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The Balearic shearwater (''Puffinus mauretanicus'') is a medium-sized shearwater in the seabird family ''Procellariidae''. It was long regarded a subspecies of the Manx shearwater (see there for more on the ''Puffinus puffinus'' superspecies); following an initial split it was held to be a subspecies of the "Mediterranean shearwater" (Sibley & Monroe 1990〔Sibley, Charles Gald & Monroe, Burt L. Jr. (1990): ''Distribution and taxonomy of the birds of the world''. Yale University Press, New Haven, CT. ISBN 0-300-04969-2〕) for nearly ten more years, until it was resolved to be a distinct species, separate from the yelkouan shearwater (Wink ''et al.'' 1993,〔Wink, Michael; Heidrich, Petra & Ristow, D. (1993): Genetic evidence for speciation of the Manx shearwater (''Puffinus puffinus'') and the Mediterranean Shearwater (''P. yelkouan''). ''Die Vogelwelt'' 114(6): 226-232. (in English with German abstract ) (PDF fulltext )〕 Heidrich ''et al.'' 1998,〔Heidrich, Petra; Amengual, José F. & Wink, Michael (1998): Phylogenetic relationships in Mediterranean and North Atlantic shearwaters (Aves: Procellariidae) based on nucleotide sequences of mtDNA. ''Biochemical Systematics and Ecology'' 26(2): 145–170. (PDF fulltext ) 〕 Sangster ''et al.'' 2002〔Sangster, George; Knox, Alan G.; Helbig, Andreas J. & Parkin, David T. (2002): Taxonomic recommendations for European birds. ''Ibis'' 144(1): 153–159. (PDF fulltext )〕). It is the last taxon of the ''puffinus'' complex that was recognized as a separate entity. It appears to belong to a group of Mediterranean and adjacent Atlantic species which includes the yelkouan shearwater (Austin 1996〔Austin, Jeremy J. (1996): Molecular Phylogenetics of ''Puffinus'' Shearwaters: Preliminary Evidence from Mitochondrial Cytochrome ''b'' Gene Sequences. ''Molecular Phylogenetics and Evolution'' 6(1): 77–88. (HTML abstract)〕) and one to three prehistorically extinct taxa, Hole's and possibly also Olson's shearwater and an undescribed form of unclear distinctness from Menorca (Alcover 2001〔Alcover, Josep Antoni (2001): Nous avenços en el coneixement dels ocells fòssils de les Balears. ''Anuari Ornitològic de les Balears'' 16: 3-13. (in Catalan, English abstract ) (PDF fulltext )〕). Hole's shearwater may be the closest known relative of ''P. mauretanicus''. The two living Mediterranean lineages had probably separated before the end of the Pliocene (c. 2 mya), as indicated by molecular differences and the Ibizan fossil ''Puffinus nestori'' from the Late Pliocene or Early Pleistocene, which may have been the direct ancestor of the present species (Heidrich ''et al.'' 1998〔). This species breeds on islands and coastal cliffs in the Balearic islands. Most winter in that sea, but some enter the Atlantic in late summer, reaching north to Great Britain and Ireland. This species nests in burrows which are visited only at night to avoid predation by large gulls. This bird is approximately 33 cm long, with an 85–90 cm wingspan. It has the typically "shearing" flight of the genus, dipping from side to side on stiff wings with few wingbeats, the wingtips almost touching the water. This bird looks like a flying cross, with its wing held at right angles to the body, and it changes from dark brown to dirty white as the dark upperparts and paler undersides are alternately exposed as it travels low over the sea. Apart from the less contrasted plumage, this species is very similar to the Atlantic Manx shearwater and the yelkouan shearwater found elsewhere in the Mediterranean. There exists at least one mixed breeding colony of Balearic and yelkouan shearwaters, on Minorca, and the species' winter ranges overlap in the Central Mediterranean; for scientific purposes at least, a combination of morphological characteristics and DNA sequence data is suggested to identify the species (Genovart ''et al.'' 2005). It is under severe threat from the development of holiday resorts near its breeding sites, which can destroy or alter their natural breeding habitat (e.g. producing light pollution around nesting colonies 〔Rodríguez et al. (2005) Artificial lights and seabirds: is light pollution a threat for the threatened Balearic petrels? ''Journal of Ornithology'' 〕), and also from introduced animals such as cats and rats. The discovery of yelkouan shearwaters in the Minorcan colony suggests that hybridization may also pose a problem (Genovart ''et al.'' 2005〔Genovart, Meritxell; Juste, Javier & Oro, Daniel (2005): Two sibling species sympatrically breeding: a new conservation concern for the critically endangered Balearic shearwater. ''Conservation Genetics'' 6(4): 601–606. (HTML abstract)〕); the Balearic shearwater is considered critically endangered with extinction by the IUCN. Recent models estimate a mean decrease of 7.4% per year and a mean extinction time of 40.4 years. This equates to an ongoing decline of more than 80% over the next three generations (54 years). This is a gregarious species, which can be seen in large numbers from boats or headlands, especially in autumn. It is silent at sea, but at night the breeding colonies are alive with raucous cackling calls, higher pitched than the Manx shearwater's. The Balearic shearwater feeds on fish and molluscs. It does not follow boats. ==References== 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Balearic shearwater」の詳細全文を読む スポンサード リンク
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