Shorebird feed
from the above it is clear that the physical composition of the sediment influences the numbers of shorebirds feeding upon it, but within a suitable area of mud it still known precisely what attracts birds to one part of a beach and not to another. there are clues, however. small ocypode crabs, prawns, fish larvae, polychaete worms and small bivalves are among the most important foods for shorebirds and the distribution of these foods between beaches is very uneven. Differences in the fauna in mudflats can really only be determined by direct investigation (Swennen and Marteijn 1985). where suitable prey is present, density is the most important factor, followed by prey size, prey depth and the penetrability of the substrate (Myers 1980).
Tidal state, wind and disturbance all affect the density and availability of prey, and this is why certain beaches are only used by the waders at certain times (Evans 1976; Grant 1984). Casts of mud thrown up by susupension feeders and swimming movements of small crustaceans are visual clues for the birds, showing them where to feed (Pienkowski 1983), but some birds use tactile rather visual clues and have sensitive beak tips which can sense prey underground. Sandpipers, one group of partially tactile feeders, may avoid sandy mud because the sand grains are very similar in size to the polychet and oligochaete worms upon which they feed (0,5-1 mm) (Quemmen 1982).
Tidal state, wind and disturbance all affect the density and availability of prey, and this is why certain beaches are only used by the waders at certain times (Evans 1976; Grant 1984). Casts of mud thrown up by susupension feeders and swimming movements of small crustaceans are visual clues for the birds, showing them where to feed (Pienkowski 1983), but some birds use tactile rather visual clues and have sensitive beak tips which can sense prey underground. Sandpipers, one group of partially tactile feeders, may avoid sandy mud because the sand grains are very similar in size to the polychet and oligochaete worms upon which they feed (0,5-1 mm) (Quemmen 1982).