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First complete census of Cory’s Shearwaters Calonectris diomedea borealis breeding at Berlengas Islands (Portugal), including the small islets of the archipelago
No full textO arquipélago das Berlengas, situado na costa ocidental portuguesa, concentra a maioria da população reprodutora da Cagarra Calonectris diomedea borealis da costa Atlântica continental da Península Ibérica. Em Junho de 2010 e de 2011 foi realizado o primeiro censo global do arquipélago tendo-se estimado a população reprodutora em 980-1070 casais, dos quais 170-210 casais se encontravam dispersos por oito pequenos ilhéus. Até à data não era ainda conhecida a importância dos pequenos ilhéus para a nidificação da Cagarra. Apesar de representarem uma área de ca. 10% da superfície terrestre, os oito ilhéus albergam ca. 20% da população reprodutora
Integrating vessel monitoring systems (VMS) data with daily catch data from logbooks to explore the spatial distribution of catch and effort at high resolution.
No full textDifferent Means to the Same End: Long-Distance Migrant\ud Seabirds from Two Colonies Differ in Behaviour, Despite\ud Common Wintering Grounds
No full textAlthough seabirds that are trans-equatorial migrants show apparently broad overlap among populations in the nonbreeding season, such large-scale pattern may conceal subtle but nevertheless key differences in migratory behaviour. These specializations could reflect adaptation to different environments during the breeding season, carry-over effects from the breeding to the nonbreeding period, or asymmetries in competitive ability of birds of different origin. We compared the migratory and wintering behaviour of Cory’s shearwaters Calonectris diomedea nesting in Berlengas and in the Selvagens, two colonies in contrasting oceanographic environments, separated by ca. 1200 km. Although no differences were found in winter distribution, there was a marked divergence in timing, route and the use of staging areas during the postbreeding\ud
(autumn) migration. Birds from Berlengas typically travelled to oceanic waters in the North Atlantic for an extended stopover, whereas those from Selvagens rarely did so. In the South Atlantic, birds from Selvagens spent more time in flight, perhaps because they had higher energy and nutrient requirements for feather replacement compared to birds from Berlengas, which moult more flight feathers during breeding. Stable isotope analyses of feathers suggested that this variation in activity patterns was unrelated to trophic ecology. Differences in migration routes and stopovers may expose populations to distinct threats, and should be taken into consideration when defining units for conservation purposes and developing appropriate management strategies
First complete census of Cory’s Shearwaters\ud Calonectris diomedea borealis breeding at\ud Berlengas Islands (Portugal), including the\ud small islets of the archipelago
No full textO arquipélago das Berlengas, situado\ud
na costa ocidental portuguesa, concentra a maioria\ud
da população reprodutora da Cagarra Calonectris\ud
diomedea borealis da costa Atlântica continental da\ud
Península Ibérica. Em Junho de 2010 e de 2011 foi\ud
realizado o primeiro censo global do arquipélago\ud
tendo-se estimado a população reprodutora em\ud
980-1070 casais, dos quais 170-210 casais se\ud
encontravam dispersos por oito pequenos ilhéus.\ud
Até à data não era ainda conhecida a importância\ud
dos pequenos ilhéus para a nidificação da Cagarra.\ud
Apesar de representarem uma área de ca. 10% da\ud
superfície terrestre, os oito ilhéus albergam ca. 20%\ud
da população reprodutora
Segmentation of the Portuguese bottom-trawl and purse-seine fleets based on the analysis of landings composition by trip.
Get PDFA classification of the fishing activities based on the trips landing profiles was carried out using a method of non-hierarchical clustering, Partition Around Medoids. Two Portuguese fleets were investigated, the bottom-trawl and the purse-seine fleets, operating off the Portuguese continental coast in the period 2003-2005. In the bottom trawl group, two fleet components were analysed, one targeting finfish and the other directed at crustaceans. Finfish trawl trips produced three groups in 2003 and 2004, one directed at horse mackerel (Trachurus trachurus), a second one targeting octopus and squids and a third one directed at a mixture of species. In 2005 a new group of trips was detected targeting blue whiting (Micromesistius poutassou). In the case of the crustacean trawl trips, in 2004-2005, two trip types were identified, one group targeting deepwater rose shrimp (Parapenaeus longirostris) and another directed at Norway lobster (Nephrops norvegicus). In 2003, two groups were also detected, one directed at deepwater rose shrimp and the other at a mixture of the two main crustacean species. The crustacean trips’ grouping reflects the interannual variation of the abundance of these two species. The analysis of the purse-seine trips produced four fishing activities that remained consistent over the period. Around 72 % of the trips were classified as targeting sardine (Sardina pilchardus). The other clusters were directed towards horse mackerel, Spanish mackerel (Scomber colias) and a mixture of small pelagic species
Developing reliable, repeatable, and accessible methods to provide high-resolution estimates of fishing-effort distributions from vessel monitoring system (VMS) data.
