VOL. XIV.] xNOTES ON THE LITTLE TEKN. 79 



comes to the nest, she rises and walks off ; but not infrequently 

 she continues to pick up stones, sometimes quite large stones 

 or bits of stick, and jerks them to one side with a sharp move- 

 ment of her head. A similar action is witnessed in the case of 

 the Ringed Plover. This curious display on her part takes 

 place while the male is arranging the eggs beneath him 

 preparatory to sitting, and of it he seems always sublimely 

 indifferent. The purpose, if it has a purpose, is not at all 

 clear. I can record it of the female only, though unable to 

 assert that the action is performed by her alone. Presum- 

 ably it constitutes the remnant of a nest -repairing instinct, 

 which is all but dead in these birds. The sole repair necessary 

 in a Tern's nest is an occasional deepening of the sandy cup ; 

 this is frequently necessary when the sand is drifting. It is 

 accomplished by rotating her breast upon the nest and flinging 

 out the excess of sand backwards with the feet ; a fact which 

 has been recorded in the case of other species, but not, I 

 think, of the Little Tern. In scooping out the sand, the 

 bird rests forward on her sternum and the depressed angles 

 of the wings. 



During the later days of incubation (conclusive observations 

 on one nest only) male and female Tern incubate for alternate 

 periods of approximately an hour. At this nest the new 

 regime started about the fourth day after the laying of the 

 last egg and was continued regularly for two weeks. With 

 the changed regime the male no longer brought fish to the 

 female, each bird hunting its own prey. 



It may be asked how the male and female birds were 

 identified. Such identification was absolute at two nests, 

 to which most of my notes refer, for in one an egg was laid 

 while I was in the tent, and at the other the pairing of the 

 birds was seen quite close to the nest ; it occurred actually 

 during the period of incubation. At the third nest identifica- 

 tion was by inference ; the bird constantly on the nest during 

 the early days of incubation was naturally regarded as the 

 female. At all these nests the bird identified as the male 

 brought fish to its sitting mate. At each nest, a very few 

 hours in the company of the birds made disiiinguishing marks 

 clear, and the male or female could be recognized almost at 

 the instant it came in view. At all nests I made careful 

 sketches of the birds' heads, seen in side view, copying 

 accurately the smallest irregularit}^ at the margin of the black 

 cap. Of the six birds none were alike in this respect ; the 

 little variations at the meeting of black and white were in 

 themselves sufficient to identify any one of the six. Judging 



