GEOGRAPHY OF CENTRAL FLORIDA 229 



itudes 27° and 30°. (The other species of Aphelocoma, eight or 

 nine in number, are all western, ranging from Texas and Idaho to 

 Central America.) 



The dusky seaside sparrow {Passerherbulus nigresccns), al- 

 though described as long ago as 1873, is still known only from 

 marshes within a few miles of Titusville on the east coast. Chap- 

 man says of it (Handbook, p. 394) : "In view of the fact that 

 this species is abundant and that the region is in no sense isolated, 

 but that both to the north and south there are marshes apparently 

 similar to those it occupies, the restriction of its range to an area 

 only a few square miles in extent makes its distribution unique 

 among North American birds." 



Besides these well-marked local species of non-migratory birds 

 there are several other cases in which the Florida birds differ just 

 a little from those of the -same species farther north, as stated a 

 few pages back, but it is hardly worth while to mention them in 

 a work of this kind. 



Among extinct birds there is one noteworthy record, the find- 

 ing of bones identified as belonging to the great auk (Plant us iin- 

 pennis) in a shell mound near Ormond by Prof. Blatchley in 1902. 

 This penguin-like bird was chiefly confined to the colder parts of 

 the Atlantic ocean, and there is no record of its having been seen 

 alive since 1842. 



One avian product that deserves special mention is bird guano. 

 The principal source of this has been a few small islands off the 

 coast of Peru, where myriads of sea birds have roosted and nested 

 for ages, safe from most of their enemies, and where rain is prac- 

 tically unknown, so that there is no leaching of the valuable fer- 

 tilizing constituents of the guano. The deposits have been ex- 

 ploited more or less for centuries, but the industry reached its 

 height in the third quarter of the last century.* 



In recent years some artificial guano islands have been con- 

 structed near Cedar Keys, by building w^ooden platforms a few 

 feet above the shallow waters of J;he Gulf a few miles off shore. 



*Probably the most accessible descriptions of the guano islands of Peru 

 are those by Dr. Robert E. Coker in the Proceedings of the U. S. National 

 Museum 56:449-511, pi. 53-69 (Sept. 1919), and in the National Geographic 

 Magazine 37:537-566, with 28 unnumbered half-tones (June, 1920). 



