Browsing by Author "Alonso, Hany Rafael de Drummond Ludovice Garcia"
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- Breaking the routine: Individual Cory's shearwaters shift winter destinations between hemispheres and across ocean basinsPublication . Dias, Maria P.; Granadeiro, José Pedro; Phillips, Richard A.; Alonso, Hany Rafael de Drummond Ludovice Garcia; Catry, PauloThere is growing evidence that migratory species are particularly vulnerable to rapid environmental changes arising from human activity. Species are expected to vary in their capacity to respond to these changes: long-distance migrants and those lacking variability in migratory traits are probably at considerable disadvantage. The few studies that have assessed the degree of plasticity in behaviour of marine animals suggest that fidelity to non-breeding destinations is usually high. In the present study, we evaluated individual flexibility in migration strategy of a highly pelagic seabird, the Cory’s shearwater Calonectris diomedea. Geolocation data from 72 different migrations, including 14 birds that were tracked for more than one non-breeding season, showed a remarkable capacity to change winter destinations between years. Although some birds exhibited high site fidelity, others shifted from the South to North Atlantic, from the western to eastern South Atlantic, and from the Atlantic to Indian Ocean. Individuals also showed flexibility in stopover behaviour and migratory schedule. Although their K-selected lifehistory strategy has the disadvantage that the chances of microevolution are slight if circumstances alter rapidly, these results suggest that Cory’s shearwaters may be in a better position than many other long-distance migrants to face the consequences of a changing environment.
- Estratégias de muda de plumagem e ciclos de afluência à colónia em Cagarras Calonectris diomedea borealisPublication . Alonso, Hany Rafael de Drummond Ludovice GarciaA muda das penas é um processo vital mas dispendioso em termos energéticos para as aves. A ocorrência de outros eventos desgastantes no ciclo anual das aves, como a reprodução e a migração, pressupõe uma calendarização que optimize os custos e benefícios dos vários processos. A cagarra, uma ave marinha que possui uma época reprodutora que ocupa parte considerável do ciclo anual, apresenta uma sobreposição parcial da sua muda das primárias com a época reprodutora, fenómeno pouco usual entre as aves pelágicas. Nas Selvagens, o timing do início da muda das primárias (8,6% das aves estava em muda activa em Setembro) está atrasado em relação à Berlenga, onde 43,7% das aves já se encontrava a mudar as primárias. Estas diferenças dever-se-ão a uma menor disponibilidade alimentar na área envolvente às Selvagens em relação às Berlengas. Este facto é corroborado pelas baixas afluências de indivíduos reprodutores falhados à colónia da Selvagem, ao contrário do que acontece na Berlenga. As aves que falham a reprodução deverão ficar com uma maior disponibilidade temporal e energética para o exercício de outras actividades. Tanto nas Selvagens como nas Berlengas, a proporção de aves que iniciaram a muda das primárias em Setembro é maior em aves que falharam a reprodução (75% nas Selvagens e 90% nas Berlengas), do que em aves que se encontram a alimentar crias (7,7% nas Selvagens e 25,9% nas Berlengas). A disponibilidade alimentar e o sucesso reprodutor são dois factores que influenciam o timing de muda nas cagarras, o que mostra a existência de trade-offs entre a actividade reprodutora e a muda da plumagem, com consequências em termos da ocorrência de diferentes estratégias de muda. As cagarras que nidificam nas Selvagens apresentam ciclos de afluência às ilhas que possuem um padrão bem definido e único. No entanto, pouco se sabe acerca da regulação e funções destes ciclos. Neste estudo, recorrendo a contagens de indivíduos na colónia e informações de actividade recolhidas através de data-loggers, estudámos a estrutura destes ciclos. Encontrámos diferenças na duração dos mesmos, entre a fase de pré-incubação (7,5 ± 1,6 dias) e a fase de incubação/criação (9,3 ±1,3 dias). A amplitude, embora não seja diferente entre as fases, mostrou-se bastante baixa nas primeiras semanas de Abril (0,367 ± 0,165). A afluência à colónia, tanto diurna como nocturna, de machos (0,816 ± 0,098 machos na colónia/total) e fêmeas (0,518 ± 0,052) é diferente, tendo sido mais elevada para ambos no princípio de Abril. A sincronização entre cagarras de diferentes locais da Selvagem Grande está ligeiramente