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THE BIRD ROOKERIES OF THE TORTUGAS. 



By PAUL BAETSCH, 

 Curator, Marine Invertebrates, U. S. National Museum. 



[With 38 plates.] 



Look at a map of the southeastern United States and you will note 

 a string of islands swinging south, then bending more and more 

 westward at some little distance off the peninsula of southern Florida. 

 These are the Florida Keys, a part of which in reality represents an 

 ancient barrier reef long since elevated above the surface of the sea. 

 Some of these keys are mere barren sand banks, while others are 

 clothed with tropical vegetation. Quite a number of these islands 

 have recently been joined by the fills and viaducts of the over-sea por- 

 tion of the Florida East Coast Railway which connects Key West 

 with the mainland, and promises to produce profound changes in the 

 topography of the region. This chain of keys terminates in the Tor- 

 tugas Atoll, the scene of our story, some 65 statute miles west of 

 Key West. 



The elevated portions of the atoll at present are East, Middle, and 

 Sand Key, of the middle eastern perimeter ; Long, Bush, Bird, Garden 

 Key of the southwestern rim ; and Loggerhead Key on the southwes- 

 tern border. Formerly two other keys, Northeast Key and North 

 Key, of the northeastern edge, were conspicuous elevated elements 

 above the sea's surface, but they have long since been swept away 

 by the waves. Of the existing keys, Middle and Sand Key are mere 

 heaps of piled up sea organisms and their fragments, without vege- 

 tation. Bush Key now appears as an elevated coral reef with piles 

 of organic detritus heaped up in spots, but likewise barren of vege- 

 tation. East Key supports a dense growth of Bermuda grass on the 

 flattened, upper elevated portion, with a scattered growth of scaevola 

 bushes and other plants. A somewhat similar condition obtains 

 on the southern end of Long Key, but the vegetation is less abundant 

 and more scattered, while the northern end consists of a barren rim 

 of coral boulders that curves eastward and southward, to join with 

 the reef fringe of Bush Key. Garden Key is almost completely in- 

 closed by the walls of Fort Jefferson. The portion outside of the 

 wall is overgrown with crab grass and the long trailing vines of the 

 65133 SM 1917 31 469 



