Tuesday, December 18, 2012

ID Feature: Knots

Following on from one of our previous ID features on Pectoral Sandpiper identification (cf. Sharp-tailed Sandpiper), we now discuss the separation of another tricky wader pair; the two knot species, Great Knot (Calidris tenuirostris) and Red Knot (C. canutus). Both species are regular visitors to much of the Western Australian coast, with very large numbers occurring in the north at locations like Roebuck Bay, near Broome. Identification of the two species in breeding plumage is trivial (providing you’ve correctly identified the bird as a knot), but with the exception of northern areas early and late in the wader season, knots are not commonly encountered in breeding plumage in Western Australia.

Red Knot in breeding plumage (right), easily identifiable from Great Knot by extensive red on face and underparts.

Great Knot moulting out of breeding plumage, easily identified from Red Knot by extensive black breast markings and lack of red colouration on underparts.

Identification of birds not in breeding plumage can be more problematic, and these plumages are the most commonly encountered in WA, particularly in the south. The following features are useful for separating the two species in non-breeding plumage. Structural features mentioned below, like bill length, are still applicable in breeding plumage, but plumage features aren’t. Several plumage features are also applicable to juvenile plumage, generally mention will be made of differences. As always, there can be significant individual variation in many of the features mentioned here, so we advise observers to use a combination of features to confirm identity.

Great (left) and Red (right) Knot in non-breeding plumages, showing similarities and differences. Identification is generally easier in situations where the two species can be compared side by side. See end of Key Features section for an annotated version.