AGE-DEPENDENT CHOICE OF REDSHANK (TRINGA-TOTANUS) FEEDING LOCATION - PROFITABILITY OR RISK

1. The effect of a varying risk of predation by sparrowhawks (Accipiter nisus L.) on choice of overwinter feeding site was studied for redshank (Tringa totanus L.), on a small Scottish estuary at low tide. 2. Adult and juvenile redshank segregated into two areas, a mussel bed and a salt-marsh area, respectively. Juveniles were excluded from the mussel beds by the adults, but there were no aggressive interactions on the salt-marsh. Adults occasionally fed on the salt-marsh, particularly late in the winter. 3. A redshank on the salt-marsh was 4.8 times more likely to be killed on the salt-marsh than on the mussel beds. Redshank on the salt-marsh fed closer to cover, than those on the mussel beds: sparrowhawk attack success rate declined as redshank fed further from cover. 4. A redshank on the salt-marsh had a much higher foraging rate and overall energy intake rate (1.7 times) than a redshank foraging on the mussel beds. Adults on the mussel beds minimized risk of predation, rather than maximizing intake rate at low tide. 5. Despite higher energy intake rate anywhere on the salt-marsh compared to the mussel beds, juveniles on the salt-marsh fed very close to cover, and consequently at a greater risk of predation. Foraging rates were highest very close to cover. Although juveniles were forced to feed on the salt-marsh, they maximized intake, rather than minimizing predation with respect to choice of feeding location within the salt-marsh.