Soil eutrophication in seabird colonies affects cell wall composition: Implications for the conservation of rare plant species

Otero, X.L., Fernández-Balado, C., Ferreira, T.O., Pérez-Alberti, A. and Revilla, G., 2021. Soil eutrophication in seabird colonies affects cell wall composition: Implications for the conservation of rare plant species. Marine Pollution Bulletin, 168, p.112469.

Seabird colonies exert a strong influence on coastal ecosystems, increasing soil nitrogen bioavailability and modifying plant communities. Previous studies have evidenced that increased N in soils leads to changes in plant cell wall composition; however, this effect has not been assessed in seabird colonies. The main objective of this study was to determine the influence of seabird colonies on nitrogen, cellulose and lignin content in cell walls. For this purpose, analyses were performed on droppings, soils and three native plant species (Armeria pubigera, Armeria pungens and Corema album) growing in yellow-legged gull colonies. The results showed that N excreted by yellow-legged gull is assimilated by plants, increases N content in plant tissues and reduces cellulose and lignin synthesis, therefore potentially altering plant resistance against phytoparasites.


Influence of fisheries on the spatio-temporal feeding ecology of gulls along the western Iberian coast

Calado, J.G., Veríssimo, S.N., Paiva, V.H., Ramos, R., Vaz, P.T., Matos, D., Pereira, J., Lopes, C., Oliveira, N., Quaresma, A. and Ceia, F.R., 2021. Influence of fisheries on the spatio-temporal feeding ecology of gulls along the western Iberian coast. Marine Ecology Progress Series, 661, pp.187-201

Gulls are highly opportunistic seabirds, and the exploitation of fishery discards has led to many population increases worldwide. We investigated the importance of fish in the diet of yellow-legged Larus michahellis and Audouin’s gulls L. audouinii and assessed the influence of fishery discards on their feeding ecology. We collected pellets from 4 islands along the western Iberian coast during pre-breeding, breeding, and post-breeding seasons from 2014 to 2018. Stable isotopes (from adult blood, and chick and adult feathers) were used to investigate spatial, seasonal, and inter-annual differences in their feeding ecology. We used pellet, stable isotope (δ15N, δ13C, and δ34S), and biochemical (triglycerides, uric acid, total protein, and carotenoids in adult plasma) analyses to investigate their relationships with fish landings across the annual cycle. Results revealed that the fish species consumed by gulls matched those landed by local fisheries on all study islands, and there was a positive association of pelagic and demersal fish diets with fish landing quantities for 2 islands. δ34S values suggest different self-feeding and chick-provisioning strategies in relation to fisheries. δ15N values exhibited strong negative correlations with fish landings, and triglycerides were positively correlated with pelagic but not with demersal fish landing quantities, suggesting that gulls fed more on lower trophic level and higher energetic content pelagic fish than on demersal fish. Overall, our results based on several techniques suggest that gull feeding ecology was linked to fishery discards, which in view of the new EU landing obligation may have major implications for both gull populations across Europe.

Seabird colonies as the main source of nutrients for the coastal ecosystems in the Atlantic Islands of Galicia National Park (NW Spain)

De La Peña-Lastra, S., Pérez-Alberti, A. and Otero, X.L., 2021. Seabird colonies as the main source of nutrients for the coastal ecosystems in the Atlantic Islands of Galicia National Park (NW Spain). Chemosphere, 275, p.130077.

