sentences:  Egg hatchability (the proportion of viable eggs in fully incubated clutches) was 74% (n = 25 clutches), and the hatching success (the proportion of eggs that successfully become hatched young) was 63% (n = 48 clutches).A quarter of the nests were subject to nest predation both egg predation and nestling predation.More evidence is needed but it may be that after a breeding year, black harriers take a 'Sabbatical year" in reproduction to recover from the physiological stress of breeding.