56 



The Canadian Field- Naturalist 



[Vol. XXXIII 



water birds, we found the different species keeping 

 pretty well to themselves. The Caspian Tern sel- 

 ected for itself the highest portions of the island, 

 namely, the tops of the two knolls. Here they rested 

 when they came in from flight, and the fact that 

 they always seemed to prefer to rest on the highest 

 point probably accounts for the small number of 

 nests on that part of the knoll. There were only 

 five nests on top of the large knoll. On the sides 

 were more nests of the Caspian Tern, but as the 

 lower level was approached the nests of the Ring- 

 billed Gull began to be found, and when the level 

 at the bottom of the slope was reached, no more 

 Caspians were to be seen. In addition to the five 

 nests of the Caspian found on top of the large 

 knoll, there were ninety-three nests on the sides of 

 it. On the smaller knoll we found fifty-seven nests, 

 making one hundred and fifty-five with eggs in all. 

 It is to be presumed, therefore, that this colony con- 

 sists of about 350 or 400 breeding birds, as many 

 of the sets were incomplete and some of them had 

 probably not yet begun to lay. 



The habit of Terns in general is to make a very 

 sketchy nest, often nothing more than a mere hollow, 

 and the nests of the Caspian on top of the knoll 

 followed this general rule, but as one observed the 

 nests on the sides of the knoll, he found that as he 

 went down the side, the nesls became more and 

 more substantial, until the bottom nests were almost 

 as elaborate as those of the Ring-billed Gulls nest- 

 ing alongside, and our surmise was that the higher 

 levels were the preferred nesting ground for all 

 species, and that the ring-bills started to lay iheir 

 eggs on these higher levels but were ousted from 

 them by the Caspians who adopted the more sub- 

 stantial nests of the gulls. The Caspians which 

 were later in beginning to lay would then steal 

 the nests of the next highest Ring-bills. This theory 

 would account for the increasing thickness of the 

 walls and lining of the Caspian nests as the lower 

 levels were approached and the fact that the Cas- 

 pians and the Ring-bills were nesting vv^thin three 

 or four feet of each other in some places, also sup- 

 ports the theory. At one point at the south-east side 

 of the larger knoll there was a clump of small bushes, 

 in and around which were five nests. Three of these 

 were Caspians and two were Rmg-bills, one of 

 these being in the centre of the patch. 



It was very interesting to have these birds so 

 close together and to compare their voices. The 

 notes of the Caspian are, of course, unique and no 

 one who has ever heard •hem would think of con- 

 founding them with any other kind of water bird 

 to be found in Ontario. One does not need an ear 

 for music to accomplish the distinction. Any one 

 who can tell the bray of a donkey from the rooster's 



crow, should be able to distinguish the Caspian Tern 

 by its notes, but the Herring Gull and the Ring-bill 

 have long been a puzzle to me and I did not get 

 any serious help from this visit, except that the Ring- 

 bill did not give us any example of the cackle so 

 often used by the Herring Gull, but the musical 

 tones of the gulls we found indistinguishable, both 

 of them using many different pitches and phrasings. 

 Considering that there was so little opportunity 

 for concealment, the Ring-billed Gulls concealed 

 their nests very well, placing them among the 

 grasses which grew in the cracks between the rocks. 

 When the cracks were of sufficient dimensions, 

 say five or ten inches, the concealment thereby af- 

 forded was substantial, and the Ring-billed Gulls 

 placed their nests in these strips of grassy growth at 

 from four or five feet to fifteen feet apart. 



We found the Herring Gulls to be less compan- 

 ionable than the others as their nests were much 

 farther apart, seldom being as close as fifteen feet 

 from one another. They seemed also to have laid 

 their eggs a little earlier as we found three or four 

 of their nests with newly hatched young, while none 

 of the Ring-bills or Caspian Terns had hatched a 

 single egg. Three was the maximum set for each 

 and two were apparently being incubated in a good 

 many cases. 



Against the 1 55 nests of the Caspian Tern we 

 found only 64 nests of the Herring Gull, and 77 

 nests of the Ring-billed Gull, and Mr. Bottril and 

 Mr. Brown think that the Caspians in the colony 

 are increasing slowly. 



Sometimes nesting grounds of this character are 

 apt to be much molested by human beings, but in the 

 present instance such is not the case. 



During the nesting season, the Georgian Bay in- 

 dulges in a good deal of windy weather. The ap- 

 proach to these islands is so bad that landing can 

 only be managed on a day so calm that it would 

 be exceptional. To make matters still better for the 

 Gulls and Terns they nest in a season in which the 

 fishermen are very busy, and there is no other class 

 of inhabitants nearby. 



One of our friends had heard that there were 

 a few Caspian Terns nesting on an island some ten 

 or twenty miles south where the Common Tern has 

 a colony, but we were not able to investigate this 

 rumor. 



The migration route of this species was for a long 

 time an unsolved puzzle. They appeared in small 

 numbers at various points in the lower lakes and 

 that was about all we knew of them, but from the 

 observations of Mr. E. M. S. Dale of the Mc- 

 Ilwraith Ornithological Club, and of our president, 

 Mr. J. F. Calvert, it seems that after the breeding 

 season has finished, these birds make a very leisurely 