Seabirds form large colonies during the reproductive period, producing substantial changes in coastal ecosystems. The present study quantifies the amount of N and P deposited in colonies of yellow-legged gull (Larus michahellis) in the Atlantic Islands of Galicia National Park (AINP). Based on the composition of droppings, the amount of total N (TN), total P (TP) and bioavailable P (Pbio) deposited directly on the area occupied by the colony was determined. In addition, the amount of NH3 released into the atmosphere was also estimated by applying a bioenergetic model. The results indicated that 5.35 t total N, 3.35 t total P and 1.24 t bioavailable P are deposited in the colony annually. The archipelagos that received the greatest amount of nutrients were the Cíes Islands (2.37 t TN y−1, 1.48 t TP y−1, 0.55 t Pbio y−1), Sálvora (1.94 t TN y−1, 1.22 t TP y−1, 0.55 t Pbio y−1) and Ons (1.04 t TN y−1, 0.65 TP y−1, 0.24 t Pbio y−1). Rainwater from the colonies showed higher values of nutrients than in the control plot, possibly also due to gull influence. Therefore, the yellow-legged gull colony seems to be the most important source of nutrients at a local level, exerting a clear influence on the N and P cycles in this National Park. Another aspect worth taking into consideration is that increased N and P bioavailability may have a negative effect on the conservation of rare or threatened habitats and species by promoting the expansion of non-native ruderal species.

The importance of marine resources in the diet of urban gulls.

de Faria, J.P., Vaz, P.T., Lopes, C.S., Calado, J.G., Pereira, J.M., Veríssimo, S.N., Paiva, V.H., Gonçalves, A.M. and Ramos, J.A., 2021. The importance of marine resources in the diet of urban gulls. Marine Ecology Progress Series, 660, pp.189-201.

The availability of anthropogenic food subsidies has promoted an increase in generalist opportunistic gull species, which currently breed and forage on predictable anthropogenic resources (e.g. landfills). Here we investigated whether marine resources are still important to urban-dwelling gulls. We studied 4 natural and 2 urban yellow-legged gull Larus michahellis colonies and compared (1) diet composition (through pellet analysis) and (2) isotopic niches of adults and chicks, (3) diet delivered to chicks of different ages, and (4) fatty acid (FA) composition of fledglings, in order to assess diet composition, diversity and quality, and the relevance of marine prey for natural and urban gull populations. Adult urban gulls consumed considerably lower proportions of marine prey when compared to gulls from natural colonies; however, they fed their younger chicks (<20 d old) mostly with fish, representing 61-80% of their chick food deliveries. Refuse items were mostly delivered to chicks older than 20 d. Overall, urban isotopic niches were not completely distinct from those of natural colonies, in some cases sharing ca. 50% of their niche space. Fledglings from the most urbanized colony presented overall higher FA concentrations and diversity, but they were lacking some omega-3 FAs relevant to their physiology. Our results highlight the importance of marine resources in the diet of urban gulls, particularly during early chick rearing, the relevance of food sources in the area around the breeding colonies and the fact that urban gulls benefit from year-round reliable anthropogenic food resources

Levels of Zinc, Cadmium, and Lead in liver, kidney, and feathers of Atlantic Puffins (Fratercula arctica) from Spain.

Barrales, I., Hernández-Moreno, D., Fidalgo, L.E., López-Beceiro, A., Martínez-Morcillo, S., Sánchez-Montero, L., Prado Míguez, M., Soler, F. e Pérez-López, M., (2021). Levels of Zinc, Cadmium, and Lead in liver, kidney, and feathers of Atlantic Puffins (Fratercula arctica) from Spain. Toxicological & Environmental Chemistry, pp.1-24.

Zinc, cadmium, and lead in livers, kidneys, and feathers of 48 young and adult Atlantic puffins found dead or dying off the coast of Galicia (Northwest Spain) were determined. The most abundant between the three elements was the essential metal zinc, with highest mean levels (173±9mg/kg dry weight) in livers. For the two non-essential metals, the highest mean levels of cadmium were found in kidneys (22.1 ± 1.0 mg/kg dry weight), and of lead in feathers (1.31±0.10mg/kg dry weight). For some birds, concentrations of zinc and cadmium exceeded established risk levels. The concentrations of the three metals were positively cor- related in livers. In kidneys and livers, cadmium levels were correlated. With respect to age, the levels of the three metals in adults were higher than in young animals. Female birds showed significantly higher levels than males. The results are useful for establishing baseline data of the concentrations of the three metals for this species.

