ENVIRONMENTAL VARIABILITY AND POPULATION DYNAMICS: ROSEATE TERNS AS MONITORS OF THE AZORES MARINE FOOD-WEBS

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Publications

Do Cory’s Shearwaters Calonectris borealis choose mates based on size?

Publication . Nava, Cristina P.; Kim, Sin-Yeon; Magalhães, Maria C.; Neves, Verónica C.

Many bird species rely on visual cues for mate choice, including those provided by body size or by the size of a body appendage. Mate choice based on size may lead to size-assortative mating, which may in turn have consequences for reproductive performance. In this study, we examined whether body size influences mate choice decisions of Cory’s Shearwater Calonectris borealis, a seabird with nocturnal activity on land. We found evidence of negative assortative mating for bill morphology (nostril height and bill length), but found no assortative mating according to body mass, tarsus length, and wing length. In addition, we investigated the influence of negative assortative mating and individual body size-related traits on reproductive performance, i.e., laying date and breeding success. We found that laying date and breeding success were not correlated with the extent of assortative mating, i.e., the assortatively mating breeders did not lay earlier and were not more likely to breed successfully. However, we found that heavier females (body mass measured during pre-laying) laid later in the season. We discuss these results in the light of possible effects of acoustic signals and foraging strategies on the mating pattern. Furthermore, we suggest that some female attributes may be crucial for breeding success in Cory’s Shearwaters.

2014Journal article

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Migration routes and non-breeding areas of Common Terns (Sterna hirundo) from the Azores

Publication . Neves, Verónica C.; Nava, Cristina P.; Cormons, Matt; Bremer, Esteban; Castresana, Gabriel; Lima, Pedro; Junior, Severino M. Azevedo; Phillips, Richard A.; Magalhães, Maria C.; Santos, Ricardo S.

We describe the migration routes and non-breeding areas of Common Terns (Sterna hirundo) from the Azores Archipelago, based on ringing (banding) recoveries and tracking of three birds using geolocators. Over 20 years, there have been 55 transatlantic recoveries of Common Terns from the Azores population: six from Argentina and 49 from Brazil. The three tracked birds migrated south in different months (August, September, November), but the northern migration was more synchronous, with all leaving in April. The birds were tracked to three areas of the South American coast: the male spent November—April on the northern Brazilian coast (13°N–2°S), whereas the two females first spent some time off central-eastern Brazil (4–16°S; one for 1 week, the other for 3 months) and then moved south to the coast of south-eastern Brazil, Uruguay and northern Argentina (24–39°S). Although caution is needed given the small sample size and errors associated with geolocation, the three tracked terns potentially travelled a total of ∼23 200 km to and returning from their non-breeding areas, representing an average movement of ∼500 km day−1. With the exception of Belém, in northern Brazil, and Lagoa do Peixe, in southern Brazil, the coastal areas used by the tracked birds were also those with concentrations of ringing recoveries, confirming their importance as non-breeding areas for birds from the Azores.

2016Journal article

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Black rat Rattus rattus eradication by trapping allows recovery of breeding roseate tern Sterna dougallii and common tern S.hirundo populations on Feno Islet, the Azores, Portugal

Publication . Amaral, João J. S.; Almeida, Sérgio; Sequeira, Maria; Neves, Verónica C.

Mass trapping successfully achieved elimination of black rat Rattus rattus on Feno islet (1.6 ha), Terceira island (Azores archipelago), thus enabling roseate terns Sterna dougallii and common terns Sterna hirundo to recolonize the islet. Rats were first detected on Feno in 2003, when tern breeding-numbers had decreased dramatically. During 2005 no terns bred on the islet and in 2006 fewer than five common tern pairs attempted to nest. Rat eradication was initiated in September 2006. The last rats were captured in March 2007. Monitoring conducted in September 2007, and May and September 2008 indicated that rats had not recolonized. Common terns quickly resumed breeding on Feno islet but numbers (c.120 pairs in 2009) are still below peak levels (c.240-280 pairs) recorded before rat infestation. Roseate terns on the other hand were slower to return but recovered faster with around 260 pairs in 2009, representing 22% of the Azores population. The success of the black rat eradication shows that surveillance and timely action are fundamental to conserve tern colonies vulnerable to rat predation in the Azores.

2010Journal article

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Leapfrog migration and habitat preferences of a small oceanic seabird, Bulwer's petrel (Bulweria bulwerii)

Publication . Ramos, Raül; Sanz, Víctor; Militão, Teresa; Bried, Joël; Neves, Verónica C.; Biscoito, Manuel; Phillips, Richard A.; Zino, Francis; González-Solís, Jacob

AIM: Our current understanding of migratory strategies and the reasons for their high variability along the phylogenetic tree remains relatively poor. Most of the hypotheses relating to migration have been formulated for terrestrial taxa; classically, oceanic migrations were considered as merely dispersive because of the scarcity of observations in the open ocean. We describe for the first time, the migration strategy of a small seabird, the Bulwer's petrel (Bulweria bulwerii), and provide new insights into the ecology and evolution of long-distance marine migrations. LOCATION: Subtropical and tropical Atlantic Ocean. METHODS: Using cutting-edge geolocators, we examined the year-round distribution and at-sea activity patterns of adult Bulwer's petrels sampled at five localities throughout the species' breeding range in the Atlantic, within the Azores, Salvages, Canary and Cape Verde archipelagos. We assessed the migratory connectivity of the species and its habitat use at population and metapopulation scales. RESULTS: Our results provide the first evidence of an oriented leapfrog migration in oceanic seabirds. Ecological niche models based on breeding-season data effectively predicted that subtropical waters of the South Atlantic would be the preferred habitat for the northern populations of Bulwer's petrels during the non-breeding season. Habitat modelling also highlighted similarities in distributions between the breeding and non-breeding periods for the southern populations. Data on at-sea activity patterns suggested that birds from the northern and southern populations behave differently during the breeding season, as well as in the northern and southern non-breeding ranges during the non-breeding period. MAIN CONCLUSIONS: These results indicate that specific habitat preferences, presumably related to differences in prey availability, explain the observed distributions and hence the pattern of leapfrog migration described for Bulwer's petrel. Our study demonstrates the utility of integrating diverse tracking data from multiple populations across international boundaries, and habitat modelling, for identifying important areas common to many marine species in the vast oceanic environments.

2015Journal article

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