desfasada (em cerca de um dia) e a aparente sincronização dos casais parece resultar do comportamento cíclico de afluência, não sendo maior num casal do que em quaisquer dois indivíduos da colónia. Os factores climatéricos, com excepção da intensidade do vento, não estão relacionados com o número de cagarras presentes na colónia. As diferenças na estrutura dos ciclos entre diferentes fases da época reprodutora estarão relacionados com a elevada afluência à colónia no princípio de Abril. Os desfasamentos temporais nos ciclos entre aves de diferentes áreas sugerem que a sincronia entre as aves da mesma área poderá ser determinante na regularidade dos ciclos e, de forma indirecta, na sincronia entre os membros de cada casal. Muito embora os factores climatéricos na colónia não aparentem ter um papel relevante na regulação dos ciclos, não se pode excluir a hipótese de que outros factores extrínsecos possam intervir na regulação dos mesmos. Palavras-chave: Ciclos de afluência, Calonectris diomedea A muda das penas é um processo vital mas dispendioso em termos energéticos para as aves. A ocorrência de outros eventos desgastantes no ciclo anual das aves, como a reprodução e a migração, pressupõe uma calendarização que optimize os custos e benefícios dos vários processos. A cagarra, uma ave marinha que possui uma época reprodutora que ocupa parte considerável do ciclo anual, apresenta uma sobreposição parcial da sua muda das primárias com a época reprodutora, fenómeno pouco usual entre as aves pelágicas. Nas Selvagens, o timing do início da muda das primárias (8,6% das aves estava em muda activa em Setembro) está atrasado em relação à Berlenga, onde 43,7% das aves já se encontrava a mudar as primárias. Estas diferenças dever-se-ão a uma menor disponibilidade alimentar na área envolvente às Selvagens em relação às Berlengas. Este facto é corroborado pelas baixas afluências de indivíduos reprodutores falhados à colónia da Selvagem, ao contrário do que acontece na Berlenga. As aves que falham a reprodução deverão ficar com uma maior disponibilidade temporal e energética para o exercício de outras actividades. Tanto nas Selvagens como nas Berlengas, a proporção de aves que iniciaram a muda das primárias em Setembro é maior em aves que falharam a reprodução (75% nas Selvagens e 90% nas Berlengas), do que em aves que se encontram a alimentar crias (7,7% nas Selvagens e 25,9% nas Berlengas). A disponibilidade alimentar e o sucesso reprodutor são dois factores que influenciam o timing de muda nas cagarras, o que mostra a existência de trade-offs entre a actividade reprodutora e a muda da plumagem, com consequências em termos da ocorrência de diferentes estratégias de muda. As cagarras que nidificam nas Selvagens apresentam ciclos de afluência às ilhas que possuem um padrão bem definido e único. No entanto, pouco se sabe acerca da regulação e funções destes ciclos. Neste estudo, recorrendo a contagens de indivíduos na colónia e informações de actividade recolhidas através de data-loggers, estudámos a estrutura destes ciclos. Encontrámos diferenças na duração dos mesmos, entre a fase de pré-incubação (7,5 ± 1,6 dias) e a fase de incubação/criação (9,3 ±1,3 dias). A amplitude, embora não seja diferente entre as fases, mostrou-se bastante baixa nas primeiras semanas de Abril (0,367 ± 0,165). A afluência à colónia, tanto diurna como nocturna, de machos (0,816 ± 0,098 machos na colónia/total) e fêmeas (0,518 ± 0,052) é diferente, tendo sido mais elevada para ambos no princípio de Abril. A sincronização entre cagarras de diferentes locais da Selvagem Grande está ligeiramente desfasada (em cerca de um dia) e a aparente sincronização dos casais parece resultar do comportamento cíclico de afluência, não sendo maior num casal do que em quaisquer dois indivíduos da colónia. Os factores climatéricos, com excepção da intensidade do vento, não estão relacionados com o número de cagarras presentes na colónia. As diferenças na estrutura dos ciclos entre diferentes fases da época reprodutora estarão relacionados com a elevada afluência à colónia no princípio de Abril. Os desfasamentos temporais nos ciclos entre aves de diferentes áreas sugerem que a sincronia entre as aves da mesma área poderá ser determinante na regularidade dos ciclos e, de forma indirecta, na sincronia entre os membros de cada casal. Muito embora os factores climatéricos na colónia não aparentem ter um papel relevante na regulação dos ciclos, não se pode excluir a hipótese de que outros factores extrínsecos possam intervir na regulação dos mesmos.
