Cox's Sandpiper (Calidris × paramelanotos) is a hybrid between a male Pectoral Sandpiper (Calidris melanotos) and a female Curlew Sandpiper (Calidris ferruginea). First discovered in Australia in the 1950s, it was originally described as a species new to science and named after Australian ornithologist John B. Cox. However, it was later found to be a hybrid. Most if not all birds found to date are males, in accord with Haldane's rule. Discovery and naming The first Cox's sandpiper was recorded in Australia in 1955. Observers initially identified the birds as Dunlins (Calidris alpina), but as additional birds were discovered — particularly in the period between 1968 and 1975 — doubts were cast on the initial identifications. By 1986, at least 20 such birds had been observed along the continent's southern and eastern coasts, though no consensus existed about their identity; among the theories postulated were that the birds were aberrant individuals or a previously undescribed subspecies of the Dunlin, or that they were a stereotyped hybrid (meaning that all birds of some hybrid parentage appear near-identical). 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. Thinking that the birds might be "Cooper's sandpipers" (see below), the two specimens were sent to the American Museum of Natural History in 1977 for comparison with the type specimen from which that form was named; replies indicated that the birds were not of the same species. A live bird was caught and photographed in 1981, and, in 1982, Shane Parker formally described the bird as a new species. 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, for example, although with a note indicating that the possibility of hybrid origin could not be ruled out. Appearance Cox's Sandpipers are similar in size and shape to Pectoral Sandpipers and Sharp-tailed Sandpipers (Calidris acuminata). The bill is fairly long, blackish and slightly drooping, sometimes with a yellowish base; the legs are dull brownish-green in colour. The birds' wings at rest extend just slightly beyond the tail. Cox's Sandpiper has never been observed in breeding plumage. All mature specimens that have been observed have been in non-breeding plumage, although