Although there are ancient references (19th century) as to the possibility of the nesting of the Audoinii gull in a place on the southwest coast (Sagres), its occurrence in Portugal was always considered more or less accidental during the 20th century.
In 2000 a first couple nested in a semi-industrial salinas of Castro Marim, in the following year a small colony with about 12 couples was established in the same place. Later, other salterns with the same characteristics (semi-industrial) were occupied in the Tavira area, having nested around 4 dozen couples until at least 2008.
From then on the first nesting records in the marshes of the Ria Formosa appeared, and the population gradually increased, although with somewhat reduced reproductive success rates; the colonies were abandoned in the salt marshes, a situation which we confirmed in 2020 through a survey in Castro Marim and Tavira, and no breeding couples were located. The breeding population is currently estimated at around 3,000 couples, concentrated exclusively in the marshes of the Ria Formosa (see aerial view).