This paper reports a successful case of double brooding by the Great Bittern Botaurus stellaris, and its possible implications for both reedbed management and our understanding of male song patterns Double brooding is unusual in ardeids of temperate areas, but in tropical regions two or even three clutches have been recorded for a few species, especially smaller herons [del Hoyo et al. 1996). The laying of more than one clutch has only been recorded for nine species, none of which are large bitterns.

Great Bitterns, hereon referred to as Bitterns, have been reported to produce only one brood per year, and replacement clutches have never been recorded (Cramp & Simmons 1977, Voisin 1991). Zimmermann (1931) found empty nests apparently built for replacement clutches, but he did not find one that was subsequently used. However, Bitterns do have a long breeding season with eggs laid from March to early July (Cramp & Simmons 1977) Non-flying young have been found as late as September (Percy 1951), which suggests that replacement clutches, and even double brooding, are possible. Puglisi et al.(1 997) suggested that an observed double peak in booming activity by male Bitterns was inconsistent with the function of the boom being for mate attraction; they did not consider Bitterns to be doublebrooded, or that they might frequently replace lost clutches.