Male and female birds of this wader are alike. This species can get confused with the Common Greenshank. The Marsh Sandpiper has a needle-like bill without an obvious pale base like that found in the common greenshank. Other differences include the common greenshank having a slightly upturned bill, being larger and more robust and when in flight only the feet extend past the tail. In the marsh sandpiper the legs and feet can be seen.

Marsh sandpipers breed in the Palearctic from 50° East to 120° East. After their breeding season has ended they migrate to their non-breeding ground which extend from 30° North from Mauritania and Sudan, southwards to South Africa and eastwards to India and Australia.

They start arriving in southern Africa from September through to November. Unlike many waders these birds leave earlier in January and February. It is estimated that the coastal population in southern Africa is 2000 birds but are far more numerous in the interior. A small number of one year old birds do overwinter in southern Africa.

These birds are found in a variety of wetlands from saline to freshwater pans through to dams and floodplain pools. They are also found in large estuaries such as the Breede River estuary where a few birds are seen on the mudbanks at low tide. They are usually found singly or in loose groupings of other waders such as those seen along the Breede: common greenshank, curlew sandpiper, pied avocet and black-winged stilt. So, keep an beady eye out when looking through birds on the mudflats.

They feed on aquatic insects and larvae (coleopterans and chironomids), small crustaceans, polychaetes (bristle worms) and molluscs. They catch their prey by mainly feeding in shallow water where they pick the prey from the surface. If feeding in deep water then these birds move their bill in a sweeping side-to-side (scything technique) motion. On exposed mudflats they lunge at their prey.

The oldest known bird is from Europe and was 7 years and one month old. The only recapture of a bird from southern Africa put the bird at 6 years old. They can fly up to 10-15 km to their night roosts.