The changing trade-off between food finding and food stealing in juvenile oystercatchers.

When juvenile oystercatchers, Haematopus ostralegus, first arrived on the wintering grounds in August and September, they regularly stole mussels, Mytilus edulis, from other, mainly older, oystercatchers. By October, however, juveniles stole far fewer mussels and found almost all their mussels independently for themselves on the mussel bed. Although stealing a mussel was always less profitable than taking a mussel from the mussel bed, a simple rate-maximizing optimality model showed that, in August and September, juveniles increased both their net and gross rates of energy intake by stealing because they were rather inefficient at foraging for themselves.