LEACHES FORK-TAILED PETREL. 443 



PROCELLARL\ LEACHL 

 LEACH'S FORK-TAILED PETREL. 



(Plate 56.) 



Procellaria leucorhoa, Vieill. N. Diet. d'Hist. Nat. xxv. p. 422 (1817). 



Procellaria leachii, Temm. Man. d'Orn. ii. p, 812 (1820) ; et auctorum pluri- 



moium— (Bonaparte), (Nutfall), (Audubon), (Lawrence), (Baird), &c. 

 Hydrobates leachii (Tenun.), Boie, Isis, 1822, p. 562. 

 Procellaria buUockii, Flem. Brit. Anim. p. 13G (1828). 

 Thalassidroma bullockii (Flem.), Selby, Brit. Orn. ii. p. 537 (183.3). 

 Thalassidruma leacliii (Temm.), Bonap. Comp. List B. Eur. S)- N. Amer. p. 64 



(1838). 

 Cymocborea leucorrhoa ( Vieill.), Coues, Proc. Ac. Nat. Sci. Philad. 1864, p. 76. 

 Thalassidroma leucorhoa ( Vieill.), Bexjl. c^- Gerhe, Orn. Eur. ii. p. 387 (1867). 



The Fork-tailed Petrel was first discovered in the British Islands by 

 Bullock iu St. Kilda in the summer of 1818^ a year after it had been 

 described by Vieillot as a new species from an example obtained near 

 Boulogne. It is only known to breed at two places within the limits of 

 the British Islands — on the St.-Kilda group and on North Rona^ off the 

 west coast of Scotland. Elwes was informed by the natives that it breeds 

 on Mingalay, and Gray states that there is an extensive colony on Rum 

 (islands oflF the west coast of Scotland), but there is as yet no confirmatory 

 evidence that such is the case. As a straggler or a storm-driven visitor 

 this bird is known on most parts of the coasts of England, Scotland, and 

 Ireland, and, like the Stormy Petrel, it is sometimes driven far inland by 

 stress of weather. 



Leach's Fork-tailed Petrel is apparently one of the very few birds whose 

 geographical area is discontinuous. So far as is known, there are only 

 three breeding- colonies of this species — one in the North Pacific, extending 

 from the Kui'ile Islands to the Aleutian Islands ; the other two in the North 

 Atlantic, one on the islands in the Bay of Fundy, and the other off the 

 Scotch coast on the islands of St. Kilda and Rona. Birds from the two 

 Atlantic colonies may meet and intermarry in mid-ocean, but appear to be 

 absolutely isolated from the Pacific colony. The latter have not been 

 known in winter to stray further south than the Japanese seas, and in the 

 Atlantic Ocean it has not been found further south than Madeira and the 

 Mediterranean, and in neither locality can it be regarded as more than an 

 accidental visitor. 



The nearest ally of Leach's Fork-tailed Petrel is the Sandwich-Island 

 Fork-tailed Petrel, Procellaria cryptoleucura, a slightly smaller biid, a\ ith 

 white bases to all the tail-feathers except the middle pair, 



2g2 



