Pectoral Sandpiper
Calidris melanotos
This bird looks similar to the widely sympatric sharp-tailed sandpiper (C. acuminata), which is not however a member of the same clade in the genus. The pectoral sandpiper is a largish calidrid (19–23 cm (7.5–9.1 in) in length, with a wingspan of 37–46 cm (15–18 in)) with a grey-brown back, brownest in the summer male, and greyest in winter. The pectoral sandpiper has a grey breast, sharply demarcated at its lower edge, which gives this species its English name; this clear dividing line is particularly conspicuous if the birds are turned towards the observer.
ID text from Wikipedia, CC BY-SA 4.0
Semipalmated Sandpiper
Calidris pusilla
It is a small sandpiper, 15–18 centimetres (6–7 inches) long and weighing around 18–51.5 grams (0.63–1.82 ounces). Wingspan ranges from 13.8 to 14.6 in (35 to 37 cm). Adults have black legs and a short, stout, straight dark bill. The body is dark grey-brown on top and white underneath. The head and neck are tinged light grey-brown. This bird can be difficult to distinguish from other similar tiny shorebirds, in particular the western sandpiper; these are known collectively as "peeps" or "stints". Jonsson, Lars & Peter J.
ID text from Wikipedia, CC BY-SA 4.0
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