This marine IBA complements the current existing terrestrial IBA (PT014), and stretches to the coastal area of Peniche and cape Carvoeiro. It is a highly productive area as a result of upwelling (Fiúza 1983), supporting the breeding population of Cory's Shearwater on the archipelago almost exclusively, as well as a large number of seabirds on migration and during winter. The extension of the current IBA area southwest was determined by the feeding areas for Cory's Shearwaters, and matches the fishing areas that are locally recognized as important. The Peniche fishing harbour is one of the most important to the fishing industry in Portugal, namely in sardine fisheries. The sea around this archipelago is widely sought out by professional and amateur fishermen, as well as by recreational divers. Given the high number of visitors to the Berlenga island, the tourism induced sea traffic increases exponentially during the summer.
Cory's Shearwater Calonectris diomedea: Its population is estimated at 800 breeding pairs (Lecoq pers. com.), and is regularly monitored. Tagging Cory's Shearwater campaigns using data-loggers confirmed that over 95% of the tagged birds exclusively used this marine area for feeding and resting. Balearic ShearwaterPuffinus mauretanicus: Besides regular and significant records made during the LIFE project, there are several observations of large flocks passing Cape Carvoeiro (Moore, unpublished data). Madeiran Storm-petrel Oceanodroma castro: The only colony on Continental Portugal estimated at 125 breeding pairs (Magalhães 2003) is located on the Farilhões. There are regular records of calls from these birds on Berlenga, but breeding has never been confirmed on this island. Gannet Morus bassanus: The area is used regularly during the winter, and during the autumn and spring migrations. The total wintering population in Portugal is not known. However, observations of flocks numbering several thousands of individuals at various points along the coast are common. The densities observed in this region indicate its importance to the species during winter. Shag Phalacrocorax aristotelis: According to the number of pairs known in the rest of the country (Catry 2002), around 75% of the population of this species breeds on Berlenga, and its colony is estimated at between 79 and 105 pairs (Lecoq 2003 ). Yellow-legged Gull Larus cachinnans: This is the most abundant species on the archipelago, with a population of around 25,000 breeding birds. The number of breeding pairs has increased significantly in the last few decades. As a result, the colony has been subjected to population control measures since 1994, with the aim of stabilizing its population (Amado 2007). Lesser Black-backed Gull Larus fuscus: There is a small breeding population on Berlenga which probably became established in the 1980s (Teixeira 1984) and is estimated at around 30 pairs (Amado 2007). Guillemot Uria aalge: The Guillemot population that breeds on Berlenga is classified as Critically Endangered. The population has dropped drastically from the 6,000 pairs recorded in 1939 (Lockley 1952) to the current residual population of around eight birds (ICNB/RNB 2007). The causes for this decline are attributed to mortality caused by mass fishing, contradicting theories such as global climate change or colony disturbances (Munilla et al. 2007). Other species observed in this IBA: Common Scoter, Great Shearwater, Sooty Shearwater, Manx Shearwater, Wilson's Storm-petrel, European Storm-petrel, Leach's Storm-petrel, Gannet, Great Cormorant, Great Skua, Pomarine Skua, Parasitic Skua, Long-tailed Skua, Common Gull, Great Black-backed Gull, Black-headed Gull, Mediterranean Gull, Kittiwake, Sabine's Gull, Sandwich Tern, Common Tern, Little Tern, Razorbill and Puffin.
BirdLife International (2020) Important Bird Areas factsheet: Berlengas. Downloaded from http://www.birdlife.org on 03/12/2020.