THE TUBE-NOSES 



183 



Fig. 32 

 Breeding distribution of the storm- 

 petrel, Hydrobates pelagicus 



shearwaters of any other lasting 

 mutual bond, but, as mentioned 

 in the previous chapter, because 

 the pair meet and mate at the 

 familiar focal point of the nest, so 

 long as both shall live they remain 

 faithful for life. This was found to 

 be the case with a few exceptions 

 over many years with the Manx 

 shearwater and the storm-petrel, 

 and over two years with the 

 Wilson's petrel. 



Nest-occupation by all species of 

 petrels begins well ahead of the 

 laying of the single tgg. Thus ful- 

 mars arrive in November and Dec- 

 ember but do not lay until 5 May, normally not until after 12 May; 

 Manx shearwaters first arrive in February but do not begin laying 

 until the end of April; great shearwaters arrive in August and lay in 

 November; storm-petrels come to land at the end of April and lay in 

 June; Wilson's petrels are at least three weeks in preparing the nesting 

 burrow while the winter snows have scarcely left the land; and the 

 little shearwater in Western Australia apparently returns in January 

 but does not lay until the end of June. The exceptionally early return 

 of the fulmar and the little shearwater in the largest colonies may be 

 fundamentally associated with the pressure of great numbers of ex- 

 perienced adults in severe competition for the best nest sites; it is paral- 

 leled in the case of other sociable birds, e.g. the common guillemot 

 which returns (large colonies only) five months before laying begins. 

 Where colonies are of a smaller size the return is correspondingly 

 later in all these species, and many other sociable birds, including 

 the fulmar (Fisher, 1952). Nest-site pressure, however (it should be 

 added) is only one of many population-controlling factors. 



With the early return of the established breeders courtship activities 

 begin. They are not at first either prolonged or passionate but rather 

 preliminary. The Manx and little shearwaters and the fulmars on 

 arrival rest much and appear to sleep a good deal in the first few days. 

 Nor do they visit their territories regularly. The first arrivals may be 

 males — among albatrosses this is certainly the case. The night-active 

 petrels and shearwaters may miss one or two nights, and the day- 