- Ichthyofauna of the Selvagens Islands. Do small coastal areas show high species richness in the northeastern Atlantic?Publication . Almada, Frederico José Oliveira de; Abecasis, David; Villegas-Ríos, David; Henriques, Sofia; Pais, Miguel P.; Batista, Marisa I.; Costa, Bárbara Horta e; Martins, Joana; Tojeira, Inês; Rodrigues, Nuno Vasco; Araújo, Ricardo; Souto, Miguel; Alonso, Hany Rafael de Drummond Ludovice Garcia; Falcón, Jesús M.; Henriques, Filipe; Catry, Paulo; Cabral, Henrique; Biscoito, Manuel; Almada, Vítor CarvalhoThe Selvagens Islands are located in the northeastern Atlantic between the Canary Islands and Madeira Island. As a result of their small size, remote location and harsh sea conditions only a few studies have been conducted to describe their marine species diversity. We were able to identify 29 new coastal fish species, an increase of 33% in the ichthyofauna described for these islands (n = 88). There is a prevalence of species with tropical affinities and only 2.3% (n = 2) are endemic to Macaronesia. Considered a stepping-stone colonization vector from the nearest continental shore, as proposed by other authors for this region, the Selvagens Islands host 34.1% of the ichthyofauna described for the much larger Canary Islands (nspecies = 258, submerged area nSelvagensIs. = 2.3%) and 47.3% of the ichthyofauna described for the more distantly located Madeira Island (nspecies = 186, submerged area nSelvagensIs. = 17.9%). Interestingly, 6.8% (n = 6) of the species failed to bridge the gap between the Selvagens Islands and Madeira Island. Data collected so far showed no trend toward an increasing number of species with high dispersal capability. The Selvagens Islands are an example of a high coastal species diversity occurring even in very small areas of the northeastern Atlantic Ocean.
- Moult strategies of Cory’s Shearwaters Calonectris diomedea borealis: The influence of colony location, sex and individual breeding statusPublication . Alonso, Hany Rafael de Drummond Ludovice Garcia; Matias, Rafael; Granadeiro, José Pedro; Catry, PauloThe replacement of old feathers is essential for birds, but it is also an energy-demanding task. As moult usually does not coincide with other stressful events in its annual cycle, such as reproduction and migration, the bird can optimise its use of time and energy allocated to different activities. There are very few studies comparing the moult strategies of populations with similar breeding calendars but occurring in areas of different habitat quality. Cory’s Shearwaters Calonectris diomedea have a partial moult–breeding overlap, an unusual phenomenon among pelagic seabirds. We have compared the moult schedules in Cory’s Shearwater colonies located in distinct environments (pelagic vs. coastal) and show that moult–breeding overlap is less extensive on Selvagem Grande, situated in deep oceanic waters, than on Berlenga, situated on the continental shelf. Colony attendance of failed breeders, most of which were moulting, was lower at Selvagem Grande than at Berlenga, which suggests that the feeding areas of birds from the former site are more distant from the colony. Failed breeders started to moult earlier than individuals still raising a chick, and breeding status had a stronger influence on determining the onset of wing-feather moult than colony location. Despite published evidence that internal circannual rhythms and external cues, such as variation in daylength, are important factors regulating moult schedules, it is clear that birds retain a considerable flexibility that allows them to respond to external factors in order to strategically manage time and energy in a way that is thought to maximise their fitness.
