90 
ALTRICIAL GrRALLATORES — HERODIONES. 
blackish. Young: Uniform, rather dark, grayish brown, the rump, upper tail-coverts, basal half 
of tail, and entire lower parts, including axillars and lining of the wing, continuous white ; head 
and neck streaked with dusky or grayish brown on a grayish or dull whitish ground-color. 
Feathering of the head extending forward almost to the bill. 1 
Length, about 24.00-26.00 ; expanse, about 40.00 ; wing, 10.30-11.75; tail, 4.00-5.00 ; culmen, 
4.15-6.30 ; depth of bill, .60-.72 ; tarsus, 3.10-4.00 ; middle toe, 2.15-2.70 ; bare portion of tibia, 
2.00-2.80. 
In this species there is a range of individual variation not exceeded by any member of the 
family ; this variation affecting not only size and relative proportions of the different parts, but 
also characters which have been accorded generic or subgeneric value. Thus, taking two perfectly 
adult birds from localities geographically near together (Mazatlan and Tehuantepec, Western and 
Southwestern Mexico), they represent very nearly, if not quite, the extremes of size, especially 
as regards the bill ; one of them (No. 58816, Mazatlan) having this member 6.30 inches in length, 
while in the other (No. 59773, 9 . Tehuantepec) it measures only 4.70. As to colors, they are 
identical, both being pure white, with the terminal portion of the four outer primaries glossy 
greenish-black. There is a most remarkable difference, however, between these two examples in 
the anterior outline of the feathering of the head, which difference may be explained as follows : 
In the Mazatlan specimen the frontal apex all but comes in contact with the base of the culmen, 
there being left between a space only about .05 of an inch wide ; in the Tehuantepec specimen there 
is an interval left of .80 of an inch ! In the Mazatlan example, the anterior feathers of the throat 
form a broad angle projecting forward into the bare gular skin for a distance of .60 of an inch ; in 
the Tehuantepec specimen, their anterior outline has exactly the opposite form, being regularly and 
deeply concave, so that the bare gular skin has a semicircular or regularly convex posterior outline — 
exactly as in fully adult specimens of E. ruber ! In the former of these specimens the malar 
feathers extend forward to within .25 of an inch of the rictus, or to much beyond the anterior 
angle of the eye ; while in the other they approach to within only about .70 of the rictus, scarcely 
reaching to below the middle of the eyes. 
Other characters in which the Tehuantepec example differs from the one from Mazatlan, consist 
in the subterminal portion of the bill being black for the space of nearly two inches, and in the 
distinct serration of the middle portion of the tomia. These extremes of variation are noticeable 
among skins obtained during the breeding season in Florida, specimens from the same breeding 
grounds differing as much as the two described above. 
Immature specimens show, according to age, all possible stages of plumage intermediate be- 
tween the pure white adult and gray young. 
The White Ibis is a resident only in the more southern portions of the United 
States, though it not unfrequently occurs as a straggler in various places farther 
1 According to Audubon, “the young birds are at first covered with thick down of a dark gray 
color.” 
