Mar., 1922 ROOSTING HOLES OF THE RED-SHAFTED FLICKER 57 
/. Three and one-quarter by three and one-half inches. This opening is in 
the upper corner of the building, within the angle formed by the corner board 
and the trimming beneath the roof. The bird using this hole roosts on a two 
by three inch board forty inches below the hole, as is evidenced by the accum- 
ulation of droppings along this board and on the floor directly below. 
g. Three and one-quarter by four inches. Between the angle formed by 
the juncture of the corner-board and the cornice, a similar position to c, on the 
opposite side of the building. Here a drop of forty-two inches is required to 
reach the same supporting boards to which more direct access is secured by 
making entrance through holes d and e. 
Observation of these holes discloses the fact that the bird prefers, or more 
probably requires, a projection or some other foothold to which it may chung 
while chipping out a hole in a flat surface such as the side of a building. HEaen 
of the holes, as well as the incompleted ones not sketched, are drilled close 
against a board used as trimming (shown in the sketch by heavier shading) 
which furnishes a support to the prospective lodger. The broken lines drawn 
through the figures to show location of the joints between the boards would 
indicate that operations are commenced along this juncture, apparently for 
the reason that the erack facilitates the beginning of the project, though the 
boards are tongued and grooved and fit snugly together. | | 
Bemcwa, Califorma, January 12, 1922. 
A LAW GOVERNING THE ELEVATION OF THE NESTING SITE 
By CHARLES KETCHUM AVERILL 
N Chapman’s ‘‘ Warblers of North America’’ particular attention is given 
to the vertical range in the trees of the arboreal species in their summer 
homes. Thus, the Cape May ‘‘lives in the tops of high coniferous trees’’. 
The Blackburn ‘‘is a lover of deep mixed growths and the upper branches of 
the biggest conifers’’. Other species of the same genus, Dendroica, are more 
lowly in range. The Prairie Warbler keeps near the ground. Of the Chest- 
nut-sided we note that ‘‘its beat les between the ground and the tops of small 
deciduous trees’’. In this way we may note the habit of each species and 
make a list of those that are high ranging and another of those that range low. 
From the same source we may learn the nesting height of each species. 
and place this informaticn opposite each. In the Auk (vol. 37, October, 1920, 
p. 572) IJ called attention to the fact that as length of wine is a factor in ease 
and power of flight, and the tail an impediment to flight, the bird with the 
longer wing and shorter tail might be called the better flier, and species so 
proportioned were the ones making the longer migrations. Taking the wing 
and tail lengths from Rideway’s ‘“‘Birds of North and Middle America’’, the 
figures being the average given for the male bird in every case. and subtract- 
ing the latter from the former we may complete the table of the genus Dew- 
droica by placing the wing and tail difference in a third column. 
