Waders like this winter-plumaged Black-tailed Godwit Limosa limosa, seen here feeding on a Dorset salt-marsh, have evolved in such a manner as to be able to avoid direct competition for food with other similar birds. Each species has developed specialised characteristics that enable it to be able to seek out food in slightly different locations to its close relatives and there is a varied array of body sizes, bill lengths, shapes and leg lengths on display whenever you watch a mixed wader flock feeding in a muddy estuary. Each species probes to a different depth (although there is doubtless some degree of overlapping) and probably to some extent on different species of invertebrates which they are able to detect by touch using their surprisingly flexible (for the longer-billed species) and sensitive bills. Black-tailed Godwits are at the larger end of the size spectrum and they have long legs and long, slightly re-curved bills. In the UK the most likely confusion is with the Bar-tailed Godwit Limosa lapponica. As there are seasonal variations in plumage and the two species may be found sharing the same location it is rather helpful that the former has a white rump and black tail with black bars of feathers on its wings and tail and it is therefore much more striking in appearance when airborne. Inveterate birdwatchers tend to abbreviate their nomenclature to 'Blackwit' and 'Barwit' respectively! A good reference book and field experience are must-haves when learning about waders as there are many subtle differences to look out for. This bird was a particularly confidin