REPRODUCTIVE-BEHAVIOR OF AQUATIC WARBLERS ACROCEPHALUS-PALUDICOLA IN CAPTIVITY

Breeding behaviour of four hand-raised Aquatic Warblers has been studi ed in captivity. Two females produced fourteen clutches in 1991-94. Th e behaviour of early stages of the breeding cycle of this promiscuous sylviid warbler, which is one of the rarest passerine birds in the wes tern Palearctic, could never been observed in the wild up to now. Both females built their nests within 3-5 days, being most active during e arly morning and in the evening. Nestbuilding strongly stimulated the copulation activity of two males. Each of the two males continuously a ttempted to copulate with the females during their fertile periods. Bo th females repulsed almost all of the copulation attempts and hit in t he vegetation. The duration of mountings was unusally long (xBAR = 23. 7 +/- 11.8 min; n = 31). Between cloacal contacts the male remained on top or directly behind the female. Incubation (from laying of the las t egg until hatching of first young) lasted 12 (two cases) and 14 days (one case). The interval between loss of a clutch and laying the firs t egg of the next clutch was 7 days (median; n = 7). In case of a secr etive and unobtrusive species being hard to observe in the wild like t he Aquatic Warbler, studies of captive birds can provide an effective tool to understanding important aspects of their biology.