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As the title of this post indicates, this is the second part of the post ‘What do you know about the Cory's shearwater? (Part I)’.
Both posts are the result of the participation of our biologist Lara Abascal in part of the study and conservation work carried out by the Societat Ornitológica de Menorca (SOM) on Illa de l'Aire. This second part focuses on more specific aspects of its biometrics, for those who want to delve a little deeper into the ornithological knowledge of this fascinating species.
Sexual dimorphism in Cory's shearwaters
The following table shows the measurements (in mm) of various populations of Cory's shearwaters. It indicates the breeding colony, the number of individuals measured (males: females) and the average values ± standard deviation, according to Gómez-Díaz and González-Solís (2007).
Based on the data compiled in the table, it can be stated that there is a certain difference in size between males and females, which allows them to be sexed by taking measurements of the different parts of the body listed in the table. Although there may be some overlap in extreme individuals, broadly speaking it can be said that males are slightly larger, although this may not be obvious at first glance, which is why it is necessary to take measurements if you want to minimise error.
Moulting in the Cory's shearwate
Breeding adults undergo a complete annual moult that overlaps considerably with the breeding season. In the phases prior to laying (April-May) and in the early stages of incubation (May-June), feather renewal is minimal. The cycle begins in the middle of the incubation period (i.e. after mid-June), with the replacement of the breast feathers, progressing downwards and sideways towards the belly and flanks. On the dorsal area of the body, moulting seems to follow the same pattern. As for the flight feathers (the primary feathers and tail feathers), their moulting takes about 200 days, between late August and March, beginning in the middle of the chick-rearing process. The renewal of the primary feathers is simple and descends from the innermost feather (P1) to the outermost (P10). The secondaries show a somewhat more complex pattern, with three unsynchronised starting points: the initial focus occurs in the tertiary feathers (around S22); the second, approximately in the fifth secondary (S5); and the third in the outermost secondary (S1) (see Fig. 1).
Diagram of the moulting process in C. diomedea. According to Ramos et al. (2009).
The moulting of the tail feathers begins at the centre of the tail (R1), progressing towards the outer feathers. The process takes place mostly in wintering areas, since in March-May the process is advanced but not complete, there is a certain suspension until July-August, when it reactivates to conclude, in most birds, before September (Ramos et al., 2008, 2009).
Bibliography Part I and II:
-Carboneras, C.; Derhé, M.; Ramirez, I. 2013. Update on the population status and distribution of Mediterranean shearwaters. Report to Seventh Meeting of the ACAP Advisory Committee, La Rochelle, France, 6-10 May 2013.
-Catchot, S. 1991. Contribució al coneixement de les Procellariiformes a l’Illa de Menorca. Anuari Ornitològic de les Balears 6. 3-12.
-Cortés, V., Arcos, J. M., & González-Solís, J. 2017. Seabirds and demersal longliners in the northwestern Mediterranean: Factors driving their interactions and bycatch rates. Marine Ecology Progress Series, 565, 1–16. https://doi.org/10.3354/meps12026
-Cortés, V., García-Barcelona, S. & González-Solís, J. 2018. Sex-and age-biased mortality of three
shearwater species in longline fisheries of the Mediterranean. Marine Ecology Progress Series588, 229-241.
-Defos du Rau, P.; Bourgeois, K.; Ruffino, L.; Dromzée, S.; Ouni, R.; Abiadh, A.; Estève, R.; Durand, J-P.; Anselme, L.; Faggio, G.; Yahya, J.M.; Peters, P.; Rguibi, H.; Renda, M.; Miladi, B.; Hamrouni, H.; Alilech, S.; Ben Dhafer, A.; Nefla, A.; Jaouadi, W.; Agrebi, S.; Renou, S. 2012. New assessment of the world largest colony of Scopoli’s Shearwater Calonectris diomedea. In: Yésou, P.; Baccetti, N.; Sultana, J. (ed.), Ecology and Conservation of Mediterranean Seabirds and other bird species under the Barcelona Convention – Proceedings of the 13th Medmaravis Pan-Mediterranean Symposium. Alghero (Sardinia) 14-17 Oct. 2011, pp. 26–28. Medmaravis, Alghero.
