Small, dark Ringed Plovers, possibly of the Arctic race psammodroma, Black Rock, 3rd April 2014 (David O'Connor). There were two individuals present.
The race psammodroma is somewhat contentious. According to HBW, the populations of the race range from from Canada to the Faeroe Islands but have been based on extremely minor differences in average size, and are generally not accepted nowadays.
These darker birds, whatever subspecies they might be, are certainly distinctive in the field.