BILLS OF GULLS. 233 



sionally on shore and clear the ploughed land of 

 larvae and worms along with the rooks ; and not a few 

 breed in small lakes and marshes many miles inland, 

 and find marsh food for themselves and their broods. 

 Their bills correspond, as may be seen in the follow- 

 ing figure. 



Common Gull. 



The terns take up the succession from the gulls ; 

 and, in the gull-billed tern, which may be considered 

 as the commencement, there is much similarity, not 

 only in that organ, but in the general air of the body; 

 and as we trace them to the more typical terns, the 

 bill does not assimilate to that of the swallows (though 

 the terns have — not very discerningly — been called 

 " sea-swallows "), but to that of the pratincole, which 

 may perhaps be considered as the last of the 

 omnivorous feeders among the land-birds, and the 

 most powerful on the wing. And it is not a little 

 remarkable, that when this rare but beautiful strsnger 

 makes a dash over from the Danube to the Hebrides 

 or Zetland, by way of a morning trip, it is found in 

 the company of gulls and terns. 



The storm-petrels are the real swallows of the sea 

 — the birds which feed upon the lightest and highest 

 production of the waters just as the swallows and 



