BROOD PREDATION HABITAT CHARACTERISTICS AND NESTING DECISIONS IN ACROCEPHALUS-SCIRPACEUS AND A-PALUSTRIS

Reed habitats are characterised by a gradient of increasing vegetation density and decreasing prey abundance. We examined tile effect of nes t predation on nest site selection and parental investment in relation to this gradient ill two closely related warbler species. The marsh w arbler Acrocephalus palustris and the reed warbler A. scirpaceus have to contend with this ecological gradient but, tile distribution along this gradient differs between them. To examine whether this affects ma ting strategies of the two species differently we looked at i) differe nt vegetation features between depreciated and non-depredated nests in both species, ii) female preference of safe nest sites for territory or male quality; and iii) male parental investment. In monogamous leed warblers there is no relationship between nest cover and predation. U sing start of egg-laying as an index for female preference, we only fo und a correlation with paternal feeding, but not with nest cover, This suggests potential female choice for male quality since male care was independent of food abundance anti correlated with early egg-laying b y females. Also, reed warbler males actively defended tile nest to a c ontrolled observer approach. In the opportunistically polygynous marsh warbler, there is a negative correlation between nest cover and blood predation. Furthermore, female start of egg-laying correlates with ne st cover (i.e. safe nest sites) whereas there is no relationship betwe en male feeding and start of egg-laying. This suggests female preferen ce for nest site duality. Paternal quality for female choice is propos ed to be less extensive clue to tile lack of relation between start of egg-laying and male feeding care, and because males generally did not actively defend tile nest to a controlled observer approach.