- Mysterious attendance cycles in Cory’s shearwater, Calonectris diomedea: An exploration of patterns and hypothesesPublication . Granadeiro, José Pedro; Alonso, Hany Rafael de Drummond Ludovice Garcia; Almada, Vítor Carvalho; Menezes, Dília; Phillips, Richard A.; Catry, PauloSeveral species of seabirds show cyclic patterns of attendance at their nesting colonies.We examined the patterns of variation in the numbers of Cory’s shearwater at three colonies (two oceanic and one located on the continental shelf), including the world’s largest, at Selvagem Grande, Madeira, Portugal and considered several hypotheses concerning their causal mechanisms. At Selvagem Grande, cycles were exceptionally marked and regular, with a periodicity ranging from 7.8 to 11 days, and involved both breeders and nonbreeders. In contrast, variation in numbers was aperiodic at a nearby and much smaller colony (Selvagem Pequena), and also at the colony located off the Portuguese coast (Berlenga Island).We found no relationships between number of birds ashore and environmental variables such as wind direction and speed or lunar cycle. Cycles did not seem to be driven by oscillations in food availability or accessibility, given that they did not correlate with daily chick growth rates (which were acyclic) or diet. Despite their regularity, cycles were slightly out of phase in different sectors of Selvagem Grande, which suggests that social interactions at the colony could act as an entrainment agent for an endogenous rhythm, and so cycles are probably more likely to occur in large and dense colonies. Observations are consistent with the hypothesis that cycles facilitate social interactions by maximizing the probability of encounters at the colony. However, the exact mechanisms through which these remarkable cycles are controlled are still completely unknown, and clearly further research is needed.
- Parent–offspring dietary segregation of Cory’s shearwaters breeding in contrasting environmentsPublication . Alonso, Hany Rafael de Drummond Ludovice Garcia; Granadeiro, José Pedro; Paiva, Vitor H.; Dias, Ana S.; Ramos, Jaime; Catry, PauloIn pelagic seabirds, who often explore distant food resources, information is usually scarce on the level of trophic segregation between parents and their offspring. To investigate this issue, we used GPS tracking, stable isotopes and dietary information of Cory’s shearwaters Calonectris diomedea breeding in contrasting environments. Foraging trips at Selvagem Grande (an oceanic island) mainly targeted the distant African coast, while at Berlenga island (located on the continental shelf), shearwaters foraged mainly over nearby shelf waters. The degree of isotopic segregation between adults and chicks, based on d13C, differed markedly between the two sites, indicating that adult birds at Selvagem fed their chicks with a mixture of shelf and offshore pelagic prey but assimilated more prey captured on coastal shelf waters. Isotopic differences between age classes at Berlenga were much smaller and may have resulted from limited dietary segregation or from age-related metabolic differences. The diet of shearwaters was also very different between the two colonies, with offshore pelagic prey only being detected at Selvagem Grande. Our findings suggest that spatial foraging constraints influence resource partitioning between pelagic seabirds and their offspring and can lead to a parent–offspring dietary segregation.
