Marco Favero

Environmental and operational variability affecting the mortality of Black-browed Albatrosses associated with long-liners in Argentina

Abstract The effects of different environmental and operational factors on the incidental capture of Black-browed Albatross (Thalassarche melanophris) in long-line fishing operations were analysed. This is the most commonly captured seabird by Argentine long-line fishing vessels, and significant decreases in its populations have been mainly attributed to long-line fishing practices. The estimated mean rate ± s.d. of by-catch for the analysed period (1999–2003) was 0.03 ± 0.39 birds per 1000 hooks. Black-browed Albatrosses were mainly caught during day settings. Higher capture rates were observed during autumn and winter. The effect of the length of long-lines on the incidental capture of Black-browed Albatrosses was also analysed, showing that higher capture rates occurred when short long-lines were deployed. Seasonal differences in the distribution of captures were observed, being widely distributed to the north of the shelf-break during autumn—winter (i.e. non-breeding season) and mostly concentrated in southernmost latitudes, closer to the presumed breeding area in the Malvinas (Falkland) Islands during spring—summer. Mortalities during winter were mainly associated with the Patagonian Toothfish (Dissostrichus eleginoides) fishery, while those observed during summer were associated with long-liners targeting Kingklip (Genypterus blacodes) on the Patagonian Shelf.

Trace metals (Cd, Cr, Cu, Fe, Ni, Pb, and Zn) in feathers of Black-browed Albatross Thalassarche melanophrys attending the Patagonian Shelf

We investigated the concentrations of cadmium, chromium, copper, iron, nickel, lead and zinc among feather tissues in sexes of Black-browed Albatross Thalassarche melanophrys killed in longliners off Argentina in 2005. We found no different metal concentration with sex for cadmium, copper, iron, lead and zinc in feathers of adult birds, though there were significant body-size differences between sexes. However, the concentrations of trace metals differed significantly among the type of feather within individual bird. The mean concentrations of copper, iron, and zinc in breast feathers of T.xa0melanophrys were lower than those reported for the species from Georgias del Sur/South Georgia, the southern Indian Ocean and for other seabirds worldwide. While cadmium fall within the known range of concentrations for bird feathers lead were not. Our results may be indicating that level of pollution in Patagonia may not be as negligible as previously thought at least for some trace metals.

Kleptoparasitism during courtship in Sterna hirundo and its relationship with female reproductive performance

Kleptoparasitism is a well-known foraging tactic used opportunistically by many seabird species. However, little is known about this behaviour during the early stages of the breeding cycle and its effects on breeding performance. Here, we investigated the relationship between kleptoparasitism during the courtship period and female reproductive performance in Common Terns (Sterna hirundo). All identified kleptoparasites were males, and none of their mates performed such behaviour. We compared two groups of tern pairs, one where the males performed kleptoparasitism (kleptoparasitic group, nxa0=xa010), the other one where both mates were non-kleptoparasitic (honest group, nxa0=xa022). The body mass of kleptoparasitic females was between 8 and 15% higher than that of honest females. In kleptoparasitic females, the third egg was significantly bigger than in honest birds, and the egg-volume was not significantly different between the three eggs of the clutch in contrast to honest birds. We found no differences in the comparison among hatching success between both groups. The reproductive output, however, was significantly higher in the kleptoparasitic than in the honest group. Hence, we are providing the first evidence that kleptoparasitism during early stages of the breeding cycle has a strong link with egg size and reproductive output in Common Terns.

Foraging behaviour and diet of American Oystercatchers in a Patagonian intertidal area affected by nutrient loading

Abstract Eutrophication increases the biomass of opportunistic green macroalgae that covers intertidal zones, and macroalgal blooms may affect the intertidal invertebrate community and predation of invertebrates by shorebirds. In San Antonio Bay, Argentina, eutrophication from the discharge of wastewater from a coastal town produces periodic macroalgal blooms. Our aim was to assess if macroalgal blooms affect the foraging behaviour and diet of the American Oystercatcher (Haematopus palliatus). A macroalgal transplant experiment was performed in order to evaluate how epifaunal species respond to a macroalgal canopy. The availability of prey for Oystercatchers, and their foraging behaviour and diet, were analysed in two paired channels with different nutrient loadings. Oystercatchers generally ate the most profitable prey and avoided prey with a profitability value lower than the mean rate of energy intake. During the macroalgal blooms, Oystercatchers avoided two prey species with high profitability values, shifting their foraging strategy and feeding onto a suboptimal prey but with a high encounter rate. Our results suggest that nutrient loadings and the macroalgal blooms that they generate have effects on the diet and foraging behaviour of Oystercatchers, which results in an increase of the average rate of energy intake of Oystercatchers foraging along the channel subject to a macroalgal bloom.