-Derhé, M. 2012. Developing a Population Assessment for Scopoli’s and Cory’s Shearwaters Calonectris diomedea/Calonectris borealis. In: Yésou, P.; Baccetti, N.; Sultana, J. (ed.), Ecology and Conservation of Mediterranean Seabirds and other bird species under the Barcelona Convention – Proceedings of the 13th Medmaravis Pan- Mediterranean Symposium. Alghero (Sardinia) 14-17 Oct. 2011, pp. 29–38. Medmaravis, Alghero.
-Felicísimo, A. M., Muñoz, J., González-Solís, J. (2008). Ocean surface winds drive dynamics of transoceanic aerial movements. Plos One, 3: e2928.
-Genovart, M., Doak, D. F., Igual, J. M., Sponza, S., Kralj, J., & Oro, D. 2017. Varying demographic impacts of different fisheries on three Mediterranean seabird species. Global Change Biology, 23(8), 3012–3029. https://doi.org/10.1111/gcb.13670
-Genovart, M., Bécares, J., Igual, J. M., Martínez-Abraín, A., Escandell, R., Sánchez, A., Rodríguez, B., Arcos, J. M. & Oro, D. 2018. Differential adult survival at close seabird colonies: The importance of spatial foraging segregation and bycatch risk during the breeding season. Global Change Biology, 24: 1279–1290.
-Genovart, M., Escandell, R., Catchot, S. & Oro, D. 2022. Seguiment de la Baldriga Calonectris diomedea a l’illa de l’Aire, Menorca. Informe inédito. Centro de Estudios Avanzados de Blanes. SOM. 33 pp.
-Igual, J. M., Tavecchia, G., Jenouvrier, S., Forero, M.G. and Oro, D. 2009. Buying years to extinction: is compensatory mitigation for marine bycatch a sufficient conservation measure for long-lived seabirds? PLoS One 4(3): e4826.
-Lo Valvo, M. (2001). Sexing adult Cory's shearwater by discriminant analysis of body measurements on Linosa Island (Sicilian channel), Italy. Waterbirds, 24: 169-174.
-Madroño, A., González, C. & Atienza, J.C. 2004. Libro Rojo de las Aves de España (ed. by A..), pp. 43–45. Dirección General de Conservación de la Naturaleza & SEO/BirdLife, Madrid, España.
-Pascal, M.; Lorvelec, O.; Bretagnolle, V.; Culioli, J. M. 2008. Improving the breeding success of a colonial seabird: a cost-benefit comparison of the eradication and control of its rat predator. Endangered Species Research 4: 267–276.
-Reyes-González, J. M., González-Solís, J. (2016). Pardela cenicienta mediterránea - Calonectris diomedea.En: Enciclopedia Virtual de los Vertebrados Españoles. Salvador, A., Morales, M. B. (Eds.). Museo Nacional de Ciencias Naturales, Madrid.
-Sánchez, A. (1997). La Pardela cenicienta (Calonectris diomedea) en las islas Columbretes: biología y conservación. Universidad de Valencia, Valencia.
-SEO/BirdLife (López-Jiménez, N. Ed). 2021. Libro Rojo de las aves de España. SEO/BirdLife.
-SEO/BirdLife (Molina, B., Nebreda, A., Muñoz, A. R. Seoane, J., Real, R., Bustamante, J. y Del Moral,
-J. C. Eds.) 2022a. III Atlas de aves en época de reproducción en España. SEO/BirdLife. Madrid.
-SEO/BirdLife. 2022b (García, D. & Arcos, J.M.). 2022b. Localización y estima de la población reproductora de la pardela cenicienta en Menorca (islas Baleares). Informe inédito del proyecto Pardeles para la Fundación Biodiversidad, MITECO.
-Wink, M., Ristow, D. (1979). Zur Biometrie des Sexualdimorphismus beim Gelbschnabelsturmtaucher (Calonectris diomedea). Vogelwarte, 30 (2): 135-138.
Text: own work.
Photographs: Lara Abascal.
Acknowledgements: Santi Catchot for his excellent work with the shearwaters of Illa de l'Aire and Lara Abascal for her contribution to the writing of Parts I and II of this entry.
To find out more:
- https://es.wikipedia.org/wiki/Calonectris_diomedea
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