Diurnal seabird movements at Cabo Carvoeiro (Peniche, Portugal): observations in early October 2012
* Correspondence author: firstname.lastname@example.org
1 Aquatic Biology and Chemistry, Kristianstad University, SE-29188 Kristianstad, Sweden;
2 Hedåkersvägen 29D, SE-21764 Malmö, Sweden;
3 Largo dos Camarnais, no. 3, 2540-479, Pó, Portugal.
The ecology and movements of seabirds are still inadequately understood, mainly because they can rarely be studied efficiently from land. The potential of Cabo Carvoeiro (Peniche, Portugal) for monitoring seabird movements from land is poorly known internationally, as few results from this site have been published in English. Here we present data from standardised counts in October 2012 and draw attention to recent organised seabird counts in Portugal. Despite unfavourable weather conditions for concentrating seabirds towards land, we observed a strong passage of Northern Gannet Morus bassanus, Cory's Shearwater Calonectris diomedea, Great Skua Stercorarius skua, and Balearic Shearwater Puffinus mauretanicus (mean morning passage of 252, 99, 19, and 21 birds / hour, respectively). Manx Shearwater Puffinus puffinus, Sooty Shearwater P. griseus and Great Shearwater P. gravis occurred regularly in low numbers. Extrapolation indicates that thousands of seabirds passed daily within a few kilometres from land. The high counts of some species and the fairly high species diversity observed by us and in the RAM (Rede de observação de Aves e Mamiferos marinhos) initiative show that Cabo Carvoeiro is an outstanding site for monitoring and studying seabirds in the eastern Atlantic, as it is also located further south in the flyway than most other seawatch points. We hope this note will inspire ornithologists from other countries to participate in standardised seabird counts at Cabo Carvoeiro and other Portuguese sites.
The ecology and movements of seabirds remain much less well understood than those of landbirds, mainly because most seabird movements, including their often spectacular migration, cannot be seen from land. Despite recent advances in satellite telemetry and geo-locator technology there is no technique available to monitor seabird migration at sea quantitatively. The scarcity of information about migration movements and numbers makes seabirds vulnerable in an era of global change and fisheries impacting ever more of the marine environment. Indeed, the list of conservation concerns related to seabirds is alarmingly long. In a North Atlantic perspective, it is urgent to gain a better understanding of their movements in time and space. Specifically, on-shore monitoring of sites further south in the East Atlantic seabird flyway would add value by including more species and populations, compared with established count sites further north (e.g. in the UK, Ireland and France). Examining a map of the eastern Atlantic, Cabo Carvoeiro in Portugal promises to provide such information for several reasons (Figure 1). First, central Portugal is within or close to the breeding range of several seabird species occurring in the Mid-Atlantic (Hagemeijer & Blair 1997; Lecoq et al. 2011). Secondly, migrants of these and more northern seabird species pass through the region during migration (e.g. Wernham et al. 2002; Yésou 2003; Meirinho 2009). Thirdly, protruding into the Atlantic as the western most point on the European mainland, Cabo Carvoeiro appears eminently situated for observing passing seabirds that otherwise might not be visible from land. Although known as a seawatching site by Portuguese ornithologists since at least the 1980s, Cabo Carvoeiro remains more or less unknown outside of the country. Its qualities are barely described in ornithological and birding journals alike, and what little has been published in English (and in Portuguese, until recently) provides little detail or is biased towards spectacular days with extremely favourable weather conditions and out-of-the-ordinary totals (e.g. Moore et al. 1997; Moore 2000). The aim of this article is to increase international awareness of the site, by reporting our own results from early October 2012 and by promoting a recent initiative by Portuguese ornithologists (Sengo et al. 2012).
We are grateful to Russell Wynn, Andy Webb, and Martin Heubeck for constructive criticism on this manuscript.
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