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- Seabird abundance and distribution off western iberian waters estimated through aerial surveysPublication . Araújo, Hélder; Rodrigues, Pedro; Bastos Santos, Jorge; Ferreira, Marisa; Pereira, Andreia; Martinez Cedeira, Jose; Vingada, José; Eira, CatarinaWestern Iberian waters are important migratory flyways, stopover sites, and wintering areas for several of the world’s seabird species. To describe seabird species composition, distribution, and abundance in these waters, we performed six aerial surveys in September and/or October of each year, 2010–2015, covering 74 840 km2. Using line transect methodology, 27 396 seabird sightings from 17 taxonomic groups were recorded along 10 496.3 nautical miles (19 433 km). Using the program “Distance,” annual and overall abundance estimates were obtained for nine taxonomic groups: Balearic Shearwater Puffinus mauretanicus, Great Shearwater Ardenna gravis, Cory’s Shearwater Calonectris borealis, shearwaters, Northern Gannet Morus bassanus, Sabine’s Gull Xema sabini, Great Skua Stercorarius skua, storm petrels, and Red Phalarope Phalaropus fulicarius. For the six-year period, Northern Gannet was the most abundant species (89 630 individuals, coefficient of variation [CV] = 6.28%), followed by Cory’s Shearwater (25 044 individuals, CV = 7.56%) and Balearic Shearwater (13 632 individuals, CV = 20.81%). The remaining taxonomic groups exhibited variable abundances. Results confirm that the study area is important to several seabird species, providing baseline estimates to inform conservation policies and instruments, such as the Birds Directive or the Marine Strategy Framework Directive.
- Monitoring Abundance and Distribution of Northern Gannets Morus bassanus in Western Iberian Waters in Autumn by Aerial SurveysPublication . Araújo, Hélder; Rodrigues, Pedro; Bastos-Santos, Jorge; Ferreira, Marisa; Pereira, Andreia; Martínez-Cedeira, José; Vingada, José; Eira, CatarinaSeveral North Atlantic breeding seabirds, such as the Northern Gannet Morus bassanus, use Western Iberian Waters for wintering and migration. In this study, we aimed at producing absolute population estimates of post-breeding Gannets and evaluating the importance of the study area within the species’ migration range. We performed six aerial surveys in September and/or October each year between 2010 and 2015, covering 74,840km2 in total. Using line transect methodology, 3,672 Gannet sightings were recorded along 10,496.3 nautical miles (nm). Immature individuals and adults comprised approximately 87% of all sightings. Using Distance sampling, overall abundance was estimated at 89,930 birds, ranging from 58,010 individuals in 2014 to 128,140 in 2015. the highest densities per sector areas were recorded in the North and Centre sectors whereas the lowest densities were registered in the Galicia sector, the Spanish region within the study area. Gannets were mostly present in shallow shelf waters of the continental shelf, particularly between 3 and 20 nautical miles offshore. Habitat suitability models for Gannets in the study area were tested using several eco-geographical variables and chlorophyll concentrations were found to contribute most to explaining annual Gannet occurrence probabilities. A global interannual spatial analysis demonstrated the core areas for conservation of the Northern Gannet in Western Iberian Waters. Moreover, our results demonstrate that Western Iberian waters are used by almost 10% of the global Northern Gannet population, corroborating the existence of seabird hotspots during the non-breeding period, along migration corridors and at their wintering grounds.