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Movimientos dispersivos de los cormoranes moñudos anillados en las colonias occidentales de Asturias (n=101). Fuente: D. Álvarez (datos propios).
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... Its nesting habitat in Spain includes a wide range of inaccessible sites on the coast, such as cavities, fissures, and cliff ledges. It is generally sedentary, being the individuals faithful to their first breeding area (19,20). It comprises three subspecies: Ph. aristotelis aristotelis, which inhabits the northeast Atlantic coast, from Iceland to the Iberian Peninsula, including Norway and the Kola Peninsula in Russia; Ph. aristotelis riggenbachi, which breeds in the Atlantic coast of Morocco; and finally, Ph. aristotelis desmarestii, which is endemic of the Mediterranean and the Black Sea (21). ...
Sibling species of the Contracaecum rudolphii (s.l.) complex are habitual endoparasites of cormorants of the Phalacrocoracidae family, worldwide. In Europe, the two species, C. rudolphii sp. A and C. rudolphii sp. B, have been identified. However, information regarding the occurrence and distribution of these anisakids in cormorants from Spain is scarce. In the present study, 20 specimens of the European Shag, Ph. aristotelis desmarestii, from the western Mediterranean Spanish marine coast were parasitologically analyzed for the presence of nematodes. All hosts were found parasitized with Contracaecum specimens (n = 1,517). A representative subsample was genetically identified as C. rudolphii sp. A by sequence analysis of the mtDNA cox2 gene and the ITS1 and ITS2 regions of the rDNA. This represents the first report of C. rudolphii sp. A from the Spanish Mediterranean waters. Population genetic analysis was performed including other C. rudolphii sp. A specimens from the west Sardinian and the Tyrrhenian Sea. At the intraspecific level, a significant genetic differentiation (Fst ≈ 0.08, p < 0.00001) between the metapopulation from the Spanish Mediterranean coast and that from the Sardinian waters was observed; whereas, no differentiation was found between metapopulations of the parasite from the Spanish and the Tyrrhenian Italian coast. The findings highly support the hypothesis of the adaptation of the life cycle of C. rudolphii sp. A in brackish and marine ecosystems. Furthermore, the results on the population genetics of C. rudolphii sp. A suggest the possible role of the migration routes of wintering populations of cormorants in the Mediterranean Sea in influencing the parasite genetic structure.
... Se trata de una población que llegó a constituir una de las colonias más importantes de la especie en Europa, llegando a representar el 2% del total de la población mundial de la especie (Velando y Freire, 1999;. Sin embargo, el descenso que ha registrado en los últimos años, ha llevado a considerar que el estado actual de la colonia del Parque Nacional de las Islas Atlánticas se enmarque en la categoría de «en peligro», según los criterios considerados en el Libro Rojo de la Aves de España (IUCN 2001;Velando y Álvarez, 2004). En el último censo realizado en 2017 se registraron 255 parejas (Munilla, 2017). ...
... El arrastre, que consiste en una red que barre el fondo del mar, capturando todo lo que encuentra a su paso, está prohibido en las aguas del entorno de las Islas Cíes, ya que es el sistema de pesca industrial más invasivo y que más descartes genera, debido a su escasa selectividad. Sin embargo, también hay que mencionar que las artes de pesca artesanal mal gestionadas pueden generar importantes impactos en los entonos naturales (Mouriño et al., 2004;Velando y Álvarez, 2004). ...
... 1761), es un ave marina que habita en zonas acantiladas del sur de Europa y norte de África. Está catalogada como "Vulnerable" en el Libro Rojo de las Aves de España (Velando y Álvarez, 2004) y se encuentra en el Anexo I de la Directiva de Aves. ...
En 2003 se inició en las islas Baleares un programa de anillamiento de la subespecie mediterránea de cormorán moñudo con anillas de lectura a distancia. En 2014 el programa se amplió a Cataluña y en 2015 a la Región de Murcia. Desde entonces se han anillado 599 individuos y se han obtenido 2.408 lecturas de 194 ejemplares. La mayoría de las lecturas se producen cerca del lugar de anillamiento confirmando el carácter sedentario de la especie. Sin embargo, también se detectan movimientos más largos con varios ejemplares marcados en islas Baleares que cruzan a la costa peninsular y que podrían estar contribuyendo al proceso de colonización que se observa durante los últimos años en Cataluña y la Región de Murcia.
