In order to help resolve the problem of the birds' identity John Cox collected two specimens, one in 1975 and another in 1977, and deposited them at the South Australian Museum.

[3] Following Parker's description, the view that these birds represented a good species (as opposed to aberrant individuals or hybrids) gained some ground; the "species" was listed in the Shorebirds volume of the Helm Identification Guides,[4] for example, although with a note indicating that the possibility of hybrid origin could not be ruled out.

The bill is fairly long, blackish and slightly drooping, sometimes with a yellowish base; the legs are dull brownish-green in colour.

When hints of a breeding plumage are acquired, a rusty tinge develops on the breast and ear-coverts, some flank streaks appear, and on the upper parts the non-breeding-plumaged feathers are replaced by feathers with black centres, grey tips and buff or pale chestnut fringes.

When John Cox examined slides of the specimen in February 1988, he found a number of features in common with the Australian birds.

The birds appeared to be of the same size and structure, with several plumage features in common including a heavily streaked head and neck with a rusty wash, a split supercilium, and identically-patterned upperparts feathers.

[clarification needed] Nonetheless, those that have directly compared the Cooper's and Cox's sandpipers feel that they are not identical.

[2][5][6][7] In late August, 2001, another juvenile Calidris showing features of both pectoral and curlew sandpipers was found at Shintone, Ibaraki Prefecture, Japan.