The breeding performance of Blackcap Sylvia atricapilla in two types of forest habitat.

The breeding densi ty of Blackcap was about four times higher in deciduous (D) riparian linear vegetation than in mixed (M) coniferous woodlots in the farmland of Eastern Bohemia, Czech Republi c, over two years. Laying started and peaked about two days later in M habitat, possibly because of delayed leafening of preferred nesting shrubs in forest undergrowth and consequently delayed availability of concealed nesting sites. No significant differences in egg size, clutch size, brood size, nest success (31%, n = 320nests, Mayfield method) an d mortality factors (predation ? 68%, n = 193 failed nests) were found between habitats or years . In all data pooled across years, the me an clutch size was marginally larger in D habitat. The minimum productivity was 1.4-2.2 fledglings territory 1 and did not differ consistently between habitats or years. The absence of a clear difference in reproduction despite large differences in breeding density is in line with the predictions of the ideal free distribution model

Weidinger K. 2000, Ardea 88 : 225-233