Coastal area that stretches from the Paço de Arcos beach in Oeiras, along Cabo Raso and Cabo da Roca and up to Samarra beach, north of Magoito. Part of the IBA overlaps with the marine area of the Sintra-Cascais Site of Community Importance. Naturally, it is an area with a large volume of maritime traffic of various types, as it is located at the entrance to Lisbon harbour. This highly productive IBA has an abundance of sediments and nutrients supplied by the river Tagus and is characterized by its shallow depths, mostly under 100m, a factor which favours the presence of the Balearic Shearwater (Louzao et al. 2006). South of Cascais, the presence of an underwater sewage outlet should be noted, the Guia sewage outlet, where large gatherings of various species of gull and other seabirds are observed. These may be benefiting directly or indirectly from the outflow of waste waters at this location.
Balearic ShearwaterPuffinus mauretanicus: Regular gatherings are observed at this IBA, both during post-breeding dispersal movements and during the winter months (Poot 2005). At the end of the 1980s and the beginning of the 1990s, flocks of around 4,000 birds were regularly recorded (Moore unpublished data,) suggesting a decrease in the effective population in more recent years, coinciding with the decline in the species (Oro et al. 2004, Poot 2005). Mediterranean Gull Laurus melanocephalus: This is the most important location for wintering of this species on the European Atlantic coast and northern Africa (Poot 2006). During the last few years, regular gatherings of several thousand birds have been observed. The origin of these flocks is attributed to the breeding populations in Belgium, The Netherlands and France (Poot 2006). Other species observed in this IBA: Cory's Shearwater, Great Shearwater, Sooty Shearwater, Manx Shearwater, Wilson's Storm-petrel, European Storm-petrel, Leach's Storm-petrel, Gannet, Great Cormorant, European Shag, Common Scoter, Pomarine Skua, Parasitic Skua, Long-tailed Skua, Great Skua, Black-headed Gull, Common Gull, Lesser Black-backed Gull, Yellow-legged Gull, Great Black-backed Gull, Kittiwake, Sandwich Tern, Common Tern, Guillemot, Razorbill and Puffin.
BirdLife International (2020) Important Bird Areas factsheet: Cabo Raso. Downloaded from http://www.birdlife.org on 03/12/2020.