No full textPre-breeding period in Cory’s shearwater:\ud bird quality and foraging behaviour
No full text1. The pre-breeding period in Cory’s shearwater Calonectris diomedea is certainly the\ud
less studied stage in the life cycle of this species. Yet, it is especially during this\ud
period when the purposes of energetic expenditure vary between sexes leading to\ud
possible dimorphisms in their foraging ecology. Namely, females will have to cope\ud
with the costs of egg production whereas males will engage in nest defense from\ud
conspecifics competitors.\ud
2. During the incubation and chick rearing period, the foraging ecology patterns are\ud
determined by the presence of the egg and later the chick. However, no studies have\ud
yet assessed which traits influence the foraging ecology of this species during the prebreeding\ud
period and moreover for each sex.\ud
3. Thus, this study focused on two major aspects that could influence the foraging\ud
ecology of Cory’s shearwater in males and females during the pre-breeding period:\ud
the nest quality and ocean productivity. To do so, nests were characterized by their\ud
physical features, previous breeding success and current occupancy rates. On the\ud
other hand, 33 individuals (16 females and 17 males) were instrumented with GPSloggers\ud
to record their at-sea behavioural patterns. This data was then analyzed with\ud
low and high resolution remote sensing measurements of marine primary productivity\ud
(Chl-a, SST and bathymetry) to additionally test for the influence of the resolution of\ud
remote-sensing spatial and temporal resolution on the interpretation of behavioural\ud
patterns displayed Cory’s shearwaters and other marine predators .\ud
4. Results show that male’s behavioural patterns are strongly influenced by nest\ud
variables associated to quality. Furthermore, this study suggests that the success of\ud
males in gaining a proper nest during the pre-laying will define the outcome of the\ud
II\ud
coming breeding season for that pair, revealing that only high quality individuals will\ud
get the chance to breed. Yet, such quality differences within males were not obvious\ud
in terms of at sea behavioural patterns and foraging ecology.\ud
Females on the other hand did not show any specific patterns related to nests,\ud
however they showed to forage at considerable less productive areas than males\ud
during this period suggesting that they might be searching for very specific nutrients\ud
rather than prey availability. Furthermore males and females showed to forage in\ud
areas that are slightly less productive than the richest areas found within their home\ud
range, which suggests that a small mismatch with respect to primary productivity still\ud
exists.\ud
Last but not least, the results of this study suggest that the use of low-resolution\ud
remote sensing products in combination with highly-accurate tracking devices may\ud
lead to Type I errors.\ud
5. Application: The design of marine important bird areas (mIBAS) in the North\ud
Atlantic System is strongly based on Cory’s shearwaters foraging ecology.\ud
Behavioural dimorphisms in foraging ecology of this species during the pre-laying\ud
period should be taken into account in the design process as they reveal different\ud
patterns and habitat use as during the incubation and chick-rearing period
Censo da População\ud Reprodutora da Cagarra\ud na Ilha da Berlenga em 2010
No full textO arquipélago das Berlengas constitui o local mais importante da costa continental portuguesa para\ud
a nidificação de aves marinhas. Este é também o único local da costa continental onde a Cagarra\ud
Calonectris diomedea, uma espécie com estatuto de conservação desfavorável, nidifica. Nos últimos\ud
20 anos, a população nidificante na ilha da Berlenga tem vindo a ser monitorizada relativamente a\ud
vários aspectos da sua biologia e ecologia. Em 2010 foi efectuado um censo de modo a estimar a\ud
dimensão da população reprodutora na ilha da Berlenga, bem como calculado o sucesso reprodutor.\ud
A população foi estimada em 300 casais reprodutores, apresentando uma tendência favorável.\ud
Medidas de conservação como a declaração da ilha como Reserva Natural e a construção de ninhos\ud
artificiais parecem ter contribuído para este crescimento. O sucesso reprodutor foi de 60.4%, um valor\ud
relativamente baixo, tal como em anos anteriores, que deverá estar relacionado com a presença do\ud
Rato-preto Rattus rattus na ilha. Esta e outras ameaças deverão continuar a ser monitorizadas
