131 



number of stragglers from North America or Asia within a given 

 number of years we cannot say to a year when any particular 

 example will arrive. In a giveu period it might be safely pre- 

 dicted that there will be a certain number of accidents in the 

 streets of London or any large town, some of which may be said 

 to be governed by causes of a recurring kind, such as the pre- 

 valence of fogs and gales. Nevertheless, we still look upon these 

 casualties as accidents, not as the result of definite laws. It 

 should not be forgotten that the list of waifs and strays on 

 Heligoland is the result of more than fifty years of observation in 

 a locality " where literally not a bird escapes notice." Under 

 the circumstances, though the list is certainly a remarkable one, 

 Herr Gatke seems to attach far too great an importance to the 

 evidence it presents. 



He attributes the presence of these south-eastern species on 

 Heligoland to a most curious cause, i.e., the death of one of 

 a pair during the period of incubation. After an accident of 

 this kind the surviving parties, to satisfy the persistent impulse 

 towards accomplishing the act of propagation, commences the 

 migratory journey anew ! ! ! Such a theory is quite opposed to 

 all experience. Probably in no locality are the sexes of birds so 

 evenly balanced that each individual finds a mate. In some 

 species the males undoubtedly predominate. Under these cir- 

 cumstances it would be remarkable, if it were necessary, for the 

 female to undertake a fresh journey in quest of a new partner. 

 On the contrary, it is well known that on the death of either male 

 or female the survivor finds a new mate without any difficulty, 

 and over and over again it has been remarked with what wonder- 

 ful celerity this takes place. To take the case of the Black- 

 headed Bunting. Herr Gatke mentions that with the exception of 

 the young bird of the yeaf which was shot in August, all the 

 examples procured occurred between May 6th and June 18th, 

 i.e., from the commencement and during the height of the breed- 

 ing season ; and, moreover, of these, five were old males, three old 

 females, and lastly, a male in its second year. A further old pair 

 were added to his collection by Mr. J. H. Gurney; these facts 

 thus show that females occur nearly as frequently as males. 



It may be pointed out here that several common species, such 



