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

FENYŐSI L.: STUDIES OF AVIAN COMMUNITIES 127 Table 7.: Results of population estimations between Drava river kilometres 236-199, in 2002 and 2004 Species 236-229 river km 229-199 river km Total Species 2002 C. dubius 8-10 40-60 48-70 A. hypoleucos 2-4 10-15 12-19 A. hypoleucos 2004 C. dubius min. 17 30-45 47-62 A. hypoleucos min. 8 min. 16 24 Actitis hypoleucos and Charadrius dubius nesting population survey on the Drava section between Őrtilos (236 river km) to Bélavár (199 river km) For the more exact knowledge of Actitis hypoleucos and Charadrius dubius nesting populations, we also surveyed river sections outside the monitoring area - between 236199 river kms -, and made censuses and population estimations. The results are presented in Table 7. As a summary of corresponding surveys, the Charadrius dubius population on the entire Hungarian-Croatian section of river Drava between Ortilos (236 river km) and Bolhó (180 river km) can be estimated to at least 100-120 pairs, and the Actitis hypoleucos population to at least 30-40 breeding pairs. We believe that the stable populations of these bird species represent serious nature conservation values. The monitoring of Riparia riparia (and Merops apiaster) populations The monitoring area is the Drava section between Bélavár and Szentborbás (betwen 199 river km to 133 river km), where all the colonies on both the left and right side of the main river branch were surveyed each year. Nest hollows were counted, and, by assuming that 60% of hollows were occupied by nesting pairs (SZÉP 1991), their number was determined. Results are shown in Table 8. Population size in the sample area in the studied period was found to be as shown in Fig. 5. In the Drava section at 65 river km, the number of colonies varied between 7-12, and the number of breeding pairs ranged between 1116-2370. In the studied period the Table 8.: Results of riverbank surveys between Drava river kilometres 199-133, in 2000-2004 Year Number of colonies Number of Riparia riparia nest hollows Number of Riparia riparia breeding pairs Number of Merops apiaster breeding pairs 2000 12 3950 2370 14 2001 8 2540 1524 12 2002 12 1860 1116 5 2003 8 3265 1959 2 2004 7 2979 1787 23