Flight dynamics of Cory’s shearwater foraging in a coastal environment
No full textFlight dynamics theories are influenced by two major topics: how birds adapt their flight to cope with heterogeneous habitats, and whether birds plan to use the wind field or simply experience it. The aim of this study was to understand the flight dynamics of free-flying Cory’s shearwaters in relation to the wind characteristics on the coastal upwelling region of continental Portugal. We deployed recently miniaturised devices—global positioning system loggers to collect precise and detailed information on birds’ positions and motions. Prevalent winds were blowing from the north-east and adults used those winds by adjusting their flight directions mainly towards north-west and south-west, flying with cross and tail winds, respectively, and avoiding head winds. This is confirmation that Cory’s shearwaters use a shear soaring flying strategy while exploiting the environment for food: adults foraged mainly with cross winds and their ground speed was not constant during all foraging trips as it changed dynamically as a result of the ocean surface shear winds. During travelling phases, ground speed was strongly influenced by the position of the bird with regard to the wind direction, as ground speed increased significantly with increasing tail wind component (TWC) values. Adults appear to choose foraging directions to exploit ambient wind, in order to improve shear soaring efficiency (cross winding) and exploit diurnal changes in tail wind strength to maximise commuting efficiency. We report, for the first time, precise ground speed values (GPS-derived data) and computed actual flight speed values (using TWC analysis) for Cory’s shearwater
Individual responses of seabirds to commercial\ud fisheries revealed using GPS tracking, stable\ud isotopes and vessel monitoring systems.
Get PDF1. The large amount of discards produced by commercial fisheries can have major impacts on marine predator populations: this abundant food may increase populations of some scavengers or decrease others via accidental bycatch. Yet, despite the conservation implications of discard practices, the ecology of individual scavengers is poorly understood.\ud
2. Here, we assess the influence of commercial fisheries’ activity on the foraging behaviour of individual breeding northern gannets Morus bassanus. Using recent developments in stable isotope mixing models (Stable Isotope Analysis inR or SIAR) we estimate individual discard consumption.\ud
Using GPS tracking and the Vessel Monitoring System (VMS), we investigate behavioural responses to trawlers.\ud
3. Analysis of conventional diet samples, as well as stable isotope ratios of carbon and nitrogen in blood (plasma and cells), highlight marked individual differences in the proportion of fishery discards in the diet. Individual differences in foraging behaviour revealed by stable isotopes show evidence of both short-termconsistency and behavioural flexibility.\ud
4. At-sea path tortuosity of 25 gannets (tracked using GPS loggers) revealed scale-dependent adjustments in response to VMS-derived fishing vessel locations, as well as to sea surface temperature, chlorophyll a concentration and copepod abundance. The results also indicate individual\ud
variability in behavioural response to trawlers.\ud
5. Individual differences in the amount of discards estimated from SIAR were negatively correlated with differences in foraging trip length and body condition, indicating potential fitness consequences.\ud
6. Synthesis and applications. The management of commercial fisheries and apex predators is a daunting task. Ultimately, reducing bycatch and removing dependency on discards remain key conservation priorities, but managers should also ensure that scavenging species have sufficient\ud
alternative food to meet their energetic needs, to ameliorate potential unforeseen knock-on consequences. The results of Stable Isotope Analysis (SIAR) reveal intra-population differences in discard consumption by gannets; differences that have impacts on foraging effort and body condition. The use of GPS tracking and Vessel Monitoring Systems (VMS) reveal that gannet at-sea behaviour is influenced by fishing vessels, although this also varies among individuals. A combination of SIAR, GPS tracking and VMS can be used to study fishery ⁄ scavenger interactions in detail at the individual level, to answer fundamental questions about scavenging behaviour