( 278 ) 

 POLYGAMY AMONG ROOKS. 



BY 



ERIC B. DUN LOP. 



During the spring of 1910 I devoted a considerable amount 

 of time to studying the habits of the Rook {Corvus f . frugilegus) , 

 and much of interest was revealed. One point that appeared 

 was that the Rook is not always monogamous. 



At one Rookery a nest was built in a sycamore apart from 

 the remainder, which were for the most part in yews ; a good 

 view could be obtained of this nest, with glasses, from above, 

 as the trees were situated on a hillside. The nest was a small 

 one and unfortunately could not be reached by climbing, as 

 the branches in which the nest was built were too slender to 

 support any weight. 



Having previously noticed three Rooks about this nest, 

 on the evening of April 15th, I examined it carefully, and 

 found that two birds were sitting side by side in the nest 

 hollow, evidently incubating. 



Subsequently this nest was watched carefully, and, on 

 May 1st, about five minutes after they had been disturbed 

 by my approach, two birds returned and went on to the 

 nest, sitting side by side. 



After some time, one of them moved aside and allowed 

 the other to come off past it ; the former then resumed 

 incubation whilst the one that had left the nest preened its 

 plumage on an adjacent branch. Later the other came off 

 and also commenced preening. Shortly after the cock bird 

 returned with food, both the birds that had been incubating 

 shook their wings and cawed when they saw him approaching. 

 The nest contained small young, and the cock feci both the 

 hens and the young. He went olf again as soon as he had dis- 

 posed of the food. The two hens then went on to the nest, 

 coming off once or twice to preen their plumage later They 

 were on the nest at the end of half-an-hour when the male 

 returned, bu both immediately left it and greeted him with 

 much cawing and wing-shaking. The cock again left and 

 returned after another absence of almost exactly half-an-hour. 



The hens were on the best of terms and showed no siga of 

 jealousy. On May 4th the nest was again kept under obseiva 

 tion. The male was absent forty-three minutes bet,vco;i two 

 visits. One of the hens went off for a tiy and when .she 

 returned the other came off the nest and preened her plumage, 

 the former immediately taking her place. 



