PREY ABUNDANCE AND MALE PARENTAL BEHAVIOR IN ACROCEPHALUS WARBLERS

This study examined the prey abundance at nesting sites of five differ ent Acrocephalus warbler species. Intraspecific variations in prey den sity were analysed to determine the relative significance of this ecol ogical factor for different mating systems and components of male pare ntal behaviour, The Great Reed Warbler Acrocephalus arundinaceus, a fa cultatively polygynous species, nested in areas with the highest insec t abundance. Its intraspecific variation in prey density (between diff erent territories) was the highest while the male : female offspring f eeding ratio was the lowest, At the other extreme, the monogamous Mous tached Warbler Acrocephalus melanopogon and Reed Warbler Acrocephalus scirpaceus nested in areas with the lowest prey abundance and lowest i ntraspecific variation, Males of these species had the highest involve ment in feeding young. In the Moustached Warbler and Marsh Warbler Acr ocephalus palustris, an intraspecific comparison revealed a negative c orrelation between insect abundance and the male feeding component; a tendency in this direction was found for the Reed Warbler, while no co rrelation was evident in the polygynous Great Reed Warbler. These data demonstrate a general pattern relating prey abundance, mating systems and male parental investment on an interspecific level, However, intr aspecific correlations revealed a net of complex interdependence. One of the factors which may be important is resource predictability, We f ound a significant correlation between certain vegetation types and in sect abundance, The vegetation composition of territories is further i nfluenced by interspecific dominance relationships whereby the dominan t Great Reed Warbler occupies territories with the vegetation type whi ch correlates with high prey abundance while the overlapping Moustache d Warbler and Reed Warbler are restricted to areas with lower insect d ensity.