VOL. IX.] ON INCUBATION. Ill 



a nest was threatened by Crows, the non-sitting bird 

 always hastened to the assistance of the incubating bird. 



At the second nest, after one of the Gulls had settled 

 near it, it stood there for a time. On a Crow flying 

 past, the Gull ran towards its nest and almost at once 

 settled down on it. It left it again, but a G*row flying 

 over caused it to run on again. The Gull called in an 

 agitated manner whilst the Crow \\as about. After one 

 and a half hours the other Gull took up incubation. This 

 bird remained on for the last hour and a half that I was 

 in the blind. Tne non-sitting bird in each instance stood 

 near at hand . 



^Alien T entered the blind at 2 p.m. the nest held two 

 eggs : when I left at 5 p.m. it contauied three. At about 

 4.30 I noticed the sitting bird was very restless, and I 

 have no doubt that it was the second bird that went on 

 that laid the egg. 



With regard to the part taken by the male in incubation 

 in the case of ovitegous liirds, undue emphasis should not 

 be laid on the point, for m the case of various ovinudous 

 Limicoline birds the male shares the duties with the 

 female. 



That the Crows frequently did succeed in purloming 

 Gulls' eggs was a matter of common observation, the 

 shells of sucked Gulls' eggs being found on various 

 occasions under trees frequented by Cro\\'s. Selection 

 was evidently close, any carelessness on the part of Gulls 

 being promptly penalised by the loss of eggs. 



To determine just how close this selection was, I 

 moved several nests of the Herring-Gull from their 

 original sites and placed them in natural situations 

 some little distance away ; as birds return to the site 

 of their nest and not to the nest as such, the eggs were 

 deprived of the protection of the adults. I found that 

 as soon as a Crow came near the unprotected nest, it 

 was detected and the eggs immediately sucked. 



It is not unusual for the Herring- Gull to construct 

 an extra nest near the one containing the eggs. Such 



