86 THE SCOTTISH NATURALIST 



in appearance amongst the individuals of a species exists 

 only to human observation. The readiness with which 

 birds recognise their mates from amongst others, even when 

 at considerable distances, argues an individuality readily 

 appreciable by the birds themselves. Leaving on one side 

 the question of the factors originally determining choice, 

 the fact that pairs remain in company for many weeks 

 prior to the nesting season is proof of a mutual preference 

 over other possible mates. If no such preference existed, 

 then change of partners should be of constant occurrence, 

 daily and hourly. Some mutual link exists between the 

 paired birds, and one must assume that it is comprised by, or 

 contained in, a group of visual perceptions, whether these 

 relate to colour, movement, form, or attribute beyond human 

 analysis. But if it be granted that the basis of union is 

 represented by a preference due to certain visual perceptions, 

 then it is theoretically credible, or even probable, that similar 

 stimuli may be determining or guiding agents in the original 

 choice. 



Speaking of Mallards in confinement, Mr J. Lewis Bonhote 

 says 1 : "There is no doubt that ducks choose their own 

 drakes, and in this species at least it seems more than likely, 

 that sexual selection plays a considerable part. In most 

 cases birds once paired will, if opportunity occurs, mate 

 again every year, although they may have been separated 

 during the winter." If these remarks are justified, then the 

 possibility of accidental mating is negatived, and selection is 

 a certainty. Captivity frequently profoundly modifies the 

 activities of a species, and it is unsafe to assume that what 

 takes place in confinement necessarily represents the course 

 of events in a state of freedom ; but the theoretical possibility 

 of choice receives confirmation. 



To sum up : sexual selection occurs in the Mallard. 

 Such selection is almost certainly not "accidental." The 

 influences governing or directing the choice of the female 

 appear to take the form of certain stimuli provided by the 

 display of the male, the external attributes of the male, or 

 the cumulative effect of both. 



1 J. Lewis Bonhote: Avicult. Mag. t 3rd series, i. (1909-10), p. 301. 



