Las colonias de aves marinas de la costa Occidental de Galicia. Características, censo y evolución de sus poblaciones

Bárcena, F. & Souza, J.A. Las colonias de aves marinas de la costa Occidental de Galicia. Características, censo y evolución de sus poblaciones. Ecología 1. (1987). ISSN 0214-0896


 

Henslow’s swimming crab (Polybius henslowii) as an important food for yellow-legged gulls (Larus cachinnans) in NW Spain

Munilla, I. Henslow’s swimming crab (Polybius henslowii) as an important food for yellow-legged gulls (Larus cachinnans) in NW Spain. ICES Journal of Marine Science: Journal du Conseil 54, 631–634 (1997).


An analysis of the contents of 2562 pellets sampled from 1987 to 1993 at breeding colonies and roosting sites showed that Henslow’s swimming crabs (Polybius henslowii) are by far the most important marine prey for yellow-legged gulls (Larus cachinnans) on the coasts of Galicia (north-western Spain), occurring in 36.4% of pellets. The results also suggest that yellow-legged gulls in Galicia are to a great extent marine foragers. Galicia has one of the largest yellow-legged gull populations in western Europe, largely dominating the seabird community. Polybius henslowii is the most abundant decapod crab over the continental shelf of Galicia. It enters coastal waters in large shoals and frequently stays close to the sea surface. Compared with the diets of other yellow-legged gull populations or any of the other closely related gull species, such as the herring (L. argentatus) and the lesser black-backed gull (L. fuscus), Polybius henslowii appears as a characteristic and even exclusive prey of yellow-legged gull populations in the Iberian Atlantic. There is also some evidence that the regular irruption of large Polybius henslowii shoals is a phenomenon peculiar to Iberian Atlantic waters.

Desplazamientos de la Gaviota Patiamarilla (Larus cachinnans) en poblaciones del norte de la Península Ibérica

Munilla, I. Desplazamientos de la Gaviota Patiamarilla (Larus cachinnans) en poblaciones del norte de la Península Ibérica. Ardeola 44, 19–26 (1997).


Se analizan todas las recuperaciones disponibles de gaviotas patiamarillas anilladas como pollos que conciernen al Atlántico norte español (Galicia, Asturias, Cantabria y País Vasco), y se comparan con las recuperaciones de aves anilladas en la provincia de Gerona. Las gaviotas patiamarillas de las colonias del Atlántico norte español no parecen realizar desplazamientos de carácter migratorio, recuperándose la mayoría de las aves a menos de 100 km de la colonia natal, situación que contrasta con el claro comportamiento migratorio de las patiamarillas del Mediterráneo occidental. En las poblaciones del Atlántico se han encontrado diferencias significativas entre clases de edad en las distancias a la colonia natal, correspondiendo los mayores desplazamientos a las aves inmaduras. Por el contrario, los datos de la provincia de Gerona no parecen indicar la existencia de tales diferencias. En ambos casos se observa un marcado ciclo estacional, si bien las menores distancias a la colonia de anillamiento se producen entre mayo y septiembre en el Atlántico, mientras que en Gerona este periodo tiene lugar entre marzo y junio. Por otra parte, los resultados sugieren que las gaviotas del Atlántico norte español constituyen una población cerrada, sin apenas relaciones con otras poblaciones de Larus cachinnans.

Status of the Balearic shearwater (Puffinus mauretanicus) on the Galician coast (NW Iberian Peninsula)

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


This paper aims to assess the status of the threatened Balearic shearwater Puffinus mauretanicus along the Galician coast (NW Iberian Peninsula) by studying its movements and numbers. Balearic shearwaters are detected off Galicia during their annual cycle although they are uncommon between November and May. Overall, 44 groups of over 150 birds have been recorded in seven main areas since 1976, especially in the Vigo Ria and the Pontevedra Ria and along the coast of Bergantiños (Sisargas-Baldaio). Birds have been observed moulting primary and secondary feathers, mainly in June. North-eastward migration is evident along the Atlantic coast (capes Silleiro and Fisterra, daily maximum of 476 birds per hour) between June and August, where it seems to overlap with local movement. However, south-westward migration is far more frequent between September and October (daily maximum of 360 birds per hour) along the Cantabrian coast. The results might be biased due to the methodological problems, on account of the existence of irregular flows, an important inter-annual variability and local movements, probably brought about by the distribution of food resources.

Mass mortality of seabirds in the aftermath of the Prestige oil spill

Munilla, Ignacio, José Manuel Arcos, Daniel Oro, David Álvarez, Patricia M. Leyenda & Alberto Velando. “Mass mortality of seabirds in the aftermath of the Prestige oil spill.” Ecosphere 2, no. 7 (2011): 1-14.


In the winter of 2002–03 the Prestige tanker spilled 60,000 tons of oil over the northern half of the Iberian Coastal Large Marine Ecosystem (northern Portugal to France). Most (c. 85%) of the 22,981 oiled seabirds reported were alcids (i.e., auks): Common Murres (Uria aalge), Razorbills (Alca torda) and Atlantic Puffins (Fratercula arctica). Here we estimated the mortality of alcids in Galicia (northwestern Spain), the area that received most of the Prestige oil and where half of the oiled seabirds were collected. We performed three experiments that included: (1) a test of several drift block models in open sea, to select the one that best fitted the drift of alcid carcasses; (2) the release of 450 drift blocks at 9 offshore points to assess the recovery rate of oiled alcids and its spatial variation; (3) the assessment of beach survey effort and the detectability of drift blocks. Mean mortality estimates and their bootstrapped confidence intervals were obtained through an estimation model that established: (1) a temporal limit of 23 days to block drifting; (2) spatial differences in the recovery rates of blocks depending on how far away from the coast they were released; (3) a correction factor accounting for detectability, and (4) the distribution pattern of the three alcid species involved according to three distance classes, based on ship surveys. The Prestige oil spill, in terms of acute seabird mortality, was one of the worst oil spills ever reported worldwide. Compared to other major oil spills the estimated mortality for the Prestige oil spill was higher than expected from the number of carcasses retrieved. We recommend that drift block assessments of seabird mortality should be included in contingency response plans to oil pollution emergencies; therefore, a supply of drift-blocks designed to mimic the drifting behavior of the marine bird species of interests should be at hand.