LIFE HISTOKIES OF NORTH AMERICAN DIVING BIRDS. 37 



4 to 6 inches in height and from 14 to 24 inches in diameter at the base, tapering 

 to 6 or S inches at the top, and they were liberally plastered with mud, especially 

 the depression which held the eggs. The area of this depression, the depth of 

 which is about 1 inch, is determined by the number of eggs in the clutch, as they 

 fit snugly into it. 



Of five nests located from June 25 to July 9 two contained 4 eggs and three 

 3 eggs. All these sets were from slight to heavily incubated. The eggs were 

 badly stained, and the majority retained a rich brown cast even after the most 

 vigorous scrubbing. In all cases the eggs were covered by a thin layer of damp, 

 decayed reeds. 



We were unable to flush the bird from any of these nests and were able to 

 identify them only by patient and lengthy waiting. These grebes are very hard 

 to see on this lake, as they keep close to the reeds, and if found a short dis- 

 tance from them they immediately slip under the water and disappear. How- 

 ever, they were seen feeding in the company of American eared grebes, Florida 

 gallinules, and American coots. 



Eggs. — The breeding season for the Mexican grebe is so prolonged, 

 from April to December, that it seems likely that two or three broods 

 may be raised in a season. This habit is decidedly exceptional 

 among water birds, although there is some evidence to indicate that 

 the pied-billed grebe may raise two broods in a season. The Mexi- 

 can grebe lays from three to six eggs, usually four or five. In shape 

 the eggs vary from " elliptical oval " to " oval," with a tendency to 

 become " fusiform " or more or less bluntly pointed at both ends. 

 The shell is fairly smooth and quite glossy. The color is said to be 

 bluish white or dull buffy white, but all that I have seen are so badly 

 nest stained that the original color is no longer visible. The eggs 

 in my collection vary from " cinnamon buff " to " cream buff," with 

 numerous darker stains and specks of dirt. The measurements of 

 49 eggs in the United States National Museum and the author's 

 collections average 33.9 by 23.4 millimeters; the eggs showing the 

 four extremes measure 38 by 24, 35 by 25, 30 by 22.5, and 32.5 by 23 

 millimeters. 



Plumages. — The downy young when first hatched is "blackish 

 brown " above, which fades to " olive brown " in older birds ; there 

 are three narrow, broken, longitudinal white stripes on each side of 

 the back, which disappear in older birds; the head and neck are 

 broadly and irregularly striped with black and white; the crown is 

 mostl}'' black with a triangular or V-shaped rufous patch in the cen- 

 ter ; the belly is white. This downy covering is not replaced by the 

 first real plumage until the young bird is fully grown, when the first 

 winter plumage is acquired. Young birds can then be distinguished 

 by their smaller bills ; the head is leaden gray, with a darker crown 

 and a whitish throat ; the neck and chest are brownish or dusky and 

 the sides are dusky. During the following spring, when the young 

 bird is nearly a year old, it assumes a plumage which is practically 

 adult. I have seen young birds undergoing this molt in May. 



