368 THE GANNET 



birds are bound. 1 The period of departure is nearly as protracted ; 

 it extends from September into December, from which it appears that 

 the breeding-places are left unoccupied only during a relatively small 

 portion of the year, a few weeks at most. 2 



Gannets have been seen arriving on the Bass Rock in pairs, and 

 this is stated to be the general rule, the exceptions being provided by 

 birds which have lost their mates or are selecting them for the first 

 time. 3 The fact is interesting, because it is unusual : in the case of 

 most species of birds the males arrive first. It points also to the 

 conclusion that the birds pair for life. 



The proceedings of the birds which arrive at the breeding- 

 quarters unmated have yet to be closely studied. There is so far 

 no evidence that their sex displays differ in any respect from those of 

 the birds which arrive paired. The displays of paired birds may be 

 observed repeatedly any day throughout the breeding season, and are 

 of considerable interest, because they are performed by both sexes. 

 As they have not hitherto been recorded, I propose to give a full 

 description, basing the same upon a very large number of notes 

 written down at the time of observation, during a stay of several 

 days, in June and August, upon the Bass Rock (1909). The notes 

 were supplemented by a number of photographs. 



In its most complete form the gannet display is much as follows : the 

 two birds stand usually face to face, with wings spread and waving, and 

 with the tail bent down ; thus standing, they wag their heads violently 

 from side to side ; if they are close enough, their beaks collide with a 

 noise of castanets ; if still closer, the beaks no longer clack, but are, 

 so to speak, whetted one by the other, with something of the move- 

 ments of a knife playing on the steel. The performance is accom- 

 panied by a vociferous strident " urrah ! urrah f " which rings along 



1 See "Classified Notes," under Migration. 



1 From Sule Skerry the period of departure has been given as September to December ( J. 

 Tomison in the Annals Scot. Nat. Hist., 1904, p. 97). For the Bass Rock as late as December 

 (J. M. Campbell, in litt.). 



* J. M. Campbell, in litt. 



