What predates on cockles?

Large snails and sea stars.

In Europe...

Many shorebirds and waterfowl will predate on the common cockle (Cerastoderma edule) occurring in intertidal areas. Perhaps the most important of these are oystercatcher (Haematopus ostralegus) and common eider (Somateria mollissima) feeding upon adult cockles, and knot (Calidris canutus) feeding upon spat (newly settled). There are also numerous invertebrate predators of cockle spat, such as the shore crab (Carcinus maenas) and the brown shrimp (Crangon crangon). These spat predators can seriously affect settlement success in some years. Record settlements of cockle in some areas after the 1962/63 cold winter was attributed partly to increased mortality and delayed migration of particularly invertebrate predators. Fish in estuaries, such as flounder (Platichthys flesus), will also feed upon small cockles, though fish predation is thought not to be as important as a mortality factor as bird and invertebrate predation.

As mentioned above, starfish can also be important predators of cockles of various sizes. This applies particularly to the common starfish (Asterias rubens) which can sometimes form huge swarms in estuarine areas and is considered a serious pest of shellfisheries.