Effects of a yellow legged gull (Larus michahellis) colony on soils and cliff vegetation in the Atlantic Islands of Galicia National Park (NW Spain)

De La Peña-Lastra, S., Gómez-Rodríguez, C., Pérez-Alberti, A., Torre, F. and Otero, X.L., 2021. Effects of a yellow legged gull (Larus michahellis) colony on soils and cliff vegetation in the Atlantic Islands of Galicia National Park (NW Spain). Catena, 199, p.105-115.

Seabirds are powerful environmental modulators, generating major changes in soil properties and vegetation in areas where their breeding colonies are established. One of the largest yellow-legged gull colonies in the world is found in the Atlantic Islands of Galicia National Park. In this study, we performed seasonal monitoring, over a period of 5 years, of the flora and soil in eight subcolonies characterized by different densities of gulls. Soil nutrient concentrations differed significantly between the control site and the subcolonies, as well as between seasons; the concentrations of N-NO3 and bioavailable P were highest in samples obtained at the end of the breeding season. Principal Component Analysis (PCA) transformed the environmental variables into three main components following varimax rotation. The PCA components were used as potential predictors in distance-based Redundancy Analyses (db- RDA) to explain turnover and also nestedness patterns in plant assemblages. Species turnover was explained by both natural (salinity) and nutrient gradients, while none of the relationships were significant in the nestedness analysis. Floristics inventories clearly revealed ruderalization of vegetation in the densest subcolonies, which led to total replacement of the most representative vascular plant species by eutrophic and ruderal species. PERMANOVA analysis showed that seagull density in 1991, when the seagull population was at its highest, could be used to group similar plant assemblages; however, this relationship was not observed for seagull density in 2011, which was 70–90% lower than in 1991. The study findings indicate that the environmental effects of seabird colonies are long lasting and that disappearance of the birds does not lead to restoration of the previous vegetation. The gull colony has irreversibly transformed the soil and vegetation of cliffs, generating a new environmental system.

Soil under dead or live organic matter systems: Effect of: European shag (Phalacrocorax aristotelis L.) nesting on soil nematodes and nutrient mineralization

Here we studied whether soil systems differ if they are under the influence of live (plants) or dead organic matter systems (nest) in terms of C and N mineralization, microbiological characteristics and nematode trophic group structure. We analyzed physicochemical and microbiological properties of soils inside and outside nests of the European shag (Phalacrocorax aristotelis L.) on the Cíes Islands (NW Spain). We sampled fresh soil below dead (nests) and live organic matter (plants) (paired samples, n = 7). Soil of nests had lower organic matter and higher electric conductivity and dissolved organic C and extractable N contents than the soil of plants. Microbial biomass and activity were greater in soil of nests than in soil of plants. The abundance of nematode trophic groups (bacterivores, fungivores, omnivores and herbivores) differred between soils of nests and plants, and the soil of plants supported a more abundant and diverse nematode community. The present results points to that source of organic matter promote differences in the decomposer community, being more efficient in soil of nests because C mineralization is greater. Further, this occurred independently of the complexity of the systems, higher in the soil of plants with more groups of nematodes.

Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development

Noguera, J.C., da Silva, A. and Velando, A., Egg corticosterone can stimulate telomerase activity and promote longer telomeres during embryo development. Molecular Ecology.

It is often assumed that the transfer of maternal glucocorticoids (GCs; e.g. corticosterone or cortisol) to offspring is an inevitable cost associated with adverse or stressful conditions experienced by mothers. However, recent evidence indicates that maternal GCs may adaptively program particular physiological and molecular pathways during development to enhance offspring fitness. In this context, an important mechanism through which maternal GCs may lastingly affect offspring phenotypic quality and survival is via effects on embryo telomerase activity and so on offspring postnatal telomere length. Here, using a field experimental design for which we manipulated the corticosterone content in yellow‐legged gull (Larus michahellis) eggs, we show that embryos from corticosterone‐injected eggs not only had a higher telomerase activity but also longer telomeres just after hatching. A complementary analysis further revealed that gull hatchlings with longer telomeres had a higher survival probability during the period when most of the chick mortality occurs. Given the important role that telomere length and its restoring mechanisms have on ageing trajectories and disease risk, our findings provide a new mechanistic link by which mothers may presumably shape offspring life‐history trajectories and phenotype.

