128 
Bicknell 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 surprised 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. BICKNELL. 
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 uncomformable with iso- 
thermal lines. The boundaries of faunal areas are usually of an 
extremely irregular nature, and in their territorial relations con- 
tiguous faunae often present a series of mutual intprpenetrations, 
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 boundary 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 Hudson River branch is as yet unde- 
* A Review of the Birds of Connecticut. By C. Hart Merriam, p. 1, 1877. 
