Diurnal seabird movements at Cabo Carvoeiro (Peniche, Portugal): observations in early October 2012

Johan Elmberg1*, Erik Hirschfeld2 and Helder Cardoso3

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.

Full paper

Abstract

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.

Introduction

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).

Acknowledgements

We are grateful to Russell Wynn, Andy Webb, and Martin Heubeck for constructive criticism on this manuscript.

References

Granadeiro, J. P., Alonso, H., Almada, V., Menezes, D., Phillips, R. A. & Catry, P. 2009. . Mysterious attendance cycles in Cory's shearwater, Calonectris diomedea: an exploration of patterns and hypotheses. Animal Behaviour 78: 1455-1462.

Guilford, T., Wynn, R., McMinn, M., Rodriguez, A., Fayat, A., Maurice, L., Jones, A. & Meier, R. 2012. Geolocators reveal migration and pre-breeding behaviour of the critically endangered Balearic Shearwater Puffinus mauretanicus. PLoS ONE 7(3): e33753.

Hagemeijer, E. J. M. & Blair, M. J. (eds.) 1997. The EBCC Atlas of European Breeding Birds: Their Distribution and Abundance. Poyser, London.

Lecoq, M., Ramirez, I., Geraldes, P. & Andrade, J. 2011. First complete census of Cory's Shearwaters Calonectris diomedea borealis breeding at Berlengas Islands (Portugal), including the small islets of the archipelago. Airo 21: 31-34.

Meirinho, A. I. G. 2009. Distribução de Alcatraz (Morus bassanus) na costa continental portuguesa e sua relação com variáveis ambientais. Masters Thesis, Universidade Nova de Lisboa, Lisbon.

Moore, C. C. 2000. Movimentações invulgares de aves marinhas junto ao Cabo Carvoeiro, Outono de 1999 - uma discussão. Pardela 13: 7-10.

Moore, C., Elias, G. & Costa, H. 1997. Seawatching off Portugal. Birding World 10: 433-434.

Mouriño, J., Arcos, F., Salvadores, R., Sandoval, A. & Vidal, C. 2003. Status of the Balearic shearwater (Puffinus mauretanicus) on the Galician coast (NW Iberian Peninsula). Scientia Marina 67(suppl. 2): 135-142.

Paiva, V. H., Guilford, T., Meade, J., Geraldes, P., Ramos, J. A. & Garthe, S. 2010. Flight dynamics of Cory's shearwater foraging in a coastal environment. Zoology 113: 47-56.

Poot, M. 2005. Large numbers of staging Balearic Shearwaters Puffinus mauretanicus along the Lisbon coast, Portugal, during the post-breeding period, June 2004 Airo 15: 43-50. .

Sengo, R., Oliveira, N., Andrade, J., Barros, N. & Ramirez, I. 2012. Três anos de RAM em Portugal Continental (2009-2011). Sociedade Portuguesa para o Estudo das Aves, Lisbon.

Walker, F. J. 1996. Observations of movements of North Atlantic Gannets Morus bassanus from Cape St Vincent, Portugal.Seabird 18: 44-48.

Wernham, C. V., Toms, M. P., Marchant, J. H., Clark, J. A., Siriwardena, G. M. & Baillie, S. R. (eds.) 2002. The Migration Atlas: movements of the birds of Britain and Ireland. Poyser, London

Yésou, P. 2003. Recent changes in the summer distribution of the Balearic shearwater Puffinus mauretanicus off western France. Scientia Marina 67(suppl. 2): 143-148.