El cormorán moñudo en Galicia. Población reproductora en 2017 y método de censo.

Munilla, I.; Barros, A. 2018. El cormorán moñudo en Galicia. En, J. C. del Moral y N. Oliveira (Eds.): El cormorán moñudo en la península ibérica. Población reproductora en 2017 y método de censo, pp. 41. SEO/BirdLife. Madrid.

Se localizaron 1.408 parejas distribuidas en 58 lugares de cría, 50 de ellos con dos o más parejas. Las colonias se distribuyen a lo largo del litoral gallego al norte de Fisterra y en los archipiélagos exteriores de las Rías Baixas (Cíes, Ons y Sálvora). Cerca del 70% de la población se concentra en las Rías Baixas, donde crían 950 parejas en 7 islas, entre ellas Ons (571 parejas), San Martiño (Cíes, 100 parejas) y Monteagudo (Cíes, 99 parejas), que son los núcleos de reproducción más nutridos de la península. En el resto de la costa la mitad de la población se reparte por el tramo comprendido entre las islas Sisargas y cabo Prior, cuyas principales colonias son Cabo de Mera (70 parejas) y Gabeiras de Doniños (39 parejas). En la costa de Lugo el principal núcleo de cría es la isla de Ansarón (34 parejas). La población de Galicia representa el 74,6% de la población nidificante en la España peninsular y el 80,0% de los efectivos de la subespecie aristotelis en la península ibérica.

Censo das poboacións reproductoras de corvo mariño, gaivota patiamarela, gaivota escura e gaivotón, e seguimento remoto de corvos mariños no Parque Nacional Marítimo e Terrestre das illas Atlánticas de Galicia en 2019

Munilla, I. e Lapeña, F. 2019. Censo das poboacións reproductoras de corvo mariño, gaivota patiamarela, gaivota escura e gaivotón e seguimento remoto de corvos mariños no Parque Nacional Marítimo e Terrestre das illas Atlánticas de Galicia en 2019. Parque Nacional Marítimo e Terrestre das Illas Atlánticas de Galicia. Outubro 2019.


Corvo mariño (P. aristotelis)

  • A poboación reprodutora de corvo mariño no Parque Nacional en 2019 estimouse en 962 parellas repartidas en oito colonias principais. Esta poboación representa o 68% do censo galego da especie.
  • O 64% da poboación amoreouse no arquipélago de Ons, o 31% no arquipélago de Cíes e o 7% restante en Sagres. A colonia máis numerosa é Ons Norte con 581 parellas, máis da metade das estimadas para o conxunto do Parque.
  • O número de parellas censadas supón un lixeiro ascenso (69 parellas, 7,6%) con respecto dos datos de 2018.
  • Compre destacar a pequena colonia localizada en Noro (arquipélago de Sálvora) xa que esta localidade fora abandonada hai anos trala entrada do visón americano.
  • A estima do éxito reprodutor no Parque Nacional en 2019 foi de (media ± desviación típica): 0,81 ± 1,10 polos por niño (N = 73 niños), con diferenzas marcadas entre os tres arquipélagos: Cíes = 0,64 ± 1,13 polos por niño; Ons = 0,86 ± 1,15; Sagres = 0,93 ± 1,05. Un ano máis Cíes é a colonia co menor suceso.

Gaivota patiamarela (L. michahellis)

