56 HISTORY OF 



numbers of them frequenting the Hebrides in the breeding sea- 

 sons, which is not the case with L. Parasiticus, but is the case 

 with L. Richardsonii ; L. Parasiticus being rather a rare bird on 

 the British shores. 



In general plumage the two birds much resemble each other, 

 the chief and most distinctive mark in the old birds being the 

 difference in length of the elongated centre tail feathers, which, 

 in L. Parasiticus, measure twelve inches, and in L. Richardsonii 

 nine inches ; and in the tarsi, which in the former bird measures 

 one inch and three-eighths, and in the latter one inch and seven- 

 eighths in length. 



