78 BRITISH BIRDS. [vol. xiv. 



when the eggs are being laid, and for a number of days after- 

 wards, the hen bird sits almost continuously. At irregular 

 intervals, which may be as short as half an hour, but which 

 are usually a good deal longer, the hen will leave the nest at 

 the approach of the male. She stands in the neighbourhood 

 of the nest or flies away while he goes on, but her absence is 

 of brief duration ; five or ten minutes do not pass before she 

 comes again. Usually the male then leaves the nest at once 

 and flies or stands around, sometimes she urges him off the 

 nest by prodding beneath him with her bill. These short 

 rests afforded to the hen bird by the male were recorded at 

 three nests by repeated and daily observations, and I believe 

 them to be the rule. In my experience the eggs are never 

 left uncovered willingly for longer periods than a few minutes, 

 however hot or sultry the day. Incubation is continuous. 

 The Terns show an evident anxiety to keep the eggs covered 

 and return to the nests with much boldness. It is during 

 these same days of laying and early incubation, while the 

 hen bird is almost always on the nest, that she is fed by her 

 mate. At some nests, especially those viewed at a distance, 

 a fish was seen to be brought at almost regular intervals of 

 five to ten minutes over periods of an hour or more. At the 

 nests before the tent the intervals were generally longer, a 

 half hour or even more. It is the rule for the hen to be fed 

 without leaving the nest if the birds show no signs of nervous- 

 ness, though there are exceptions. In nests placed before 

 the tent, the hen is fed on the nest or at some little distance. 

 If fed while sitting, she rises off the eggs to swallow the fish, 

 standing in the nest's cup and just exposing the eggs. She 

 always greets her mate as he flies over or around with loud 

 cries, which are continued up to the moment when the fish 

 is taken. She may move a foot or more off the nest and take 

 the fish while standing, returning almost at once to sit. When 

 the male is nervous he may call her off the nest and feed her 

 twenty paces or more from the nest or even at the edge of the 

 sea. In some of these last feeding scenes, just before the fish 

 was taken and at the meeting of the two birds, their heads 

 were wagged slowly and regularly from side to side. 



During the early days of incubation, when the male bird 

 is about to take the place of the female for a few minutes, a 

 curious incident is often seen. As he flies over or approaches 

 by running over the sand, she picks up, as she sits, fragments 

 of pebble from the surrounding sand, bringing them into the 

 cup of the nest and depositing them. It is a signal of the 

 coming change of place M-hich rarely fails. When he actually 



