Alimentación nocturna bajo iluminación artificial de la Gaviota Capucho-Café (Larus Maculipennis) en el muelle de Puerto Madryn (Chubut, Argentina)

Se describe la alimentación nocturna en un ambiente marino de la Gaviota Capucho Café (Larus maculipennis) en noviembre de 2009. Las gaviotas se congregaron durante la noche en el extremo de un muelle de 800 m de extensión en Puerto Madryn (Chubut, Argentina). Las aguas alrededor del extremo del muelle estaban iluminadas por potentes luces que atraían a muchas presas pequeñas a la superficie. Varios cientos de gaviotas, presumiblemente individuos reproductivos provenientes de una colonia cercana, se alimentaron diariamente en este sitio usando diferentes técnicas de alimentación y capturando presas de diferentes especies y tallas. Las presas potenciales fueron capturadas para su identificación a través de muestreos verticales con una red de plancton. Las presas que seguramente capturaron las gaviotas eran Isopoda de tamaño relativamente grande (Idothea sp.), Polychaeta (Platynereis sp.) y larvas de peces (Patagonotothen sp.), así como crustáceos de menor tamaño, mayormente Amphipoda (Phoxocephalidae) y Mysidacea. Las presas pequeñas fueron capturadas mientras las gaviotas nadaban, mediante el picoteo en superficie, mientras que las más grandes fueron capturadas sobrevolando bajo sobre la superficie y a través de zambullidas superficiales. Durante el día, solo unas pocas gaviotas se aventuraron dentro de la bahía, indicando que tomaron ventaja de la oportunidad de alimentación nocturna facilitada por la iluminación artificial. La clara ganancia a corto plazo de la explotación de esta novedosa oportunidad de alimentación podría ser compensada por posibles amenazas tales como una mayor vulnerabilidad a los predadores o la contaminación por derrame de hidrocarburos de los barcos amarrados junto al muelle.This paper describes nocturnal, marine feeding behaviour in the Brown-hooded Gull (Larus maculipennis) in November 2009. The gulls assembled at night at the end of a long pier, running 800 m offshore into the Golfo Nuevo, at Puerto Madryn, Chubut Province, Argentina. Powerful lights predictably lighted the water around the end of the pier and attracted many small prey animals to the surface. Several hundreds of gulls, presumed to be local breeders, came every night to feed on this bounty, using various feeding techniques and taking several prey species and sizes. Potential prey items were caught to be identified by vertical plankton hauls. The gulls most likely took relatively large Isopoda (Idothea sp.), Polychaeta (Platynereis sp.) and fish larvae (Patagonotothen sp.) as well as smaller crustaceans, mostly Amphipoda (Phoxocephalidae) and Mysidacea. The gulls caught small prey items while swimming, by rapid surface pecking, while they hunted the larger prey species by flying low over the water and performing shallow, vertical plunge-dives. During daylight, only few gulls ventured from land into the bay, indicating that they took advantage of the nocturnal feeding opportunity, facilitated by artificial lighting. The clear short-term gain of exploiting this novel foraging opportunity may be offset by potential threats such as increased vulnerability to predators or contamination by oil spills from ships moored along the pier.Fil: Leopold, Mardik F.. Institute for Marine Resources and Ecosystem Studies; Países BajosFil: Philippart, Catharina J.M.. Royal Netherlands Institute for Sea Research; Países BajosFil: Yorio, Pablo Martin. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Nacional Patagónico; Argentina. Wildlife Conservation Society; Estados Unido

Pilot field study: observations from a fixed platform on occurrence and behaviour of common guillemots and other seabirds in offshore wind farm Luchterduinen

