2 crocodilians. Among the turtles, 

 the most common are the striped mud 

 turtle and the Florida box turtle. 

 Lizards are most commonly repre- 

 sented by the green anole and the 

 skinks. More common and ubiquitious 

 snakes include the Florida brown 

 snake, the eastern garter snake, the 

 peninsula ribbon snake, and the rat 

 snake. By far the most conspicuous 

 reptile is the alligator. 



McDiarmid (1978) lists the al- 

 ligator ( Alligator mississippiensis ) 

 and the Eastern Indigo snake ( Dry- 

 marchon corais cuperi ) as species 

 "of special concern". The American 

 crocodile ( Crocodylus acutus ) whose 

 numbers are estimated to be only 

 200-500, and whose observed range is 

 limited to upper Florida Bay and 

 lower Taylor Slough is listed as 

 endangered. More information on 

 the crocodile is presented in Chap- 

 ter 7.34. 



6.25 BIRDS 



Of those vertebrates for which 

 a species list is presented (Table 

 27), birds are by far the most num- 

 erous wildlife group. Two hundred 

 and twenty-one (221) species are 

 listed as utilizing the 7 habitats 

 of the terrestrial and freshwater 

 glades (SFRC 1980). Around 60% of 

 the bird species reported regularly 

 from the south Florida area are win- 

 ter residents or migrating visitors 

 (Robertson and Kushlan 1974). Thus, 

 species diversity and population 

 densities increase in the winter. 



In general terms, the avifauna 

 is composed of two major groups, the 

 water birds and the land birds 

 (Robertson and Kushlan 1974). Water 

 birds in turn may be subdivided into 

 three categories: seabirds, species 

 of estuarine and coastal wetlands, 

 and species of interior wetlands. 

 The first two of these subdivisions 



are obviously of less relevance in 

 this section than the species of 

 interior wetlands birds and the land 

 birds. However, while none of the 8 

 primarily oceanic birds occurring 

 off of south Florida are reported in 

 the freshwater wetlands, many of the 

 coastal and estuarine species do 

 frequent the interior wetlands as 

 well. 



A primary characteristic of the 

 interior wetland avifauna of the 

 lower Everglades is its relative 

 impoverishment of breeding species 

 compared to the nearby West Indies 

 (Robertson 1955, Robertson and 

 Kushlan 1974). Whereas 15 breeding 

 species of interior wetlands birds 

 are reported from the Everglades, 26 

 species are reported from Cuba. 

 With regard to breeding land birds, 

 the lower Everglades is also rela- 

 tively impoverished, exhibiting only 

 30 to 35 species compared to 60 to 

 70 species farther north in the 

 state. This trend is especially 



pronounced with respect to the pas- 

 serine birds, while the number of 

 nonpasserine species compares fairly 

 well to other locations within the 

 same latitude. 



Robertson and Kushlan (1974) 

 offer two reasons for the avifaunal 

 impoverishment of interior wetlands 

 birds, one historical and one ecolo- 

 gical. The historical reason focus- 

 es on the relative geological youth 

 of the interior wetlands environment 

 compared to other West Indian is- 

 lands. Five thousand years ago, 

 only a mini-Everglades environment 

 existed along the fringes of Florida 

 Bay and the southwest coast. Much 

 of the area was considerably drier 

 during the earlier Wisconsin period 

 of the late Pleistocene. Thus there 

 was, historically speaking, little 

 wetland habitat available in south 

 Florida at that time. The ecolo- 

 gical reasoning follows from the 



137 



