The Yelkouan Shearwater or Levantine
Shearwater (Puffinus yelkouan[A]) is a medium-sized shearwater in the seabird
family Procellariidae. It was formerly considered a subspecies of the Manx
Shearwater (Harrison 1988); see there for more on the Puffinus puffinus
superspecies. After the first split (Sibley & Monroe 1990), it was
the nominate subspecies of the so-called "Mediterranean Shearwater" for
nearly ten more years; it is considered a monotypic species nowadays, as
the Balearic form mauretanicus has been separated as Balearic Shearwater
(Wink et al 1993, Heidrich et al 1998, Sangster et al. 2002).
It appears to belong to a group of Mediterranean and adjacent Atlantic
shearwaters which includes the Balearic Shearwater (Austin 1996) 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). The two living Mediterranean lineages had probably separated
before the end of the Pliocene (c.2 mya), as indicated by molecular differences
and putative direct ancestor of the Balearic Shearwater, the Ibizan fossil
Puffinus nestori from the Late Pliocene or Early Pleistocene (Heidrich
et al. 1998).
This species breeds on islands and coastal cliffs in the eastern and central
Mediterranean. Most winter in that sea, but small numbers enter the Atlantic
in late summer. This species nests in burrows which are only visited at
night to avoid predation by large gulls.
Yelkouan Shearwaters are 30-38 cm long, with a 76-89 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 very dark brown to white as the
dark upperparts and paler undersides are alternately exposed as it travels
low over the sea.
The Yelkouan Shearwater has a more contrasted appearance than the Balearic
Shearwater with which its winter range overlaps, since the latter species
is brown above and dirty white below. It is very similar to the black-and-white
Manx Shearwater of the Atlantic, and stray birds out of their usual range
are very difficult to identify with certainty.
Also, at least one mixed breeding colony of the Yelkouan and the Balearic
Shearwater exists on Minorca. A study of these birds recommended that a
combination of morphological characteristics and DNA sequence data should
be required at least for scientific purposes to assign individual birds
to either species (Genovart et al. 2005). The same study concluded that
at least in these westernmost birds, genetic variation was extremely low,
suggesting that the Yelkouan Shearwater may have suffered a marked population
decline historically and thus, while not threatened judging from its absolute
numbers, could be vulnerable to adverse effects of inbreeding.
This is a gregarious species, which can be seen in large numbers from
boats or headlands, especially on in autumn. It is under some threat from
the development of holiday resorts near its breeding sites, and also from
animals such as cats and rats. The Yelkoan Shearwater feeds on fish and
molluscs. It does not follow boats.
It is silent at sea, but at night the breeding colonies are alive with
raucous cackling calls, higher pitched and more drawn out than Manx Shearwater's.
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