95 
Mr Edmondston on the Kittiwake^ ^c. 
rings, in their passage southward, swarm on the coasts of Zet- 
land, numerous flocks of these three species of gull, in all pos- 
sible stages of plumage, are found attending them. Many of 
these are in mature plumage, but are never obser\ed to frequent 
the clilfs where their species l^reed, and are therefore also called 
Yeeld. I have opened a few of them, and their sexual appear- 
ances were very imperfect. 
At a particular time of the tide the herrings descend from the 
surface, and, during the interval of their absence, these gulls 
generally repair inland, and rest amongst the heaths. As soon, 
however, as the tide changes, and the herrings again rise, they 
tumultuously quit their retreats, and, by their wild and discord- 
ant screams, express to each other the anticipated joy of their 
approaching feast. When they take wing, it is a sign that the 
period of fishing is at hand. I have often been astonished at 
the precision and regularity with which flocks, far removed from 
the view of the sea, seemed, from a state of tranquillity and re- 
pose, suddenly to display bustle and activity, and instantly bend 
their course to the fishing-ground. This has been supposed to 
depend on a certain change of the air, coincident with the change 
of tide, which, though not cognisable by our senses, may be evi- 
dent to theirs : but such a change and such sensations seem quite 
hypothetical. I should more simply account for it on the sup- 
position that other individuals of their own species, engaged in 
the same pursuit, and nearer the fishing-ground, had by their 
sounds or movements given them notice of what was going on. 
Young birds, therefore, often differ from adult birds, not less 
in habits than in plumage, and often, when perfectly agreeing 
in the one, they essentially differ in the other; — ^remarks which, 
though sufficiently simple, and obviously useful, have been too 
frequently lost sight of in ornithological discussion. 
The kittiwake, from its number and familiarity, affords also 
an excellent example for studying the general habits of gregari- 
ous and migratory birds. One remark, its history well illustrates, 
which, I believe, apphes to all the larger and more regular mi- 
gratory birds, that they not only return annually to the situa- 
tions appropriated by their species for incubation, but also that 
only certain tribes of their species occupy certain parts of these 
situations, and that this right of property, as it were, is respected 
