Green sandpipers are starting to appear in ones and twos at the edge of freshwater pools. They are coming down from northern Europe, and these first birds are probably from Finland. They are also probably females, who often leave their chicks in the care of the males.

They are medium-sized waders with quite long legs, and their hind quarters bob up and down as they probe the mud in shallow water. Their back is dark brown, with a faint green gloss that you can hardly ever see, but it looks almost black by contrast with their shining white underparts.

One often spots them first when they fly up. They have a white rump which, with the dark back, makes them look like large house martins. They go up almost vertically, making a distinctive triple cry with a melancholy air to it. But it is worth waiting after they have disappeared over the horizon. If they have found a good feeding place, they will circle round and suddenly dive out of the sky again to resume wading just where they left off.

Unlike most waders, which on migration stop to feed along the coast or on estuaries, green sandpipers travel across land and like feeding in fresh water.

They will come down at any inviting pool that they see below them. I have several times found them at small ponds in parks. Once I flushed a pair from the edge of a small river that ran between two fields in farmland. They were on a muddy patch where cows had come down to the water to drink and had trampled down the bank. They quickly came back again.

Even on estuaries, you do not find them out on the mud and sand, but in the shallow dykes behind the seawall. They can drop in almost anywhere in Britain in July and August, and on bird reserves where there is a “scrape” — a shallow stretch of mud and water deliberately created to attract ducks and waders, generally with a hide beside it — there is a very good chance of seeing them. They can stay here for a month or two, taking it easy in the summer weather, before moving on south.

A pair has occasionally nested in Scotland. But they breed mostly in the boggy forests of the far north of Europe and Asia. Most unusually for a wader they nest in trees. But they do not make their own nests. They use old thrush or woodpigeon nests, and sometimes will even lay their eggs on a comfortable clump of witches’ broom.

What to look out for

Juvenile cuckoos are out and about in their dark, streaked plumage, and spied singly at a distance may be mistaken for a small bird of prey. But at this time of the year they are more often to be seen in most unraptor-like fashion, hanging out somewhat aimlessly together in small parties on overhead wires

Details from Birdline, 0906 8700222 (60p a min)