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Oystercatchers Haematopus ostralegus (L.) arriving on their wintering grounds at the end of summer require there to be 6-8 times more mussel Mytilus edulis (L.) biomass available on their feeding grounds than they will consume over the winter if the birds’ normal high survival rate until spring is to be maintained: that is, their ‘Ecological Requirement (ER)’ is considerably larger than their ‘Physiological Requirement (PR)’. The ratio ER/PR was termed the ‘Ecological Multiplier (EM) and has been applied to a number of shellfisheries to calculate the Total Allowable Catch (TAC). The high value of the EM, however, has meant that mussel fisheries have suffered from much reduced harvests and thus economic difficulties. This paper proposes two methods by which the TAC could be increased without any predicted impact on the birds. In the ‘roll-over’ approach, the surplus biomass remaining at the end of one month is harvested during the next. In the ‘delayed start’ approach, the EM is not set at the beginning of autumn but at the beginning of the winter, which is when birds begin to starve. The two approaches can be applied together and would enable many more mussels to be harvested than is currently allowed without reducing oystercatcher survival. In the test case presented here, the TAC over the winter could be increased from 5% to between 35% and 45% of the standing crop of mussels present in September when the birds arrive.

1. A combined empirical and modelling approach was used to investigate the value of a Pacific oyster reef to feeding shorebirds and to observe and predict the impact of reef clearance on bird populations in the Colne Estuary, a protected area in south‐east England. Macro‐invertebrate biomass and numbers of feeding birds were measured on a Pacific oyster reef, an adjacent uncolonized mudflat, and an area of mudflat that had been cleared of oysters 6 months previously. These data were used to parameterize an individual‐basedmodel (MORPH) to predict the impact of clearance of the reef on winter bird survival. Feeding success and intake rates of Eurasian oystercatcher, Eurasian curlew, and Eurasian common redshank were also recorded during the course of a winter. 2. Themacro‐invertebrate diversity and biomass within both the oyster reef and the cleared area were significantly greater than the adjacent uncolonized mudflat. The density and biomass of large invertebrate prey in the mudflat were low, yet the Pacific oyster reef hadmuch higher densities and biomass of large prey, especially annelids and shore crabs. 3. The winter assemblage of feeding birds differed significantly between each of the areas. The mean total number of feeding birds was significantly greater on the uncolonized mudflat; however, mean peak counts, feeding success rate and prey intake rate of Eurasian oystercatcher were greater on the reef. Significantly greater intake rates and feeding success rates were also observed on the reef for Eurasian curlew, a species of conservation concern. 4. Field data and model predictions show that Pacific oyster reefs can provide valuable supplementary feeding areas for some shorebirds, yet other species avoided the reef. However, as estuaries vary in available feeding resources, it is important that the value of reefs and their management is determined regionally.