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- Year-round variation in the isotopic niche of Scopoli's shearwater (Calonectris diomedea) breeding in contrasting sea regions of the Mediterranean SeaPublication . Campioni, Letizia; Dell'Omo, Giacomo; Vizzini, Salvatrice; De Pascalis, Federico; Badalamenti, Fabio; Massa, Bruno; RUBOLINI, DIEGO; Cecere, Jacopo G.Top marine predators are key components of marine food webs. Among them, long-distance migratory seabirds, which travel across different marine ecosystems over the year, may experience important year-round changes in terms of oceanographic conditions and availability of trophic resources. We tested whether this was the case in the Scopoli’s shearwater (Calonectris diomedea), a trans-equatorial migrant and top predator, by sampling birds breeding in three environmentally different regions of the Mediterranean Sea. The analysis of positional data and stable isotopes (δ13 C and δ15N) of target feathers revealed that birds from the three regions were spatially segregated during the breeding period while they shared non-breeding areas in the Atlantic Ocean. Isotopic baseline levels of N and C (meso-zooplankton) were significantly different among marine regions during breeding. Such variation was reflected at the higher trophic levels of pelagic and demersal fish muscles as well as in shearwater feathers grown in the Mediterranean. δ15N- and δ13C-adjusted values of shearwaters were significantly different among populations suggesting that birds from different breeding areas relied on prey species from different trophic levels. Conversely, the non-breeding spatial and isotopic niches overlapped greatly among the three populations. Shearwater trophic niches during breeding were narrower and segregated compared to the non-breeding period, revealing a high plasticity in trophic resource use. Overall, this study highlights seasonal and region-specific use of trophic resources by Scopoli’s shearwater, suggesting a broad trophic plasticity and possibly a high adaptability to environmental changes.
- Oceanic seabirds chase tropical cyclonesPublication . Ventura, Francesco; Sander, Neele; Catry, Paulo; Wakefield, Ewan; De Pascalis, Federico; Richardson, Philip L; Granadeiro, José P.; Silva, Monica C.; Ummenhofer, Caroline C.In late summer and autumn, the passage of intense tropical cyclones can profoundly perturb oceanic and coastal ecosystems. Direct negative effects on individuals and marine communities can be dramatic, especially in the coastal zone,1–4 but cyclones can also enhance pelagic primary and secondary production.5–9 However, cyclone impacts on open ocean marine life remain poorly understood. Here, we investigate their effects on the foraging movements of a wide-ranging higher predator, the Desertas petrel (Pterodroma deserta), in the mid-latitude North Atlantic during hurricane season. Contrary to previously studied pelagic seabirds in tropical and mid-latitude regions,10,11 Desertas petrels did not avoid cyclones by altering course, nor did they seek calmer conditions within the cyclone eye. Approximately one-third of petrels tracked from their breeding colony interacted with approaching cyclones. Upon encountering strong winds, the birds reduced ground speed, likely by spending less time in flight. A quarter of birds followed cyclone wakes for days and over thousands of kilometers, a behavior documented here for the first time. Within these wakes, tailwind support was higher than along alternative routes. Furthermore, at the mesoscale (hours–weeks and hundreds of kilometers), sea surface temperature dropped and surface chlorophyll sharply increased, suggesting direct effects on ocean stratification, primary production, and therefore presumably prey abundance and accessibility for surface-feeding petrels. We therefore hypothesize that cyclone wakes provide both predictably favorable wind conditions and foraging opportunities. As such, cyclones may have positive net effects on the demography of many mid-latitude pelagic seabirds and, likely, other marine top-predators.
- Size-assortative mating in a long-lived monogamous seabirdPublication . Visalli, Francesca; De Pascalis, Federico; Morinay, Jennifer; Campioni, Letizia; Imperio, Simona; Catoni, Carlo; Maggini, Ivan; Benvenuti, Andrea; Gaibani, Giorgia; Pellegrino, Irene; Ilahiane, Luca; Chamberlain, Dan; RUBOLINI, DIEGO; Cecere, Jacopo G.Mate choice is a key process in animals to optimize the ftness benefts of reproduction, and it is generally guided by phenotypic features of potential partners that mirror reproductive abilities. Assortative mating occurs when there is within-pair selection for specifc functional traits that can confer ftness benefts. Assortative mating can be positive if mates are more similar, and negative if they are more dissimilar than expected by chance. Mate choice is particularly important in long-lived species with biparental care, such as procellariforms that form long term monogamous bonds. We assessed the mating strategy of a sexually dimorphic Mediterranean procellariform, the Scopoli’s Shearwater (Calonectris diomedea), by testing for assortative mating according to bill (in accordance with previous studies on a sister species) and tarsus size (proxy of body size). We found that shearwaters adopted a positive size-assortative mating by tarsus length, while mating for bill size was random. Moreover, tarsus length was positively correlated with the duration of incubation shifts, when individuals are fasting on eggs. The observed assortative mating could be the results of choice by similarity between individuals, likely because partners with similar relative size have similar tolerance to fasting. Alternatively, the observed pattern could be the product of mutual mate choice, with a selection for large size that could confer competitive abilities in nest selection, defense, foraging aggregations and fasting ability. While our data suggest strong assortative mating in the Scopoli’s Shearwater (R=0.4), we cannot fully disentangle the multiple processes at play acting on mate choice.
- Allochrony is shaped by foraging niche segregation rather than adaptation to the windscape in long-ranging seabirdsPublication . Ventura, Francesco; Granadeiro, José P.; Catry, Paulo; Gjerdrum, Carina; De Pascalis, Federico; Viveiros, Filipe; Silva, Isamberto; Menezes, Dilia; Paiva, Vítor H; Silva, MónicaBackground Ecological segregation allows populations to reduce competition and coexist in sympatry. Using as model organisms two closely related gadfly petrels endemic to the Madeira archipelago and breeding with a two month allochrony, we investigated how movement and foraging preferences shape ecological segregation in sympatric species. We tested the hypothesis that the breeding allochrony is underpinned by foraging niche segregation. Additionally, we investigated whether our data supported the hypothesis that allochrony is driven by species-specific adaptations to different windscapes. Methods We present contemporaneous tracking and stable isotopes datasets for Zino’s (Pterodroma madeira) and Desertas (Pterodroma deserta) petrels. We quantified the year-round distribution of the petrels, characterised their isotopic niches and quantified their habitat preferences using machine learning (boosted regression trees). Hidden- Markov-models were used to investigate the effect of wind on the central-place movement speed, and a simulation framework was developed to investigate whether each species breeds at times when the windscape is most favourable to sustain their trips. Results Despite substantial spatial overlap throughout the year, the petrels exhibited diverging isotopic niches and habitat preferences during breeding. Both species used a vast pelagic region in the North Atlantic, but targeted two different mesopelagic ecoregions and showed a preference for habitats mostly differing in sea surface temperature values. Based on our simulation framework, we found that both species would perform trips of similar speed during the other species’ breeding season. Conclusions The different breeding schedules between the species are underpinned by differences in foraging habitat preferences and adaptation to the local environment, rather than to the windscape. Nevertheless, the larger Desertas petrels exploited significantly windier conditions, potentially unsustainable for the smaller Zino’s petrels. Furthermore, due to larger mass and likely higher fasting endurance, Desertas petrels engaged in central-placeforaging movements that covered more ground and lasted longer than those of Zino’s petrels. Ultimately, patterns of ecological segregation in sympatric seabirds are shaped by a complex interplay between foraging and movement