Habitat associations and breeding success of yellowhammers on lowland farmland

1. Yellowhammers began to decline on British lowland farmland in the late 1 980s and losses are presently 10% per year. This study examined variation i n the habitat selection and breeding success of yellowhammers, allowing an evaluation of whether Britain's yellowhammer decline might have been caused by recent changes in agriculture. 2. Yellowhammer territories were associated with hedgerows, vegetated ditch es and wide uncultivated grassy margins around fields. Pasture and silage l eys were avoided. Nests were built among herbaceous vegetation in ditches o r in the shrubby vegetation of hedgerows. 3. Breeding started slightly earlier on organic farms than on intensively m anaged farms, but no measure of breeding success differed between farm type s. Predation was the cause of most (64%) nest failures. A maximum of three breeding attempts (two successful) was observed per pair, with a mean clutc h size of 3.3, a Mayfield nest success rate of 0.46, and 2.6 nestlings fled ged per successful brood. These data, together with published estimates of adult yellowhammer survival and of post-fledging survival among other passe rines, suggest that breeding productivity is too low to maintain a stable p opulation. 4. The removal of hedgerows or abandonment of hedge management, filling or clearing of ditches, intensification of grassland management and cropping o r grazing right up to the field edge, are all likely to have adversely affe cted yellowhammers on lowland farmland in southern England. Policy reforms that redirect subsidy support to environmentally beneficial management of f ield margin habitats and retention of winter-feeding sites such as stubbles should assist in restoring populations of breeding yellowhammers on lowlan d farmland. 5. Our data expand further the array of farmland bird species for which int eractions between agricultural change and population change are increasingl y understood.