64 Proceedings of the Royal Physical Society. 



which pervaded the inhabited burrows which run through 

 and through the thick walls of the old buildings, the latter 

 of which, mixed with earth and turf as they were, afforded 

 unequalled facilities to the birds for the purpose. 



Five minutes' steady digging, and the first petrel with its 

 Qgg was brought to light. I examined it eagerly, and was 

 delighted to find it was a specimen of Leach's, or the fork- 

 tailed petrel {Procellaria leitcorrhoa) . Subsequently we dug 

 out twenty-two more, with their eggs, all within an hour and 

 a half, and could easily have obtained a great many others 

 had we wished. 



This colony is, I therefore imagine, one of the principal 

 breeding stations of this species in the Eastern Hemisphere, 

 and certainly the largest in Great Britain, the only other yet 

 known being on one of the St Kilda group, found by Sir 

 William Milner in 1847. Mr Gray also states, in his work 

 on the " Birds of the West of Scotland," that it breeds on the 

 island of Kum ; but this, I should think, requires corroboration. 

 I have searched the portion of the island mentioned twice 

 without finding any traces of them, and other ornithologists 

 have been equally unsuccessful. I cross-questioned several of 

 the Bum shepherds, who at first said that petrels did breed on 

 that island ; but when I asked them to describe the bird, they 

 accurately described the Manx shearwater {Puffinus anglorum), 

 which does breed in Bum in great numbers, and where I have 

 taken their eggs. Mr Elwes, in his article on "The Bird 

 Stations of the Outer Hebrides," ^ mentions it breeding, along 

 with the stormy petrel, on Berneray or Barra Head island, 

 but does not give certain data. The Leach's petrels on 

 Bona seemed to build in small companies, one large main 

 burrow in the walls of the ruins serving for several pairs of 

 birds, which made smaller burrows branching off at right 

 angles to the main one. 



I found a burrow on the top of the hill at the east end of 

 the island, so I imagine they breed all over the island wher- 

 ever there are suitable situations. 



Leaving the petrels, I started to explore the island. I was 

 rather surprised to find a small flock of curlews among the 



i Ibis, 1869, p. 20. 