... As described above, a site was considered occupied if a nest was built or if any evidence of reproduction (eggs or chicks) was recorded. The reproductive success of each occupied site was estimated as the number of chicks surviving to full growth,[35 days of age (Barros et al. 2013). We also compared the reproductive success in our study area with the reproductive success in two nearby freemink islands (see ESM). ...
... Additionally, the activity of predators in colonies may influence adult or juvenile dispersal (Oro et al. 1999). In our study area, adult shags are characterized by high site fidelity (Velando and Freire 2002;Barros et al. 2013). During our study, of 78 adult shags ringed after mink arrival and resighted anywhere, only one moved to another colony, so adult dispersal is not likely to be responsible for the observed patterns. ...
Non-native invasive species are one of the most serious threats to biodiversity and are considered the leading cause of extinction of several bird taxa, including seabirds. Introduced American mink (Neovison vison) have caused devastating effects on island populations of several colonial seabird species. In this study, we investigated the direct and indirect effects of mink on population dynamics and reproductive success of European shags (Phalacrocorax aristotelis) breeding at Illas Cíes, one of the most important colonies of the species in Southern Europe. A severe episode of mink predation on adult shags occurred in the year when mink arrived in the breeding colonies, though the number of shags killed dropped abruptly in subsequent years. We found that, after the arrival of mink, shags moved to nest-sites that afforded greater protection from carnivores. This shift caused a substantial reduction in mortality by predation, but probably entailed a cost in terms of their reproductive success because sites with lower levels of predation risk showed a higher risk of egg loss by nest flooding due to poorer drainage. Our study highlights that behavioural plasticity may allow shags to cope with invasive predators.
... A previous European scale study of the population genetic structure of the species identified a genetic cluster at the southern limit (including the R ıas Baixas population; Barlow et al. 2011), reflecting limited levels of contemporary gene flow due geographic constraints. Preliminary analysis of dispersal patterns also suggested that breeding shags in the R ıas Baixas population are currently isolated from other populations (Velando & Alvarez 2004). This coastal seabird is a year-round local resident in the study area (Velando & Munilla 2008) and is highly philopatric, with most of the birds recruiting within 5 km of their natal site (Velando & Freire 2002; Barros et al. 2013 ). ...
... In addition to direct mortality, longterm consequences have been attributed to stressful conditions after the oil spill, including delayed effects in response to sublethal oil exposure and reduced food availability (Velando et al. 2005aVelando et al. , 2010 Velando & Munilla 2008 ). Prior to the Prestige oil spill, the population was declining at an annual rate of 5% (Velando & Freire 2002), and it was classified as 'endangered' in the Red Book of Birds of Spain (Velando & Alvarez 2004). Five years after the Prestige oil spill, the breeding population of the shag population in the R ıas Baixas was about 70% lower than prespill counts ( Alvarez & Velando 2007, seeFig. ...
... This study was carried out in the breeding colonies of the European shag in the R ıas Baixas (Galicia, Spain) between 2004 and 2013. This area holds the largest population (80% of the total) of European shags in the Atlantic Iberian Peninsula (Velando & Alvarez 2004). Breeding colonies are found in the Illas Atl anticas National Park, including three groups of islands (Illas C ıes, Illa de Ons and Sagres; seeFig. 1 in Barros et al. 2013). ...
Loss of genetic diversity is thought to lead to increased risk of extinction in endangered populations due to decreasing fitness of homozygous individuals. Here, we evaluated the presence of inbreeding depression in a long-lived seabird, the European shag (Phalacrocorax aristotelis), after a severe decline in population size by nearly 70%. During three reproductive seasons, 85 breeders were captured and genotyped at seven microsatellite loci. Nest sites were monitored during the breeding season to estimate reproductive success as the number of chicks surviving to full size-grown per nest. Captured birds were tagged with a ring with an individual code, and resighting data was collected during seven-year period. We found a strong effect of multilocus heterozygosity on female reproductive performance, and a significant, although weaker, effect on breeder survival. However, our matrix population model suggests that this relatively small effect of genetic diversity on breeder survival may have a profound effect on fitness. This highlights the importance of integrating life-history consequences in HFC studies. Importantly, heterozygosity was correlated across loci, suggesting that genome-wide effects, rather than single loci, are responsible for the observed HFCs. Overall, the HFCs are a worrying symptom of genetic erosion in this declining population. Many long-lived species are prone to extinction, and future studies should evaluate the magnitude of fitness impact of genetic deterioration on key population parameters, such as survival of breeders.This article is protected by copyright. All rights reserved.
