22 Vol. XXIV 
SOME BIRDS OF ROOSEVELT LAKE, ARIZONA 
By HARTLEY H. T. JACKSON 
WITH MAP AND ONE PHOTO 
HE NOTES on the birds of Roosevelt Lake, Arizona, here presented are 
intended only as supplementary to the interesting account by Swarth!, 
and include remarks only on those species found within the area actually 
covered by the lake proper and its immediate shore-line. The investigations 
were undertaken for the U. S. Biological Survey as a part of its general study 
of the land vertebrates of the state. Field work was conducted at the northern 
end of the lake May 19-24, 1916, although actual observations of the water 
birds were made mostly on May 20 and 22, and a trip was made by motor- 
launch to the bird colonies at the eastern end on May 26. Swarth visited the 
colonies of cormorants and herons on the lake early in June, 1917, a little more 
than a year after my observations were made; but the time he had available 
for study of the water birds was less than in my own ease, and this in part 
probably accounts for the apparently greater number, both of individuals and 
Species, indicated in my list. The counts of the breeding birds were made 
after I had become fairly well acquainted with the colonies, and I believe they 
are reasonably accurate. They are based on actual counts of adult birds, 
checked with counts of the nests. 
Roosevelt Lake, which is formed by the damming of Salt River by Roose- 
velt Dam, is located near the geographical center of Arizona at an altitude of 
2300 feet. It hes in a general southeasterly-northwesterly direction, is about 
thirty miles long and three miles wide in its widest part, and has a very irreg- 
ular shoreline, particularly on the northern side. The lake is about 275 feet 
deep in the deepest parts, the supporting dam being 286 feet high. The water 
in this reservoir is supplied mainly by two streams, Salt River, which flows in 
from the east, and Tonto Creek, which flows in from the north, at opposite 
ends of the lake. The former banks of both Tonto Creek and Salt River were 
lined with cottonwoods (Populus wizlizeni), and in the shallow water near 
the ends of the lake many of these trees, killed by the high water, have their 
tops left protruding from the surface of the lake, offering nesting sites for 
cormorants and herons. Farther up these streams, particularly up the Tonto, 
are dead small trees and bushes, and large iive trees, the trunks of which are 
but little submerged, where other herons nest. Both of these streams carry 
quantities of debris and silt, and already a mud and sand flat has begun to 
form at each end of the lake, especially noticeable at the Tonto end. Salt 
River seems to carry more debris, such as timber, but less silt. The flat at 
the mouth of the Tonto covers an area of approximately four square miles. At 
present there is no marsh or perceptible amount of aquatic vegetation growing 
on these flats, but it is possible, though hardly probable, that ultimately such 
a type of vegetation may develop, adding increased nesting places for species 
of birds now unknown to breed on the lake. The variation in the water level, 
however, tends to prevent the growth of such vegetation. Except at the ex- 
d ) ; e Papago Saguaro National Monument and the neighbor- 
ae Zeer Ra a published by the National Park Service, Dept. of Interior, Washing- 