  • A poboación reprodutora de gaivota de patas amarelas no Parque Nacional en 2019 estimouse en 9173 parellas repartidas en 11 colonias principais localizadas nos catro arquipélagos do Parque. As colonias desta especie ocupan a práctica totalidade da superficie insular do Parque libre de arboredo e distribúese por tódolos illotes do Parque con vexetación herbácea.
  • Perto da metade da poboación concéntrase no arquipélago de Sálvora (4284 parellas; 46,7%), un tercio (3134 parellas; 34,2%) nas illas Cíes e o 19% restante nas illas de Ons (1743 parellas). No arquipélago de Cortegada existe unha pequena colonia de 12 parellas no illote de Briñas.
  • En comparación cos datos de 2015, ano do último censo, perdéronse un total de 1622 parellas reprodutoras (-15,0%). O arquipélago co maior desplome foi Ons (-22,3%), seguido de Sálvora (-14,9%) e Cíes (-11,0%).
  • A comparación cos datos de 2006, o ano co maior rexistro da serie de censos, amosa unha perda de 21.275 parellas, o 70% da poboación reprodutora. A taxa de declive anual equivalente foi logo do -8,8%. Existen diferenzas acusadas entre os padróns de cambio poboacional rexistrados nos tres arquipélagos ao longo da serie de censos ao dispor (1976-2019).
  • O seguimento interanual do número de territorios aparentemente ocupados nos sectores de censo repartidos polas colonias do Parque indica unha diminución da poboación reprodutora de gaivota patiamarela do 7% en relación ás cifras de 2018. O cambio foi moi heteroxéneo espacialmente, con aumentos nos sectores de O Faro e Sálvora, e caídas mesmo fortes no resto.
  • O éxito reprodutor na parcela de seguimento da illa de O Faro (Cortello do Porco) foi baixo (media ± desviación típica = 0,56 ± 0,78 polos a voar por territorio), inferior ao estimado en 2018.

Gaivota de asa escura (L. fuscus)

  • En 2019 a poboación reprodutora de Larus fuscus no Parque foi estimada en 28 parellas, catro por cima das estimadas en 2018.
  • Entre 2011 e 2019 a perda de poboación ten sido do 36,0%, equivalente ao -5,3% anual.

Gaivotón (L. marinus)

  • A estima da poboación reprodutora de gaivotón no ano 2019 é de dúas parellas unha na illa Vionta e máis a outra en Sálvora. A parella de Sálvora quitou dous polos.

Seguimento remoto de corvo mariño con transmisores GPS/GSM

  • Este ano equipáronse dous corvos mariños con equipos de seguimento remoto GPS/GSM, os dous na illa do Faro, un na subcolonia da Furna do Inferno e outro na do Estripeiral. Dos dous exemplares equipados en 2018 un deles continua a dar sinal normalmente. En conxunto rexistráronse 9462 localizacións entre xaneiro e setembro de 2019.
  • O corvo de Sagres desenvolveu a súa actividade nunha área moi reducida (polígono mínimo convexo da área de campeo = 18,3 km2) comprendida entre as illas de Sagres, o illote de Noro e a zona de O Carreiro.
  • Os corvos de Cíes desprazáronse por áreas moito máis estensas, (polígono mínimo convexo da área de campeo = 539 km2 e 384 km2) e máis utilizaron con asiduidade tanto zonas do Parque noutros arquipélagos, fundamentalmente Sálvora, como zonas fóra do Parque (Castiñeiras, illa de Arousa, Ría de Aldán e Liméns).
  • Existiron considerables diferenzas entre individuos na estensión da área de campeo e no padrón de distribución no territorio do Parque. Dun lado o individuo de Sagres cunha área de campeo moi reducida e que limita a súa actividade dentro do Parque ao arquipélago de Sálvora. Doutro, os dous individuos de Cíes cunha área de campeo que se estende pola banda esterior das rías de Vigo, Pontevedra e Arousa e que, dentro do Parque, utilizan maiormente os arquipélagos de Cíes e Sálvora.

The outcomes of the 2019 census of breeding European shags suggest a slight increase in their numbers compared to recent years; however, the breeding success of all monitored populations was rather poor. The 2019 census of breeding yellow-legged gulls indicated that the population experienced a sharp decline since the mid 2000’s thus confirming earlier observations from monitoring sectors. Lesser black-backed gulls experienced a slight increase in the number of breeding pairs; currently, this population seems to be confined to the island of Sálvora. Two male shags from Cíes were successfully deployed with GPS/GSM transmitters in early May which together with the female shag deployed in June 2018 transmitted 10,000 GPS locations from January to September 2019. GPS data showed large variations among individual shags both in range size and distribution patterns and a large overlap between individual home ranges.