The Pectoral Sandpiper, Calidris melanotos, is a small wader. It is sometimes separated with other "stint" sandpipers in Erolia. These may or may not be a good monophyletic group depending on the placement of the phylogenetically enigmatic Curlew Sandpiper, though in any case the genus name Ereunetes was established before Erolia.
"Cox's Sandpiper" ("Calidris" × paramelanotos) is a stereotyped hybrid between this species and the Curlew Sandpiper. This does not prove a particularly close relationship between these two species, as far more distantly related waders have successfully hybridized.
The juveniles are more brightly patterned above with rufous colouration and white mantle stripes.
This species differs from the Sharp-tailed Sandpiper in its breast pattern, weaker supercilium and greyer crown.
It is a very long-distance migrant. The American and most of the Asian birds winter in South America, but some Asian breeders winter in southern and Australia and New Zealand. There is data indicating that the migration might be affected by global warming, as is suspected for many Arctic-breeding birds: 100 years ago, migrating Pectoral Sandpipers were observed to pass through northern Ohio in early-mid May and again in late August; today, the bulk of the northward migration takes place in April already, and most birds do not return until mid-September.
This species occurs as a regular migrant to western Europe, and is not considered as a rarity in Ireland or Great Britain. Many of the birds occurring in Western Europe may be on a regular migration from Asian breeding grounds to winter in Southern Africa. September 2003 saw a record influx to those two countries, with 40 found in Ireland, and 150 in Great Britain. While the Pectoral Sandpiper has not been recorded as breeding species in Europe, it has been found in Scotland in suitable breeding habitat in summer. On the US Pacific coast, such stagings of migrant flocks appear to be rarer.
This species nests on the ground, laying four eggs. The male has a display involving puffing up his breast, which has a fat sac in the breeding season to enhance his performance.