128 BlCKNELL on the Carolinian Fauna 



Woodpecker fly from a hole in its side about twenty feet from the 

 ground. On shaking the stub I could distinctly hear young birds within, 

 which greatly snrj trised me, for many of them are not yet breeding, as shown 

 by the size of their ovaries. The parent bird immediately returned, 

 flying about overhead, and sometimes alighted on the stub, uttering, every 

 now and then, her characteristic ker-r-r-ruck, ker-ruck-ruck-ruck. 



EVIDENCES OF THE CAROLINIAN FAUNA IN THE LOWER 

 HUDSON VALLEY. PRINCIPALLY FROM OBSERVATIONS 

 TAKEN AT RIVERDALE, N. Y. 



BY EUGENE P. BlCKNELL. 



The restrictionary causes circumscribing geographical divisions of 

 animal and vegetable life, though as yet but imperfectly under- 

 stood, are well known to bear little relation to absolute latitudinal 

 parallels, but to be largely independent of these equidistant surface 

 divisions, and likewise to a certain extent unconformable with iso- 

 thermal lines. The boundaries of faunal areas are usually of an 

 extremely irregular nature, and in their territorial relations con- 

 tiguous fauna) often present a series of mutual interpenetrations, 

 the apparent invasion by one province of an adjoining district of 

 course being coincident with an opposite extension or penetration 

 of the invaded territory. 



Thus from near the northeastern boimdary of the Carolinian 

 Fauna two main branches emanate, — one striking up into the valley 

 of the Hudson ; the other extending along the Connecticut coast 

 and into the Connecticut valley, through which reaching the Mas- 

 sachusetts border.* The relations between these two tributaries 

 at their junction with the main body of the fauna to which they 

 belong, or their consolidation before reaching that point, is at pres- 

 ent but very superficially understood ; but from what knowledge 

 we have in the matter it would appear that their interception 

 occurred somewhere near the mouth of the Hudson, thus includ- 

 ing New York City and vicinity in the angle formed by their 

 divergence. 



The northern limit of the HudBon River branch is as yet unde- 



* A Review of the Birds of Connecticut. By C. Hart Murium, p. 1, 1877. 



