Volume 47, No. 2

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Bill malformation in Scopoli's Shearwater Calonectris diomedea chicks


1Ornis italica, Piazza Crati 15, 00199 Rome, IT (
2University of Palermo, Viale delle Scienze, 13, 90128 Palermo, IT
3Berta maris, 92031 Linosa, Agrigento, IT


ROATTI, V., MASSA, B. & DELL'OMO, G. 2019. Bill malformation in Scopoli's Shearwater Calonectris diomedea chicks. Marine Ornithology 47: 175 - 178

Received 18 March 2019, accepted 01 April 2019

Date Published: 2019/10/15
Date Online: 2019/06/20
Key words: bill malformation, Scopoli’s Shearwater, Calonectris diomedea, Procellariiformes, chicks, seabirds


We report three cases of bill malformation in Scopoli's Shearwater Calonectris diomedea on Linosa Island (Sicily, Italy) that were found during monitoring of the colony over a 13-year period. The cases were observed in pre-fledging chicks; two of the birds were also in poorer body condition compared with chicks of the same age. No adults in the colony have been found with similar bill malformations despite a much larger sample of recorded adults. We suggest that the observed malformations impair survival and that the chicks we encountered would likely starve after fledging. The frequency of bill malformation found on Linosa is less than one percent, which is consistent with cases reported in the literature for other species.


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