New Publication on Shearwaters!

Genovart, M., Ramos, R., Igual, J.M., Sanz-Aguilar, A., Tavecchia, G., Rotger, A., Militão, T., Vicente-Sastre, D., Garcia-Urdangarin, B., Pradel, R., González-Solís, J. and Oro, D. (2024), Individual Choices of Wintering Areas Drive Adult Survival Heterogeneity in a Long-Lived Seabird. Ecol Evol, 14: e70675. https://doi.org/10.1002/ece3.70675

In a shell:Wintering area preferences and environmental variability drive survival heterogeneity in long-distance migratory seabirds.

 Abstract:Seasonal migration has evolved as an adaptation for exploiting peaks of resource abundance and avoiding unfavourable climatic conditions. Differential migratory strategies and choices of wintering areas by long-distance migratory species may impose varying selective pressures and mortality risks with fitness consequences. Recently developed tracking technologies allow wintering movements of migratory species to be studied. However, these technologies typically involve a limited number of tracked individuals, which gives low statistical power for any robust estimate of survival probabilities. Additionally, when utilising geolocators, data become accessible only upon individual recapture, presenting a potential source of bias. We used multievent modelling to include information of 147 identified wintering tracks in the analysis of 1104 long-term individual capture histories (2000–2022) of migratory seabird Calonectris diomedea and then test if individual preferences for wintering areas may drive heterogeneity in adult survival. 

Photo: P. Arcos

We also examined individual fidelity to wintering areas and tested if climatic and oceanographic conditions, as represented by the wNAO and SOI climatic indices, influenced survival and fidelity. The probability of fidelity to a wintering area was ca. 0.79. Annual changes between areas were influenced by environmental variability driven by the wNAO. Survival probability was influenced by the SOI and differed between wintering areas; these differences coupled with high wintering site fidelity, generated individual heterogeneity in adult survival. Our study reveals that, over the last two decades, some individuals wintered in less suitable areas, with nonnegligible consequences on adult survival, the parameter to which the population growth rate is most sensitive in long-lived species. Winter oceanographic conditions such as stormy weather or the proximity to upwellings probably play a relevant role in driving survival heterogeneity. Further research is needed to enhance our understanding of how the interlinked effects of climate, local selective pressures and individual condition shape population dynamics in migratory species.

 

New Publicatin on Storm Petrel wintering areas!

Militäo, T., Sanz-Aguilar, A., Rotger, A. and Ramos, R., 2022 Non-breeding distribution and at-sea activity patterns of the smallest European seabird, the European Storm Petrel (Hydrobates pelagicus). Ibis doi: https://doi.org/10.1111/ibi.13068

Abstract: Determining the non-breeding distribution and activity patterns of migratory animals is essential to understand the trade-offs across breeding, moulting and migratory periods and to evaluate the differential levels of exposure of these animals to threats throughout the year. By taking advantage of the current miniaturization of geolocators, during the breeding season of 2019, we deployed geolocators on 10 European Storm Petrels Hydrobates pelagicus breeding on Benidorm Island, Western Mediterranean, to determine the distribution and activity patterns of this small seabird species. Of the eight individuals that were recaptured with usable geolocation data, all individuals migrated to the North Atlantic Ocean, ranging between the Canary Islands and south of Iceland. They possibly take advantage of the more productive waters in the North Atlantic areas explored during the non-breeding period compared with the Western Mediterranean areas explored during the breeding period. 

Photo from https://birdguide.club/

This migratory pattern contrasted with the partial migration described for individuals breeding in the Central Mediterranean. Tracked individuals were more synchronous in their prenuptial than in their postnuptial migratory phenology, probably due to a higher probability of breeding success related to earlier arrival to the breeding area. At-sea activity data indicated that individuals spent more time on the water at night (and especially on those nights around the new moon) during the first half of the non-breeding period (matching the dates of the moulting period of the species). Although birds may begin to moult their feathers while breeding, some seemed to overlap the moulting period with the postnuptial migration. Our results show that multi-colony studies are needed to understand the drivers of distinct migratory patterns at intra- and inter-population levels and how small migratory species trade-off the overlap of moult with other energetically demanding activities such as breeding or migrating.

New Publication on European Storm Petrel wintering areas!

Martínez, C, Roscales, J. L., Sanz-Aguilar, A., Gonzalis-Solis, J, 2019. Inferring the Wintering Distribution of the Mediterranean Populations of European Storm-Petrels Hydrobates pelagicus melitensis from Stable Isotope Analysis and Observational Field Data. Ardeola 66(1) 13-32. doi:https://doi.org/10.13157/arla.66.1.2019.ra2

Abstract: Bird migration studies have been given added impetus recently thanks to the miniaturisation of tracking devices. However, tracking methodologies have remained impractical for the smallest pelagic species and so important gaps in knowledge still exist. In the case of the European Storm-petrel Hydrobates pelagicus, while Atlantic populations are thought to overwinter along the south-western African coast, the winter quarters of Mediterranean birds remain more enigmatic. We performed stable isotope analysis (SIA) of C and N on P1, S8 and P10 feathers from 33 adult birds captured in three Atlantic colonies and 156 adult birds in seven western Mediterranean colonies to infer their wintering areas.

From Wikipedia

In addition, we collated all observational field data, both from peer-reviewed publications and the wider literature, to complement our inferences from SIA. Within the Atlantic, isotopic profiles of feathers moulted at the breeding grounds (P1) differed between birds captured at northern Atlantic and Canary Islands colonies, but were similar for feathers moulted in winter quarters (S8 and P10), indicating low migratory connectivity. Isotopic values of feathers from western Mediterranean birds differed from those of Atlantic birds and showed Mediterranean values for all feathers, indicating that the former overwinter in Mediterranean waters. Variance in the isotopic values was greater in winter than in breeding season feathers, suggesting that birds disperse over larger areas in winter. Isotopic values of feathers moulted during the non-breeding period could match a post-breeding movement towards the southern and eastern Mediterranean. This inference matches the distribution of the few winter reports, which are mainly concentrated in the south-central Mediterranean, mostly in the Tunisian Platform. Our results suggest that this region is the principal wintering area of Mediterranean Storm-petrels.—Martínez, C., Roscales, J.L., Sanz-Aguilar, A. & González-Solís, J. (2019). Inferring the wintering distribution of the Mediterranean populations of European Storm-petrels Hydrobates pelagicus melitensis from stable isotope analysis and observational field data.

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