ocean, fearlessly attacking even the Greater Black-backed 

 Gull, and evincing, in their amazingly raj)id evolutions of 

 flight, when in pursuit of each other, a rapidity of wing 

 which I should imagine surpasses that of any other bird I 

 know. Upon some of the larger islands, where we observed 

 two or more pairs, they were quite distinct, each occupying 

 its own particular spot. There is something very unaccount- 

 able in the variation of plumage of the Lestris Richardsonii ; 

 no other species, with which we are acquainted, assuming as 

 it does, in different individuals at the same time, and in both 

 sexes, and when breeding, and consequently in a state of ma- 

 turity, two distinct variations of plumage ; some being of the 

 deep uniform brown, as in the figure of the Fauna Boreali 

 Americana ; others with all the under parts white, or nearly 

 so. Those of the last mentioned variety are, I should sup- 

 pose, the more adult birds ; they are, I think, larger, as no- 

 ticed by Dr. Edmonston ; this may, however, be accounted 

 ibr by their being much more frequently females than males. 

 The many specimens which my friend, Mr. John Hancock, 

 and myself had an opportunity of dissecting, whilst in Nor- 

 way, being of that sex ; I doubt not, however, that the male 

 is subject to the same change (but very rarely), not having 

 more than twice met with the light-coloured birds in pairs, 

 although I have in hundreds of instances seen a dark and 

 light one together, as well as two dark ones, and in several 

 have killed and dissected them. It is a curious fact that on 

 the Shetland islands the light variety is much less numerous 

 than the other, not bearing a proportion of more than one in 

 six or seven, whilst in Norway they are nearly equal. You 

 are made aware of your approach to their breeding-places, 

 long before you reach them, by their loud, harsh, and most 

 singular cry, more nearly resembling that of a cat tlian 

 of any bird ; nothing can exceed their solicitude as you 

 near their eggs ; seating themselves at a short distance 

 from you, they flutter about and creej) along the ground. 



