Purple Sandpiper
Calidris maritima
Adults have short yellow legs and a medium thin dark bill with a yellow base. The body is dark on top with a slight purplish gloss and mainly white underneath. The breast is smeared with grey and the rump is black. They measure 20–22 cm (7.9–8.7 in) in length and 42–46 cm (17–18 in) across the wings, and weight is from 50–105 g (1.8–3.7 oz).
ID text from Wikipedia, CC BY-SA 4.0
White-rumped Sandpiper
Calidris fuscicollis
The white-rumped sandpiper is a relatively small bird measuring only 15–18 cm (5.9–7.1 in), with a wingspan of 36–38 cm (14–15 in). The top of its body is a dull grey-brown colour and it has a white eye stripe. Its beak is of medium length, thin and dark, and its legs are very dark. This bird is often mistaken with many similar-looking sandpipers that live in its range or along its migration path. The plumage is much less distinct during the winter; however, during all seasons males and females remain similar in their appearance. Voice: One of the white-rumped sandpiper vocalizations consists of a repeating "pip, pip, pip …" Their call has a distinctive metallic "tzeep" note which makes them easily identifiable among a flock of shorebirds. It resembles the sound of two pebbles scraping against one another.
ID text from Wikipedia, CC BY-SA 4.0
Where you might meet both
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