BIRD EOOKERIES OF TORTUGAS BARTSCH. 473 



seen fishing as they are wont to do in the Tortugas, or resting on float- 

 ing driftwood, sand beaches, or low, rocky ledges, but in March or 

 April (the time seems to vary in different years, as shown by the 

 table below) the homing instinct seizes them and they head for their 

 favorite island of the Tortugas group. 



Table shmcing dates of arrival and departure. 



Data furnished by the Biological Survey, TJ. S. Department of Agriculture, whose warden protects the 

 colony from eggers.) 



Watson and Lashley, in speaking of the Bird Key rookery, 1915, 



page 61, say: 



The terns breed in great numbers upon Bird Key. * * * Their nests, of 

 which there were more than 10,000 in 1908, are in many cases closely crowded 

 together, as many as 30 sooty nests being found in an area of 100 square feet, and 

 the nests and eggs are almost indistinguishable to the human observer. Indeed, 

 the island suggests a city of 10,000 houses, all much alike, unnumbered, and set 

 down at random, without streets or definite landmarks. The birds choose their 

 own nests, without error, from among hundreds of similar ones, and under 

 normal conditions never show the slightest hesitation in making their choice. 



I will now consider, one by one, the various species in the order of 

 their numerical representation. I shall use freely the data furnished 

 by Audubon. Watson, and Lashley in the discussion of the various 

 forms. 



THE SOOTY TERN (Onychoprion fuscatus). 



By far the largest number of breeding birds on the Tortugas belong 

 to this species, of which probably more than 25,000 are present on 

 Bird Key at the close of the breeding season. 



Our earliest record of this colony was furnished by that master of 

 ornithological biography, John James Audubon. 1 The description 

 which he gives us of the colony, based upon a visit during the early 

 part of the last century, is extremely interesting. The rareness and in- 

 accessibility of the volume demands a full quotation in order that an 

 adequate comparison may be had with the now existing conditions. 

 We therefore quote the following: 



Early in the afternoon of the 9th of May, 1832, I was standing on the deck of 

 the United States revenue-cutter the Marion. The weather was very beautiful, 



1 Ornithological Biography, vol. 3, pp. 263-269. 1835. 