... In this study, we analyzed the interaction between recreational boating and a near shore marine bird, the European Shag (Phalacrocorax aristotelis), in the MPA around the Cíes archipelago, which is part of the National Park of the Atlantic islands of Galicia (northwestern Spain). This protected area holds about two thirds of the European shags breeding in Atlantic Iberia, a population that is under the risk of extinction (Velando and Alvarez, 2004). This threatened population has been declining at a rate of about À12% a year in the last 10–15 years, due to the 2002 Prestige oil spill and to continued low survival and reproductive success (Velando and Freire, 2002; Velando and Munilla, 2008). ...
The provision of recreational opportunities is one of the important human goals of marine protected areas. However, as levels of recreational use increase, human disturbance is likely to cause significant detrimental effects upon wildlife. Here we evaluate the best managing options to mitigate the impact of sea-based tourism on the foraging activity of an endangered population of European shags, Phalacrocorax aristotelis, in a coastal marine protected area (Cíes islands, north-western Iberia). Boat disturbance elicited a characteristic avoidance behavior that resulted in a substantial reduction in foraging activity as levels of boat use increased. Moreover, boats excluded shags from the best feeding areas, resulting in higher densities of foragers in areas of little boat traffic. We used a behavioral model to explore the effects of managing strategies aimed at reducing the impact of boats on the foraging activity of shags. Our model suggested that in low boat disturbance scenarios limiting the number of boats using the reserve would be a better management option than habitat protection (i.e. the establishment of set-aside areas free of boat traffic). On the contrary, when boat disturbance levels are high the protection of habitat is recommendable, even if spatial variation in habitat quality is unknown or poorly assessed. Our study stresses the point that management strategies to minimize disturbance to foraging seabirds may depend on the spatial overlap between sea-based recreational activities and foraging seabirds and the spatial variation in marine habitat quality for seabirds.
... 2000 pairs), which is resident in the area the whole year round. Secondly, most of them (85%) are concentrated in just two breeding colonies, in the Illas Cíes and Illas Ons (Parque Nacional de Illas Atlánticas, see Fig. 1); this distribution makes these populations highly sensitive to any environmental hazard, such as oil spills (Velando and Alvarez, 2004). Finally, the Galician shag populations were reported to be slightly declining prior to the oil spill (Velando and Freire, 2002) and a 50% decrease in breeding success was observed for the oiled colonies of Illas Cíes and Ons during the 2003 breeding season (Velando et al., 2005). ...
The Prestige oil spill resulted in the mortality of several seabird species on the Atlantic NW coast of Spain. Shag casualties were particularly relevant, since populations are resident in the area the whole year round and because of several features which make them highly vulnerable to environmental hazards. Ecological catastrophes give us the opportunity of collecting samples which, otherwise, would be difficult to obtain. We examine the potential of shag corpses as bioindicators of inorganic pollution and the possible factors of variability, such as biological traits (sex, age) or nutrition status. We determined trace elements (Hg, Se, Cr, Pb, Zn and Cu) and isotopic signatures (15N, 13C) in soft tissues (muscle, liver) and in primary feathers formed at different times (before and after the Prestige) in individuals of known sex and age, collected at the time of the Prestige disaster. These were compared with data from another group of shags trapped accidentally in fishing gear in 2005. Our results did not seem to be affected by sex or age on any of the analysed variables. The higher nitrogen isotopic signatures in the soft tissues of the Prestige shags may be related to the nutrition stress caused by a poorer body condition, which is also reflected in increasing levels of some metals in the liver. This isotopic enrichment was also observed in newly forming feathers when compared to the old ones. On the other hand, the lower delta15N and Hg values in shag feathers from 2005 point to a shift in feeding resources to prey of lower trophic levels. We found that feather features (being an inert tissue and having a conservative composition), if combined with careful dating and chemical analysis, offer a very useful tool to evaluate temporal and spatial changes in seabird ecology in relation to pollution events.
