Ábrahám Levente: Biomonitoring a Dráva folyó magyarországi szakasza mentén 2000-2004 - Natura Somogyiensis 7. (Kaposvár, 2005)

Fenyősi, László: Studies of avian communities along river Drava, between 2000-2004 (Aves) - Madárközösségek vizsgálata a Dráva somogyi szakasza mentén, 2001-2004-ben

134 NATURA SOMOGYIENSIS Table 15.: Occurring waterfowl species and their specimen numbers in the Drava section between river kilometres 199-184, in 2004 Species 27/01/2004 15/02/2004 04/09/2004 15/10/2004 17/11/2004 07/12/2004 Tachybaptus ruficollis 4 6 3 5 5 Phalacrocorax carbo 13 56 59 20 65 Egretta alba 10 7 1 2 6 Ardea cinerea 3 5 5 2 6 Cygnus olor 12 6 2 3 6 Anas penelope 22 Anas crecca 30 8 4 60 Anas platyrhynchos 2130 1085 10 190 280 980 Ay thy a ferina 6 Aythya fiiligula 1 Bucephala clangula 4 4 Haliaeetus albicilla 2 1 1 Fulica atra 1 Tringa nebularia 2 Tringa ochropus 1 2 Larus cachinnans 1 Total 2228 1176 14 268 311 1139 The monitoring of white stork (Ciconia ciconia) populations The sample area along river Drava selected in 2000 is made up of 17 village districts between Ortilos and Bares. The extent of the area including both outskirts and inner village areas is 511 km2. During the surveys we also visisted, in addition to nests inside the villages, those few that are located in the outkirs. The following abbreviations and parameters are used for presenting the results: CO FTX: uninhabited nest HPo: unsuccessful nesting HE: solitary individual HPm: successful nesting HPa: number of breeding pairs JZG: number of young birds leaving the nest The most notable findings of the surveys between 2000-2004 are presented in Figures 9-10. From Fig. 9 it appears that between 2000-2004 the number of nesting pairs (Hpa) decreased from 58 to 45 (by almost 20%). Associated with this trend, the number of uninhabited or abandoned nests (FIX) in the same period grew to fivefold the initial value (increased from 3 to 15). The number of young birds leaving the nests varied between 79-108 in 2000-2004 (Fig. 10). It is seen from Fig. 10 that the high number of fledgelings in 2000 is unparalelled in the rest of the study years. The rate of successful (Hpm) vs. unsuccessful (Hpo) nestings in the studied period appeared to be balanced, with minor fluctuations (Fig. 10).