Population state and breeding conditions of the Paddyfield Warbler on the northern coast of the Azov Sea. - E.A. Diadicheva. - Berkut. 5 (2). 1996. P. 163-166.
At present the Paddyfield Warbler became numerous breeding species on the northern coast of the Azov Sea, particularly on the accumulative spits, estuary (liman) banks and islands, in the mouth zones of rivers. This study have been carried out in the preserve of Stepanovskaya Spit (Zaporozhie region, Molochniy liman), where the Paddyfield Warbler is dominating breeding species of passerines. Phenology, breeding habitats, placing of nests, population density, breeding cycle, parameters of eggs and nests (Tab. 1) are described. The first Paddyfield Warblers were observed on 24.04-3.05. The earliest start of egg-laying was recorded on 23.05, the mass egg-laying - in the first decade of June, the beginning of hatching - on 10.06. Mean breeding density in the preserve is 10-13 pairs/ha. Ecological density in the reed and reed-wormwood habitats along the liman coast was 29 nests/ha in 1990-1991; 24 - in 1992; 10 - in 1993; 12 - in 1994. Three types of breeding habitats on the spit are characterized: reed growths along the liman coast and on the islands, reed-wormwood associations and tape reed lines along the canals. Mean clutch-size is 4,38 (4,0-4,69 ), most of full clutches contains 4-5 eggs. The incubation period lasts 14 days, fledglings leave the nest in 11-12 days after hatching (9-10 days in case of disturbance). Special attention was paid to breeding efficiency estimation. Different methods of breeding success calculation are compared (Tab. 3). Indices obtained by the Mayfield method are lesser than others but appear to be most realistic. Mean breeding success seems to be 38,9 % and in average about 1,7 fledglings per 1 breeding pair leave the nest during one breeding cycle. Eggs in clutches have perished owing to raptors activity; disturbance (resulting in abandoned nests, mostly during the egg laying); high level of embryonic death-rate (13-13,3 %); nest-parasitism of the Cuckoo (6-14 % of nests) and much more rarely - destruction of nest by flood or wind. The existence of 2 or even 3 breeding cycles is probable, taking into account the duration of breeding period (about 90 days) and one breeding cycle (about 26 days). The significant differences were found for the egg parameters, clutch size and breeding success of the Paddyfield Warbler populations on the northern coasts of the Azov Sea (Molochniy liman) and Black Sea (Tiligul liman). [Russian].
Key words: Paddyfield Warbler, Acrocephalus agricola, phenology,
population density, breeding, nest, clutch, egg, method, breeding success.