Two marine ornithologists spent two days watching seabird behaviour from a fixed platform at the periphery of offshore wind farm Luchterduinen, The Netherlands, in January 2018. The aim of this study was to assess whether meaningful observations could be made from a non-moving platform, that was part of the wind farm scenery, i.e., one of the turbine foundations. On each observation day, a turbine was selected that was located at the wind farm perimeter, that offered views both of the interior of the wind farm and to waters just outside the wind farm. Earlier studies of seabirds in offshore wind farms have shown that many species tend to avoid wind farms, but also that some individuals, of most species, do enter. However, as these studies are typically conducted from moving platforms (ships or aircraft), it is not known how birds behave within a wind farm perimeter. Birds that find themselves between moving turbines might be intimidated. This might impair their normal feeding behaviour at sea, if the birds would be overly watchful, or mainly seeking to exit the wind farm. On the other hand, birds may specifically move into a wind farm, if they can deal with the fact that turbines are present, and if feeding conditions within the wind farm are good. Such birds would be expected to show feeding behaviour, such as diving.Seabirds may also be habituating to the presence of wind farms in their environment. In the airspace below the rotors, at the sea’s surface and under water, there is no danger to seabirds from collision. Seabirds can thus safely enter and feed in offshore wind farms, and may, over the years, have learnt to exploit this new habitat. Therefore, even though earlier studies have shown displacement of seabirds away from offshore wind farms, this may no longer be the status quo as seabirds may be adapting to the new situation: a marine environment with offshore wind farms.Two auk species, the common guillemot and the razorbill, were seen to move through the wind farm. Birds were seen here both flying and swimming, and diving (presumably for food) was commonly seen. Northern gannets were also commonly seen within wind farm perimeters, but only flying: not swimming or diving. We observed bird behaviour during only two days, in a relatively new wind farm not visited by us earlier, while using different methods of observing seabirds, as compared to earlier T-0 and T-1 studies nearby offshore wind farms. Acknowledging these methodological limitations, seabird presence in the wind farm seemed considerably higher than observed during the earlier T-0 and T-1 (personal observations) periods. This might suggest that these birds (both auks and gannets) are habituating to the wind farms in their environment.Based on this pilot study of only two days of observations in only one season, it is fair to conclude that meaningful behavioural observations can be made from the turbine foundations and that the suggested process of habituation can be followed. It is suggested to conduct more such observations and to do so both from peripheral turbines and from turbines deeper into the wind farm

Photo-Identification Methods Reveal Seasonal and Long-Term Site-Fidelity of Risso’s Dolphins (Grampus griseus) in Shallow Waters (Cardigan Bay, Wales)

A photo-identification study on Risso’s dolphins was carried out off Bardsey Island in Wales (July to September, 1997-2007). Their local abundance was estimated using two different analytical techniques: 1) mark-recapture of well-marked dolphins using a “closed-population” model; and 2) a census technique based on the total number of iden-tified individual dolphins sighted over the study period. The mark-recapture estimates of 121 (left sides; 64 - 178, 95% CI; CV 0.24) and 145 dolphins (right sides; 78 - 213, 95% CI; CV 0.24) closely matched the census technique estimates (population size of 90 - 151). It was found that the dolphins showed a degree of long-term and seasonal site-fidelity. A first long-distance match was made for Risso’s dolphins (319 km) between Bardsey Island and Cornwall, confirming they can be wide-ranging animals. This study demonstrates that the combination of systematic and opportunistic photo-ID studies has complementary value as a population assessment tool in generating the first local abundance esti-mate for Risso’s dolphins in UK waters. From the conservation perspective, these studies confirm the regular presence of Risso’s dolphins in these waters and the presence of calves shows breeding. Bardsey Island may be part of a network of localities that are important habitats to this species where it may take advantage of prey abundance in shallow waters. As such, results of this study may provide assistance to include the Risso’s dolphin in future regional conservation strategies including the envisaged marine protected areas

Interactions Between Short-Beaked Common Dolphin (Delphinus delphis) and the Winter Pelagic Pair-Trawl Fishery ff Southwest England (UK)

During offshore and onshore studies (2004 to 2009), the interactions between pair-trawls and short-beaked common dolphins (Delphinus delphis) were studied to better understand the impact of bycatch. A ‘hotspot’ area where pair-trawls overlapped with high dolphin abundance was identified. We made comparisons between boat-based data collected in absence and presence of pair-trawlers. The relative abundance and group-size of dolphins was significantly higher in the presence of pair-trawlers. Dolphins were observed associating with towing and hauling procedures. Significantly, more carcasses occurred in areas with hauling-activity than those without. Body-temperatures obtained from carcasses found near operating pair-trawlers indicated that bycatch mostly occurred at night. During necropsy studies, difficulties were encountered in identifying the fishing-gears responsible. Strandings data highlighted that the number of dead stranded dolphins was probably much higher than previously reported and there was a significant difference in the age and gender-composition of carcasses. Mature/sub-adult males appeared at greater risk from entanglement in pair-trawls offshore, whilst females with young appeared more vulnerable to inshore gillnets. Our findings show that the overlap between pelagic fisheries and the common dolphin hotspot is causing direct mortality through bycatch and, together with recent range-shifts, may have contributed to a localised decline of this species in this winter hotspot since 2007