Last saturday I saw one Least Tern on the reserve of Punta Rasa, Buenos Aires province, Argentina. This is a vagrant because this Tern lives in the Caribbean area. It was one specimen in a group of aprox. 5000 Common Terns and Snowy-crowned Terns plus a few Royal Terns and Sandwich Terns.
Make sure that record goes to the loacl recorder! Well Done Fritz!