- Temporal and age-related dietary variations in a large population of yellow-legged gulls Larus michahellis : Implications for management and conservationPublication . Alonso, Hany Rafael de Drummond Ludovice Garcia; Almeida, Ana Pereira; Granadeiro, José Pedro; Catry, PauloThere was an extraordinary increase in the numbers of European gulls during the twentieth century which has been linked to higher availability of food derived from human activities. At Berlenga island (Portugal), the population of yellow-legged gulls Larus michahellis increased from 2600 individuals to a peak of 44,698 gulls (1974–1994), after which control measures have been put in place. Despite the management effort, little is known about the feeding ecology of this population. To investigate temporal and age-related variations in the diet of yellow-legged gulls at Berlenga, 1668 adult pellets and 145 chick regurgitates were collected and analysed between 2009 and 2012. Contradicting the generally accepted idea that these birds depend mainly on human-related food, adult gulls relied substantially on a locally abundant natural prey, the Henslow’s swimming crab Polybius henslowii. Nevertheless, large amounts of refuse and fish were consumed in periods of apparent lower availability of swimming crabs. Despite the large temporal shifts in diet and feeding areas (change from marine to terrestrial prey), adult gulls consistently provisioned their chicks with a fish-based diet and chick condition remained constant. These results not only highlight the great resilience of this population to changes in food availability but also indicate that food from different human activities remain highly accessible. With the implementation of recent EU legislation regarding the reduction of fishery discards, and the increase of urban populations in the mainland, the monitoring and appropriate management of gull populations will be decisive for the healthy conservation of coastal systems used by these gulls.
- The diet of a nocturnal pelagic predator, the Bulwer’s petrel, across the lunar cyclePublication . Waap, Silke; Symondson, William O. C.; Granadeiro, José Pedro; Alonso, Hany Rafael de Drummond Ludovice Garcia; Gonçalves, Catarina Serra; Dias, Maria P.; Catry, PauloThe lunar cycle is believed to strongly influence the vertical distribution of many oceanic taxa, with implications for the foraging behaviour of nocturnal marine predators. Most studies to date testing lunar effects on foraging have focused on predator activity at-sea, with some birds and marine mammals demonstrating contrasting behavioural patterns, depending on the lunar-phase. However, to date no study has focused on how the lunar cycle might actually affect predator-prey interactions in the upper layers of the ocean. Here, we tested whether the diet of the predominantly nocturnal pelagic predator, the Bulwer's petrel (Bulweria bulwerii) would change throughout the lunar cycle, using molecular analysis to augment detection and taxonomic resolution of prey collected from stomach-contents. We found no evidence of dietary shifts in species composition or diversity, with Bulwer's petrel always consuming a wide range of mesopelagic species. Other co-variables potentially affecting light availability at-sea, such as percentage of cloud cover, did not confound our results. Moreover, many of the species found are thought not to reach the sea-surface. Our findings reveal that nocturnal predators are probably more specialized than previously assumed, irrespective of ambient-light, but also reveal deficiencies in our current understanding of species vertical distribution and predation-dynamics at-sea.
- When males are more inclined to stay at home :Insights into the partial migration of a pelagic seabird provided by geolocators and isotopesPublication . Perez, Cristóbal; Granadeiro, José Pedro; Dias, Maria P.; Alonso, Hany Rafael de Drummond Ludovice Garcia; Catry, PauloPartial migration has never been studied in pelagic seabirds, but investigating old unresolved questions in new contexts can provide useful fresh insights. We used geolocators and stable isotopes to investigate this phenomenon in a migratory pelagic seabird, the Cory’s shearwater (Calonectris diomedea). Although most birds migrated to the southern hemisphere, 8.1% of studied birds (N = 172) remained close to the breeding colony (Selvagem Grande, Madeira, Portugal), foraging within the Canary current. Almost all resident birds were males, while age or body size did not predict migratory status. Despite displaying a high repeatability (R = 0.72) in the choice of wintering area, residency was not a fixed strategy and individuals could switch between migrating and staying in the Canary current in different years. The predictions resulting from the “body size” and the “social dominance” hypotheses, in which larger individuals or dominant individuals, respectively, remain closer to the breeding areas, were not supported by our data. Resident males were able to occupy the nesting burrows much earlier than migratory males and arrival time in this species is known to affect the probability of engaging in a reproductive attempt. The selective pressure to arrive early at the colony is therefore the most likely explanation for the maintenance of this partial migration system.