NIDIFICATION AND INCUBATION 347 



many more than three can be laid.* Whether a Gannet 

 ever rears a second yomig one in a season is doubtful ; 

 indeed it is hardly likely, considering the forty-two days of 

 incubation, as well as the length of time during which a 

 young Gannet is helpless, and the nest consequently 

 required. 



Among birds which breed gregariously it must infallibly 

 happen, although they may normally lay but one egg, 

 that two will sometimes be seen in the same nest, but not 

 necessarily laid by the same bird, and this is not an infrequent 

 incident with the Gannet. But that there should be two 

 eggs, and both of them far advanced in incubation, as were 

 found by Dr. J. Wiglesworth on one occasion at Stack Lii, 

 must be very unusual, f That sea-birds not infrequently 

 sit upon one another's eggs has also often been suspected ; 

 to my mind it would be extraordinary if it were not so, 

 and it seems that mistakes of this kind are made by the 

 Gannet. { Visitors to the Bass Rock must have noticed how 



* See "Ber. Nat. CI.," 1873, p. 17. 



t " St. Kilda and its Birds," p. 49. Mr. O. G. Pike has also seen two 

 eggs, both incubated. 



X It is fair to mention that Mr. Laidlavv in May, 1907, daubed three 

 Gannets with paint of different colours, and for fourteen days he assures 

 me that each of these birds was always on or near the same egg, after 

 which, unfortunately, Mr. Laidlaw had to be away from the Bass, and his 

 assistant discontinued observations. 



