This marine IBA complements the current terrestrial IBA (PT033) and includes the main feeding areas for Little Terns in the marine areas adjacent to the barrier-island system of the Ria Formosa, which has features that are unique in the world (Dias et al. 2004). This IBA is also used by Audouin's Gull, an endangered species that is sparsely distributed in Portugal. The sandy lagoon body is surrounded by flat marshes, tidal channels and small muddy or sandy islands (Dias et al. 2004) This highly productive habitat is in fact an important spawning area for various species of fish (Erzini et al. 2002) and offers a mixed variety of potential prey for species such as the Little Tern. The alternative feeding habitats, such as tanks of lower salinity (from extensive salinas) are important, since they are not influenced by tides and winds (Paiva et al. 2006).
Audouin's Gull Larus audouini: One of the colonies for this nationally endangered species is located here, and its individuals are likely to use this marine area for feeding. The Castro Marim area (east of the IBA) holds the remaining Portuguese breeding population. (Leal & Lecoq 2005).
Little Tern Sternula albifrons: In this area, this species breeds in natural habitats (sandy beaches on the barrier-islands) and alternative habitats (salt-marshes; Catry et al. 2004) and feeds opportunistically in the channels of the ria's lagoon system. It also feeds in the marine areas close to the colonies and in the salt tanks of lower salinity (Paiva et al. 2008).
Other species observed in this IBA:
Gannet, Great Cormorant, Black-headed Gull, Lesser Black-backed Gull, Yellow-legged Gull, Mediterranean Gull, Little Gull, Little Gull, Caspian Tern, Sandwich Tern, Common Tern, Guillemot and Razorbill.
Conservation responses/actions for key biodiversity
LIFE Project Marine IBAs - LIFE04 NAT/PT/000213
Ria Formosa SPA (PTZPE0017); Decree-law nº 384-B/99 of 23rd September - 67% of the area coincides with the IBA.
Ria Formosa/Castro Marim SCI (PTCON0013); Cabinet Resolution nº 142/97 - 38% of the area coincides with the IBA.
Ria Formosa Nature Park; Decree nº 373/87 of 9th December - 38% of the area coincides with the IBA.
BirdLife International (2020) Important Bird Areas factsheet: Ria Formosa - Oceânica. Downloaded from
http://www.birdlife.org on 08/04/2020.