20 



Mackay, Habits of the Double-crested Cormorant. \ \\n 



rectly shown and located under the name of the 'Cormorant 

 Rocks.' It would not, therefore, seem unreasonable to infer that 

 they were so named on account of being frequented by these 

 birds at that early period, or even before. If such a conclusion 

 is admissible it would show an occupancy of certainly one hun- 

 dred and sixteen years, and possibly for a longer period, as well 

 known local names are preserved when feasible in order to avoid 

 confusion. There is, however, other evidence of long occupancy 

 of still greater interest to the ornithologists, in the fact that I 

 discovered, on careful examination, that many of the projections 

 of the rock on the mesa top, which afforded good sta?iding 

 places, had apparently been worn smooth and glossy by long 

 use. These resting places sloped down on the sides, afford- 

 ing the birds, when standing on them, convenient places for 

 ejecting their excrement, there being invariably a deeper deposit 

 of lime at their base than on other portions of the mesa top, 

 which was also covered with such deposit to a greater or less 

 degree. 



On the flat top of the rock I found and saw a large number of 

 curious balls (and brought fourteen away with me) varying from 

 an inch to two inches in diameter and composed almost entirely 

 offish bones, chiefly the bones of young parrot-fishes (Labroids) 

 and drums (Sciamoids) 1 firmly cemented together with gluten, 

 hard in the dried specimens and soft and gelatinous in those more 

 recent. One of the largest of the former, which was rive and a 

 quarter inches in circumference and quite black, while all the 

 others were of a light color, contained three crabs ( Cancer 

 irroratus Say = Panopeus sayi Smith) in a fairly perfect con- 

 dition, with some of the claws still remaining in place, showing 

 they were probably swallowed whole. I am consequently in- 

 clined to the opinion, in the absence of absolute facts, that these 

 birds, like the Owls, have the power of ejecting indigestible 

 substances. 



The Cormorant Rocks are of small area, the mesa top being 

 only about thirty or forty feet square (estimated), the greater 

 part of which is covered with a deposit of lime, its depth varying 



■ 'I am indebted to Mr. Samuel Henshaw of the Boston Society of Natural History, 

 and to Mr. Samuel Garman and Mr. Walter Faxon of the Museum of Comparative 

 Zoology, Cambridge, for aid in identifying the composition of these balls. 



