GEOGRAPHY OF CENTRAL FLORIDA llj 



North America. (If only nesting- birds are counted we have about 

 one-fourth.) The exact number is and always will be indeter- 

 minate, on account of differences of opinion as to what constitutes 

 a species, if nothing else.f Another reason is that there are quite 

 a number of birds that feed in the ocean near by but rarely if ever 

 nest on our coasts, or which pass over in their annual migrations 

 between North and South America and seldom stop, and some 

 whose usual migration routes lie considerably to the eastward or 

 westward but are occasionally blown out of their course by storms 

 and forced to land. Then too there must be many which barely 

 reach our limits from the north or south, and whose ranges are 

 not yet known with sufficient exactness to indicate whether they 

 occur within the arbitrary limits of this work or not. But all these 

 uncertainties should not materially affect the statistical observa- 

 tions which follow. 



The birds of North America are divided into two great groups : 

 water birds, comprising (according to Chapman) 9 orders and 29 

 families, and land birds, with 8 orders and ^^7 families. The for- 

 mer are the more ancient and primitive types, and seem to be most 

 characteristic of regions that are geologically young, while the lat- 

 ter have evolved so recently that there are comparatively few fos- 

 sil records of them, and they are most abundant in regions that 

 have been dry land for ages. About 467© of the birds (species, 

 not individuals) in central Florida are water birds, as compared 

 with 42% in eastern North America, 38% in the whole United 

 States and Canada, and only 10 or 12% in the whole world.* But 

 the water birds as a rule have wider ranges or migrate more than 

 the land birds, so that even if other things were equal they should 



JAs there are more bird students than species of birds in civilized countries, 

 the temptation is -strong to keep drawing finer distinctions, making slight dif- 

 ferences the basis of subspecies, and elevating subspecies to the rank of species 

 from time to time. Birds of widely distributed species that do not migrate much 

 are apt to be a little smaller and darker in Florida than farther north, and 

 already quite a number have been separated for that reason, and doubtless 

 mo>re will be hereafter. Some of the mammals show the same sort of vari- 

 ation, as was pointed out by Dr. Allen in the paper previously cited. 



• *This high percentage of water birds in new lands seems analogous to 

 the high percentage of monocotyledons among flowering plants in the same 

 areas. See a statistical method for comparing the age of different floras, 

 in Torreya for December, 1905. Also 3d Ann. Rep. Fla. Geol. Surv., p. 357. 