Stealing food from conspecifics: spatial behavior of kleptoparasitic Common Terns Sterna hirundo within the colony site

AbstractAmongst seabirds, kleptoparasitism is one of the most common types of exploitation in which individuals compete for food already procured by another forager. Here, we analyzed the within-colony spatial movements and foraging of transponder-marked Common Terns (Sterna hirundo) during the chick-rearing period in relation to the terns’ trophic strategy (kleptoparasitic vs. honest). Attendance patterns (time spent at the colony site per day, number and locations of resting platforms used) were compared between kleptoparasitic (Nxa0=xa011) and honest individuals (Nxa0=xa026). A total of 725 kleptoparasitic attacks were recorded during the chick-rearing period at the colony site. We found sex differences in the tactic used for stealing food and the area chosen for attacks: females attacked in the vicinity of their nest, while males attacked further away. Significant differences were found between both groups in the spatial pattern: kleptoparasites (particularly males) used more resting platforms and moved more widely across the colony site than honest individuals, and parasitic females were present in the colony longer during the day than honest ones. Our results show a differential use of the colony site dependent on the foraging strategy. Parasitic birds used the colony site as a foraging patch, monitoring the colony and looking for kleptoparasitic feeding opportunities without compromising their parental roles. In contrast, honest individuals spent much time outside the colony foraging for their chicks.ZusammenfassungFutter stehlen bei Artgenossen: Räumliches Verhalten von kleptoparasitischen FlussseeschwalbenSterna hirundoinnerhalb der Kolonien Kleptoparasitismus ist bei Seevögeln eine wichtige Strategie zur Nahrungsbeschaffung, wobei Individuen um Nahrung konkurrieren, die ein anderer Vogel bereits erbeutet hat. In dieser Studie haben wir das räumliche Verhalten von transponder-markierten Flussseeschwalben (Sterna hirundo) in der Kolonie während der Küken-Aufzuchtsphase untersucht. Zusätzlich wurden Fütterungsbeobachtungen in Relation zur Strategie der Individuen (kleptoparasitisch vs. nicht-kleptoparasitisch) durchgeführt. Die Anwesenheitsmuster (verbrachte Zeit pro Tag in der Kolonie, Anzahl der aufgesuchten Rastplätze) zwischen kleptoparasitischen (Nxa0=xa011) und nicht-kleptoparasitischen (Nxa0=xa026) Individuen wurden verglichen. Insgesamt konnten 725 kleptoparasitische Attacken während der Aufzuchtsphase in der Kolonie registriert werden. Bei den Kleptoparasiten haben wir geschlechtsabhängige Unterschiede sowohl bei der angewandten Taktik als auch dem Gebiet, indem die Attacken stattfanden, beobachtet: Während die Weibchen den Artgenossen die Beute vorwiegend in der Nähe ihres eigenen Nestes streitig machten, nutzen Männchen auch weiter weg gelegene Gebiete der Kolonie. Außerdem wurden auch Differenzen im räumlichen Verhalten der beiden Gruppen gefunden: Kleptoparasitische Männchen nutzen mehr Rastplätze und bewegten sich weiter durch die Kolonie als nicht-kleptoparasitische Männchen. Auf der anderen Seite hielten sich die kleptoparasitischen Weibchen pro Tag länger in der Kolonie auf als die nicht-kleptoparasitischen. Unsere Ergebnisse zeigen deutlich eine unterschiedliche Nutzung der Kolonie abhängig von der Strategie bei der Nahrungssuche. Kleptoparasitische Individuen nutzen die Kolonie selbst als Jagdgebiet und warteten bis sich eine Gelegenheit zum Futter stehlen ergab, ohne dabei die elterliche Fürsorge ihrer Jungen zu beeinträchtigen. Im Gegensatz dazu müssen die ehrlich jagenden Flussseschwalben viel Zeit außerhalb der Kolonie zur Nahrungssuche aufwenden, um den Nachwuchs aufzuziehen.

Diversidad de Tetrápodos en un mosaico de ambientes del sudeste de la ecorregión Pampeana como herramienta para planificar en conservación

A pesar del avance en el conocimiento de la biodiversidad para ciertas regiones, este se encuentra en general disperso y no ha sido interpretado respecto a sus propiedades emergentes ni puesto en contextos que faciliten la toma de decisiones en conservacion. El sudeste de la ecorregion Pampas presenta una diversidad ambiental destacada en un area relativamente restringida, y existe ademas una importante cantidad de informacion sobre diversidad de Tetrapodos. Nuestro objetivo fue compilar y analizar este cumulo de informacion, a traves de una lista de especies con sus abundancias relativas por ambientes destacando aquellas endemicas y de interes para la conservacion. Evaluamos la complementariedad entre los taxa (anfibios, reptiles, aves y mamiferos) en terminos de composicion, numero de especies totales y amenazadas. La diversidad de Tetrapodos recopilada pone de manifiesto que esta pequena area presenta una importante riqueza de especies (12 especies de anfibios, 26 reptiles, 233 aves, 34 mamiferos; 41 estan amenazadas y tres son endemicas). Los ambientes representados (pastizales, dunas, sierras, humedales, estuarios, marino, agroecosistemas, urbanizaciones) contribuyen diferencialmente a la diversidad general de Tetrapodos. La distribucion desproporcionada de la riqueza de especies, de especies amenazadas y de la composicion entre ambientes dentro de cada taxon, entre taxa y entre diferentes unidades ambientales destacan la utilidad de este tipo de analisis en la interpretacion de la variacion espacial de la biodiversidad y deberian contribuir en la planificacion territorial en un marco que optimice la conservacion.