22 2 Papers from the Marine Biological Laboratory at Tortitgas. 



Sooty No. 2. — This bird was carried to a position within 20 feet of its 

 nest and released there. The mate was not present. The marked bird, 

 instead of going directly to the nest and covering the egg, alighted some 10 

 or 15 feet from it and attempted to walk past other nests in the vicinity. 

 A commotion was immediately raised. The other birds brooding their eggs 

 left them to attack this strange object. This bird ran rapidly out of my 

 sight, being fought at every step, and disappeared for 10 minutes. At the 

 end of that time I saw it approaching its nest. Three feet away from its 

 nest it was halted by a row of hostile beaks. It left again and at the end 

 of half an hour put in an appearance. Again it could not reach its nest. 

 (A rather amusing incident occurred at this point. A noddy in search of 

 a stick alighted near this marked sooty. The noddy is usually utterly ob- 

 livious to the presence of the sooty when in search of his precious sticks. 

 Such was not the case in the present instance. He dropped his stick, peered 

 at the sooty, extending his head toward it and craning his neck in a most 

 peculiar and unwonted fashion.) After some 2 hours had passed this bird 

 finally reached its nest and covered the e^^^%. The mate on returning^ 

 showed evident signs of restlessness and disturbance, but finally took up a 

 standing position near the nest. At my approach some 2 hours later the 

 unmarked bird crawled from the nest and the marked bird crawled on. 

 Evidently the family difiference had been satisfactorily arranged. 



These tests upon the marked sooties, in so far as they show anything of 

 a satisfactory nature, lead us to believe that a change in the visual appear- 

 ance of the bird is immediately noticed both by its mate and by the other 

 sooties on the island. The disturbance caused by the appearance of these 

 strangely marked birds was very much more pronounced than was the case 

 with the noddies. Such experiments naturally leave the problem of recogni- 

 tion of mate by mate almost untouched. It is a problem, however, which I 

 believe can be attacked experimentally. 



TESTS ON RECOGNITION OF THE EGG. 



Since the nest is also accurately localized by both the noddy and the 

 sooty, I desired to test whether the egg, the nest, and the nest locality were 

 all of importance in this reaction. I made tentative efforts to arrive at some 

 conclusion as regards this question. 



As a preliminary step I colored the eggs of both the noddy and the 

 sooty and then watched their reactions under the changed conditions. The 

 noddy eggs were colored with vermilion, blue-green, and violet aniline dyes. 

 The birds immediately covered these eggs without the slightest change in 

 their behavior being apparent. Eggs similarly colored with Higgins' black 

 ink produced no disturbance. Hen eggs and sooty eggs and eggs made of 

 magnesium sulphate were likewise accepted without question. 



In this connection, an interesting incidental observation was made. .\ 

 noddy before it lays its egg has habits diiiferent from those which char- 



' Since the bird was released in the morning, I was forced to sit near this nest 

 until the mate returned — about 8 hours later! 



