Swennen C. (1990) Oystercatchers feeding on giant Bloody Cockles on the Banc d'Arguin Mauritania. ARDEA 78 (1-2): 53-62

Oystercatchers Haematopus ostralegus wintering in Mauritania were found to belong to the subspecies ostralegus. They probably came from Central and N. European breeding sites. The main food of the Oystercatchers was the Giant Bloody Cockle Anadara senilis of which the fresh mass of large specimens was as much as that of the predator itself. It is probably the largest common prey taken by any wader. The prey was opened by 'stabbing'. The birds did not select for size. Handling took up to 12 min. It was not clear how the birds were able to open the shells without the bills becoming squeezed between the two strong valves. The Oystercatchers opened on average 1.6 Bloody Cockles per h of low tide (22.6 per day). Half of the flesh was lost to kleptoparasites, mainly Lesser Black-backed Gulls during daytime and Grey Plovers at night. None of the other bird species were able to open the solid bivalves by themselves. Actual intake of the Oystercatchers was estimated at 37.1 g AFDM d-1 (848.8 kJ d-1); annual predation pressure was estimated at 8% of the standing stock of cockles.