Aberrantly coloured Cory's Shearwater Calonectris diomedea offshore Chalkidiki, northern Greece
Aberantno obarvan rumenokljuni viharnik Calonectris diomedea opazovan v bližini Chalkidike, severna Grčija
Boris P. Nikolov1, Iva P. Hristova-Nikolova2 & Hein van Grouw3
1	Bulgarian Ornithological Centre, Institute of Biodiversity and Ecosystem Research, Bulgarian Academy of Sciences, 1 Tsar Osvoboditel Blvd, BG-1000 Sofia, Bulgaria, e-mail: lanius.bg@gmail.com
2	Climatech Engineering Ltd., 51 Prof. Kiril Popov Str., BG-1700 Sofia, Bulgaria, e-mail: fotobiota@abv.bg
3	Bird Group, Dept. of Zoology, The Natural History Museum, Akeman Street, Tring, Herts, HP23 6AP, UK, e-mail: h.van-grouw@nhm.ac.uk
Cory's Shearwater is a widespread and locally common breeding bird in Greece (Handrinos & Akriotis 1997), and its population is apparently stable in the country (BirdLife International 2004). Although not frequent, birds with aberrant colouration, including albinism, leucism and melanism, have been recorded in various populations of this species, mainly in the Mediterranean, the Canaries and the Azores (Bried et al. 2005). In fact, the terms "albinism" and "leucism" are often used incorrectly and in most of the cases the mutation "brown" is most probably involved. The pigmentation due to the mutation "brown" is very sensitive to light and the plumage will rapidly bleach out completely (Grouw 2010).
We report herewith on the third case of aberrantly coloured Cory's Shearwater recorded in Greece. The first two are known from Crete — an adult male with single depigmented tail feather and two months old juvenile showing asymmetrical distribution of depigmented wing feathers (Ristow & Witte 2004). In the afternoon of 22 Jun 2009, an aberrantly coloured Cory's Shearwater Calonectris diomedea was recorded in the Kolpos Kassandras Gulf (Aegean Sea), offshore Sithonia Peninsula (off the Toroni village), southern Chalkidiki in northern Greece (39o58'04''N, 23o53'50''E). All secondaries of its left wing were apparently all white, while the rest of the plumage, the eye and the bare parts had the colouration that
is normal for this species. The bird and its normally-plumaged mate were observed and photographed closely, from a boat (Figure 1).
Leucism as a possible cause for this aberration was rejected as it is almost always symmetrical and one would expect the primaries to be white rather than the secondaries — the colourless parts are often on the body parts most far away from the back (Grouw 2006). Bad condition and/or nutritional problems can also be excluded as some form of symmetry of the white feathering can be expected as well. Possible cause, of non-genetic origin, could be an old wound or other problem of the left armwing resulting in the loss of the secondaries and a temporary problem with pigmentation during regrowth of these feathers (Sage 1962).
Although a taxonomic split of Calonectris diomedea (Scopoli's Shearwater, mainly Mediterranean breeding range) and C. borealis (Cory's Shearwater, breeding exclusively in the eastern Atlantic) was recently proposed (Sangster et al. 1999), this treatment was not widely accepted and here we stick to the official nomenclature of the International Ornithological Congress (Gill & Donsker 2011). All data of aberrantly coloured birds from both (sub)species are still very few in order to make any thorough comparisons between these taxa in relation to plumage aberrations.
Acknowledgements: We are thankful to Climatech Engineering Ltd. (Bulgaria) for the logistic help during this trip.
Povzetek
Opisano je opazovanje aberantno obarvanega rumenokljunega viharnika Calonectris diomedea dne 22.6.2009 v zalivu Kolpos Kassandras (Egejsko morje), nasproti vasi Toroni na polotoku Sitonija v severni Grčiji. Opazovani osebek je imel vsa sekundarna peresa leve peruti svetle barve, medtem ko so bili ostali deli telesa normalno obarvani. To je tretje opazovanje aberantno obarvanega rumenokljunega viharnika v Grčiji, kjer sta bili pred tem znani dve opazovanji s Krete. Avtorji so zaradi asimetrije kot možen vzrok za aberacijo izključili levcizem. Domnevajo, da bi lahko bila vzrok za aberacijo negenetskega izvora izguba sekundarnih peres zaradi poškodbe ali drugega razloga in kasnejše težave s pigmentacijo pri obnovi teh peres.
References
Birdlife International (2004): Birds in Europe:
population estimates, trends and conservation status.
Figure 1: Aberrantly coloured Cory's Shearwater Calonectris diomedea recorded on 22 Jun 2009 offshore Sithonia Peninsula, southern Chalkidiki in northern Greece; note white secondaries on its left wing (photo: B. Nikolov)
Slika 1: Aberantno obarvan rumenokljuni viharnik Calonectris diomedea, zabeležen 22.6.2009 v bližini polotoka Sithonia, južna Chalkidika v severni Gr~iji; v o~i bodejo bela sekundarna peresa viharnikove leve peruti (foto: B. Nikolov)
BirdLife Conservation Series No. 12. - BirdLife International, Cambridge. Bried, J., Fraga, H., Calabuig-Miranda, P. & Neves, V.C. (2005): First two cases of melanism in Cory's Shearwater Calonectris diomedea. — Marine Ornithology 33: 19-22. Gill, F. & Donsker, D. (eds.) (2011): IOC World Bird Names. Version 2.9. — [http://www.worldbirdnames. org], 23/8/2011. Handrinos, G. & Akriotis, T. (1997): The Birds of Greece.
— Christopher Helm, London. Ristow, D. & Witte, L. (2004): Albinistic cases in adult and juvenile Cory's shearwaters Calonectris diomedea. — Avocetta 28 (1): 31-32. Sage, B.L. (1962): Albinism and Melanism in Birds. —
British Birds 55: 201-225. Sangster, G., Hazevoet, C.J., van den Berg, A.B., Roselaar, C.S. & Sluys, R. (1999): Dutch avifaunal list: species concepts, taxonomic instability, and taxonomic changes in 1977—1998. — Ardea 87: 139—165. van Grouw, H.J. (2006): Not every white bird is an albino: sense and nonsense about colour aberrations in birds. — Dutch Birding 28: 79-89. van Grouw, H.J. (2010): How to recognize colour aberrations in birds (in museum collections). pp. 53-59 In: Louette, M., Cael, G. & Tavernier, W. (eds.):
Proceedings of the 6th European Bird Curators Meeting, 27-28 August 2009, Tervuren. - Journal of Afrotropical Zoology, Special Issue.
Arrived / Prispelo: 31. 1. 2011 Accepted / Sprejeto: 19. 3. 2012