Puffinus yelkouan Acerbi, 1827
Puffinus puffinus Brunn.: Prostov, 1964: 52; Puffinus puffinus yelkouan Acerbi: Patev, 1950: 250; Donchev, 1963: 120.
Conservation status: in Bulgaria: Endangered EN [B1(a+c(i) (iv)+2(a+c(iv)], BDA-III; International: BeC-II.
General distribution. Probably a Mediterranean species breeding in the Mediterranean basin, where over 95% of the world population is located. During the breeding season it goes into the open sea hundreds of kilometers away. Between June and October the population scatters in the Mediterranean and the Black Sea, where it spends the winter.
Distribution and abundance in Bulgaria. A rarely breeding summer visitor, numerous as wandering. It bred in 1938 on St. Ivan Island  and in 1963 and 1964 on St. Toma Island and between the rivers Veleka and Silistar . According to those more than 120 observations available , outside the breeding period it is found along the Black Sea coast in flocks of several tens to over 37 000 individuals . Since 1985 there have been no data of multiplication, but possible and probable breeding was registered in 12 habitats . In the spring and in the autumn it is found along the whole shore in flocks of several individuals each to 10 200 individuals [3, 6]. During the winter, flocks are observed in Atanasovsko Ezero lake  up to the town of Ahtopol .
Habitats. Rocky sea shores (including islands).
Biology. A colonial species whose nests are in underground cavities, often dug up by the birds themselves, or in rock cracks. It lays 1egg that it incubates for 51-53 days, the young bird hatches around the end of June. A fish-eating and nocturnally active species. Most of the time it spends in the open sea in search for food.
Similar species. In the Mediterranean basin, one species, Puffinus puffinus, was described. In 1988, it was divided into two species: P. puffinus and P. yelkouan. In 2000, P. yelkouan was divided into another two species: P. yelkouan and P. mauretanicus .
Negative factors. Understudied. Possible threats: overcatch in industrial fishing, death of hooks or falling into fishing nets, intensive building along the Black Sea coast, lighting of possible breeding places (cape Kaliakra), flooding of areas by crude oil products and other pollution of the sea.
Conservation measures taken. Protected according to the Biological Diversity Act. In the Kaliakra Reserve, the St. Ivan Island Protected Locality, etc., potentially significant territories are protected. Important Bird Areas with considerable aquatories have been proposed for inclusion in the Natura 2000 network .
Conservation measures needed. Preparation of a National Plan for its preservation, working out management plans for the sites of key significance for the species, monitoring, stable use of the fish resources of the Black Sea, preservation of the rocky sections along the shore.
References. 1. Jordans, 1940; 2. Paspaleva-Antonova, 1965; 3. Ornithological Database, BSPB, Sofia; 4. Simeonov et al., 1990; 5. Iankov, 2007; 6. Georgiev et al, 2003; 7. Michev, Profirov, 2003; 8. Kostadinova, Dereliev, 2001; 9. Vinicombe, 2005; 10. Mateeva, Gramatikov, 2007.
Authors: Petar Iankov, Dimitar Georgiev