30 LIFE HISTORIES OF NORTH AMERICAN DIVING BIRDS 



were close together, and were intimately mingled with the gulls' nests. Per- 

 haps because they had drifted, some of them rested directly against gulls' nests, 

 but they had not been abandoned. The nests were partially submerged plat- 

 forms of green vegetation pulled up from the bottom and were without even 

 as much form and stability as is usually possessed by the rude structure of 

 the pied-billed. The eggs were half under water, and it seemed a marvel how 

 they stayed on the loose platforms at all. They were only imperfectly covered. 

 These grebes, unlike their pied-billed relatives, stayed close by their nests and 

 for the most part on them. When driven off they all swam rapidly away in 

 a body and circled around at a safe distance, only to return immediately as 

 soon as the coast was clear. In clambering up onto these frail nests they 

 tipped and nearly sank the whole affair, but it nevertheless afforded sufficient 

 support for them to lie for hours basking in the sun, often on one side, with 

 the head held awkwardly up, and one leg waving clear of the water a curious 

 attitude, which it took us some little time to make out in detail with the 

 aid of our glasses. 



Eggs. The American eared grebe lays from 3 to 9 eggs and raises 

 but one brood in a season; the usual set consists of 4 or 5 eggs and 

 the larger numbers are proportionately rare or perhaps the work of 

 more than one bird. The eggs are absolutely indistinguishable from 

 those of either the horned grebe or the pied-billed grebe ; there is no 

 constant difference in size, shape, or color. The shape is usually 

 "ovate" or "elliptical ovate," but some eggs are more elongated to 

 "elongate ovate" or nearly "fusiform." The ground color, when 

 first laid, is bluish or greenish white, but it soon becomes perma- 

 nently stained, from contact with the nest, until the eggs show a 

 variety of shades of buff or brown colors, which will not wash off. 

 The eggs are often more or less covered with mud or bits of vegetable 

 matter, which can be removed by washing. The measurements of 

 55 eggs, in the United States National Museum, average 43.5 by 30 

 millimeters; the eggs showing the four extremes measures 47 by 30.5, 

 45.5 by 32, 39 by 29, and 43 by 27.5 millimeters. 



Morris (1903) gives the period of incubation as about three weeks 

 for the European bird and Yarrell (1871) says that both sexes incu- 

 bate; probably either of these statements would apply equally well 

 to the American bird. Much discussion has arisen over the question 

 whether grebes incubate their eggs or leave them to hatch from the 

 heat generated by decaying vegetation in the nest or by the warmth 

 of the sun's rays. It seems hardly likely that sufficient heat could 

 come from the decaying vegetation in the nest, as the nests are always 

 wet and the water in which they are built is usually cold during the 

 nesting season; I have never been able to detect any appreciable 

 warmth in the nesting material and have often noticed that the eggs 

 were warm on top, as if they had recently been left by a sitting bird, 

 and cold on the under side where they came in contact with the 

 wet nest; the reverse would be true, if the nest supplied the heat. 

 Grebes, particularly of this species, have frequently been seen incu- 



