Especially from a distance the Common Ringed Plover (Charadrius hiaticula) may be confused with the Little Ringed Plover (Charadrius dubius).
However, the adult Common Ringed Plover has an orange bill with a black tip and no eye-ring, whereas the Little Ringed Plover has a black bill and a yellow eye-ring.
Juvenile Common Ringed Plovers (1st and 2nd photo) have a black bill, the markings on the chest and head are more brownish than black, they have dull yellowish-grey legs and they often have an incomplete grey-brown breast band.

1st & 2nd photo: Alvor Estuary, Alvor, Algarve, Portugal, 27 November 2017
3rd & 4th photo: Sitio das Hortas, Alcochete, Tagus Estuary Nature Reserve, Portugal, 12 October 2021
5th photo: Ria Formosa National Park, Algarve, Portugal, 18 November 2017