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- Colony attendance and moult pattern of Cory's Shearwaters (Calonectris borealis) differing in breeding status and agePublication . Campioni, Letizia; Roda, Sofia Bolumar; Alonso, Hany; Catry, Paulo; Granadeiro, José P.Migratory birds must fit three costly life-history events within the annual cycle, reproduction, moult and migration, to minimize their overlap and maximize survival and breeding success. However, some seabirds, such as Cory’s Shearwater Calonectris borealis, overlap body moult and breeding, with flight feather renewal occurring in late chick-rearing. In contrast, the moult patterns of non-breeding adult (sabbatical) and immature Cory’s Shearwaters, which also attend the colony during the breeding season, remain poorly understood. Furthermore, the potential implications of life-stage and breeding status trade-offs on moult status and colony attendance in non-breeders has rarely been investigated. Surveying different areas within one colony between June and September 2013 and 2014, we studied the age and breeding status composition of birds attending the breeding colony and scored moult of their body (breast and upper-neck), wing and tail feathers. We found that in addition to breeders (n = 165), 57.6% of the birds (n = 389) attending the colony were 4- to 10-year-old immatures (n = 132) and adult sabbatical shearwaters (n = 92). Sabbaticals and 8- to 10-year-old immatures (n = 28) were present at the colony during incubation, whereas only three sabbatical birds and no 8- to 10-year-old immatures were captured in late chick-rearing. Conversely, 4- to 7-year-old immatures arrived later in the season but were still present in late chick-rearing. Sabbatical and 8- to 10-year-old immatures were moulting body feathers at the same time as adult breeders, whereas, among 4- to 7-year-old immatures, older birds moulted earlier than younger birds. A larger proportion of sabbatical birds were replacing tail feathers compared with adult breeders. However, there was no evidence that sabbaticals or 8- to 10-year-old immatures differed in wing moult from adult breeders until August. Overall, our study shows that colony attendance by non-breeding adults and immatures is widespread in this population. The synchronous moult schedule of flight and body feathers across age groups at different life-history stages may suggest that this aspect of moult is controlled by environmental conditions.
- Seabird diet analysis suggests sudden shift in the pelagic communities of the subtropical Northeast AtlanticPublication . Romero, Joana; Catry, Paulo; Alonso, Hany; Granadeiro, José PedroThe dynamics of the subtropical pelagic ecosystems of the Northeast Atlantic are still poorly known due to the high costs associated with sampling large oceanic areas. Top predators can be used as alternative low-cost samplers and indicators of the temporal variability of such systems. To study the variation in the composition of pelagic species through time in the broad Canary current region, we analysed foraging trips and regurgitations of Cory's shearwaters Calonectris borealis nesting on Selvagens islands, in 2008-2011 and 2016-2018. Fisheries data, oceanographic variables and the North Atlantic Oscillation were explored as possible explanatory variables for trends in behaviour and diet. Cory's shearwaters' diet, complemented by fisheries data, revealed marked changes in the composition of the pelagic fish communities. In 2016 there was a peak in the abundance of the Atlantic chub mackerel Scomber colias, followed by an explosive increase in the abundance of the Longspine snipefish Macroramphosus scolopax in 2017 and 2018, as deduced from the diet composition of the Cory's shearwater, and supported by fisheries data, in the broad oceanic area surrounding the Selvagens islands. Oceanographic variables did not show fluctuations correlated with these marked shifts in pelagic fish availability, the causes of which remain largely unknown. This study highlights the importance of the Atlantic chub mackerel and of the Longspine snipefish in the Madeira/Canary region and exemplifies the efficiency of avian predators in revealing rapid changes in pelagic communities of oceanic domains. Such trends and variations need to be better monitored and understood to measure the impact of ongoing global changes and to sustainably manage the marine environment and resources.