The Behavior of Noddy and Sooty Terns. 197 



tainty be answered at present.^ On account of this utilization of the old 

 nest from j-ear to year, some of the oldest nests have grown to enormous size, 

 due to the addition of new materials at each successive season. 



The photograph of the group of nesting noddies (fig. 22, plate 8) shows 

 the tallest of the bay-cedars (about 12 feet) and what I judge to be some 

 of the oldest nests. Figure 5, plate 2, shows a newly constructed nest, which 

 is much smaller. 



The statement has been made that the noddy sometimes lays its eggs 

 directly upon the ground, but this is not quite true for noddies on Bird 

 Key.- Very often the nest has the appearance of being constructed directly 

 upon the ground, but a closer examination usually shows that it has been 

 built upon a tuft of grass or upon the stem of a bush, the branches of which 

 have been broken off close to the ground. Figure 22, plate 8, shows the 

 characteristic groupings of the nests. It is typical of many localities on the 

 island. Attention is called to the fact that the height of the nests above 

 the surface is quite variable. The noddies apparently do not seek to nest in 

 the thickest parts of the bushes. Although isolated nests are present even 

 where the shrubs are most dense, by far the majority of them are to be found 

 in bushes which border upon open spaces. When we consider the size and 

 delicacy of their wings this fact has biological value in that nests in such 

 situations are easy of access. Apparently there is no instinctive tendency to 

 secrete the nest. The cactus growth contains about 20 per cent of the total 

 number of nests. The nests there do not differ in construction from those 

 found in the bay-cedar bushes. 



By means of a mechanical counting device it was found possible actually 

 to count the total number of (active) noddy nests. The count gave 603 

 nests. In some places, where the bay-cedar bushes are very dense and the 

 area has to be covered " dog fashion '.' (or at times even still more primi- 

 tively), and in others where the cactus growth is very lu.xuriant, error in 

 counting was easily possible. On account of these possibilities of error. I be- 

 lieve that 700 nests is a more representative number. Since 2 birds occupy 

 one nest, we have a total of 1,400 adult noddies on the island. 



THE NEST OF THE SOOT^'. 



The nest of a sooty, when a nest is made, consists of a shallow oval de- 

 pression in the sand. This depression varies greatly in depth, depending 



' A test designed to answer this question was made. Before leaving the island, 

 I caught three birds on three separate nests. I marked the nests and placed a plati- 

 num band around the legs of the birds. During the nesting season, just past (190.S). 

 Dr. Mayer wrote me that he had captured the birds occupying these marked nesis 

 and thai none of tlic birds so ca['tiirc-d n'as inarl;cd zuitii flic plalinum band. It is 

 recognized that the number of birds tested in this way is too small to afford a basis 

 for generalization. 



" The nearest approach I found to the laying of the egg upon the bare ground 

 was in the case of two nests built on a bare horizontal board lying among the cactus 

 growth. In each of these cases the egg was laid_ directly upon the board, but some 

 dozen or two small sticks retained the egg in position. 



