point, was determined using particular landmarks at known distance/direction. The height of flight was estimated visually. When possible, migrant flocks were counted in tens or hundreds, while the larger flocks of storks and pelicans were estimated in gliding flight. Whenever possible, repeat counts of the same flock were made and the mean noted. We believe that count accuracy of the estimates of larger flocks is within 10–15% of the actual numbers. During 2011 research instrumental assessment of migrants number and altitude were applied for the first time in Bulgaria.

In 1982 and 1983, radar observations were undertaken, using the Plessey radio locators with four diapasons, situated at 15, 30, 60 and 120 km from the international airports at Bourgas and Varna. The radar observations ran simultaneously with the visual counts. With the help of observers at Varna airport, Cape Emine and Bourgas Bay (fig. 1), it was possible to obtain precise data on the migration routes, speed, height and size of the some migrating flocks (Michev et al. 1987; Simeonov et al. 1990) (Fig. 3).

Crispus B_buteo Tochkata Ponocr P_crispus A_heliaca

Pelecanus crispus with yellow ring M688 and Aquila heliaca with radiotransmitter. Where they come from?

Photographs by L. Andreev and A. Ignatov;

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Last modified 08.01.2012 07:14
 

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