Environmental drivers, including anthropogenic impacts, affect vital rates of organisms. Nevertheless, the influence of these drivers may depend on the physical features of the habitat and how they affect life history strategies depending on individual covariates such as age and sex. Here, the long-term monitoring (1994-2014) of marked European shags in eight colonies in two regions with different ecological features, such as foraging habitat, allowed us to test several biological hypotheses about how survival changes by age and sex in each region by means of multi-event capture-recapture modelling. Impacts included fishing practices and bycatch, invasive introduced carnivores and the severe Prestige oil spill. Adult survival was constant but, unexpectedly, it was different between sexes. This difference was opposite in each region. The impact of the oil spill on survival was important only for adults (especially for females) in one region and lasted a single year. Juvenile survival was time-dependent but this variability was not synchronized between regions, suggesting a strong signal of regional environmental variability. Mortality due to bycatch was also different between sex, age and region. Interestingly the results showed that the size of the fishing fleet is not necessarily a good proxy for assessing the impact of bycatch mortality, which may be more dependent on the fishing grounds and the fishing gears employed in each season of the year. Anthropogenic impacts affected survival differently by age and sex, which was expected for a long-lived organism with sexual size dimorphism. Strikingly, these differences varied depending on the region, indicating that habitat heterogeneity is demographically important to how environmental variability (including anthropogenic impacts) and resilience influence population dynamics. This article is protected by copyright. All rights reserved.
The Mediterranean shag (Phalacrocorax aristotelis desmarestii) and the great cormorant (P. carbo sinensis) are syntopic birds in an area encompassing Grosa Island and the Mar Menor coastal lagoon (SE Spain, western Mediterranean) during the breeding season of the former and the wintering period of the latter. Diet composition of both birds was studied through pellet analysis and otolith identification. Competition for fish resources between these two seabirds and with local artisanal fisheries was assessed. Shags preyed preferentially on small pelagic fish, and great cormorants mainly consumed demersal fish. Shag diet consisted of marine fish strictly, but great cormorant fed in all the available environments in the study area, including marine, transitional (coastal lagoon) and freshwater reservoirs. The great dissimilarity observed between shag and great cormorant diet composition showed no competition between them. The low shag population density and fishing effort in their foraging area suggested no competition with fisheries. Conversely, great cormorant population density in the study area was very high, and they foraged on fish of high commercial value. However, competition between great cormorant and artisanal fisheries only affected some of the less abundant species fished.
In this study, we analysed the viability of seabird populations, specifically the European shag, after the invasion of the American mink. In the last decade the shags at Cíes islands, the southernmost archipelago of the Park, experienced a population collapse in parallel with a similar reduction in its level of heterozygosity. Data from marked individuals suggest that the loss of genetic diversity leaded to a decline in survival and reproduction. In Cíes, an important episode of mink predation on adult shags occurred in the year when mink arrived in breeding colonies, though the number of shags killed dropped abruptly in subsequent years. We found that, after the arrival of mink, shags nested on sites where the risk of predation by mink was low, probably to avoid
predators. Nevertheless, mink presence had negative effects on shag reproduction and population growth. Our results indicated that the effects of mink should be integrated in a population dynamics framework together with other threats operating, such as the long‐lasting effects of the Prestige oil spill. We have also analysed the presence of mink in the National Park (islands of Cies and Sálvora). In total, 87 minks were captured during
2005‐2013, and currently, mink are virtually eradicated from the Park. The genetic analysis of mink populations in both the Park and the nearby coast suggested that minks colonised the islands in a few or a single event that probably originated from fur‐farm releases rather than migrants from feral populations. Overall, our results suggest that the phenotypic plasticity of shags and the success of mink eradication campaigns could have mitigated the effects of mink presence on European shags at Cíes. Nonetheless, this population shows worrying symptoms of concern, which may affect its future persistence.
