204 Papers from the Marine Biological Laboratory at Tortugas. 



eral weeks of nest-building. It has been mentioned that the noddy never 

 full)^ completes its nest; but after the egg is laid the gathering of additional 

 nest-material is a sporadic activity. 



The first eggs were noticed on May 4. On May 6 I marked 16 nests 

 and visited each twice daily. The first egg was found in these nests on the 

 nth ; not until the 25th did each nest contain its egg. My chart shows that 

 the majority of the eggs were laid from the nth to the i6th. Fisher^ has 

 the following to say concerning the appearance of the egg: 



The rather acute ovate egg is a creamy white, sparsely spotted with Hght gray, 

 burnt umber, and walnut brown. Most of the brown spots are on the larger half, 

 and are sometimes small and at other times quite large (4 to 8 mm. across). One 

 egg has no dark marks, but is scantily spotted and streaked with light Mars-brown. 

 Specimens vary from 58 by 48 to 51 by 35 mm. 



After the egg is laid, a marked change appears in the behavior of both 

 the male and the female. The birds will now attack even a human intruder, 

 and their defense of the nest against their own kind becomes even more 

 strict than before." Oftentimes the birds will sit on the egg and allow 

 themselves to be caught, striking viciously all the while with their long, keen, 

 pointed beaks. Individuals vary greatly in this respect. On my daily 

 rounds, as I approached the vicinity of a group of nests, several noddies 

 would usually advance to meet me, striking viciously at my head. Their 

 attacks would continue until I withdrew. Many times I have had my hat 

 knocked off and the blood brought from my scalp by their vicious attacks. 

 This change in the behavior of the noddies, which is so marked and which 

 begins so abruptly, will be spoken of again further on in the paper. It may 

 be said here that the stimulus to the change is to be sought for in the tactual 

 and visual impulses aroused by the egg. 



Still another marked change occurs in the habits of the birds: The male 

 no longer feeds the female. Each bird takes equal turns at brooding the egg. 

 My attention was first called to this while I was watching the habits of the 

 birds before the egg was laid. Several nests in the vicinity of the place of 

 observation already contained eggs. At these nests I was never able to 

 observe the feeding of the female by the male. At this period the two birds 

 become practically automata. Their life is taken up in alternately brooding 

 the egg and in feeding. The birds spend little or no time together except at 

 night. The one coines to the nest, the other flies away to feed. 



When the returning bird (which I designate R) arrives at the nest, 

 the bird on the nest (which I shall designate O) may or may not imme- 

 diately react to it. To take the most rapid case of immediate " relief " at 

 the nest first, we find R returning and alighting on the rim of the nest. R 

 nods to 0. nods in return. This continues for a moment, when takes 

 flight. R immediately covers the egg. 



; Op. cit., p. 783- 



" See Thompson, op. cit., p. 81. 



