284 CORVIDJE. 



converse position be true or not. Now that hybrids of the 

 Black and Grey Crows are fertile has been proved by several 

 observers, and Mr. Seebohm has furnished (loc. cit.) addi- 

 tional evidence of the fact. But he has at the same time 

 come to the conclusion that though this is the case in some 

 instances it is not always so, and he bases his opinion on the 

 circumstance that at one place in that part of Siberia which 

 is tenanted in common by both forms he, in the breeding- 

 season, shot all the Crows he could thirteen of them being 

 "thoroughbred" and fifteen hybrids. Of the latter seven 

 were males and eight females, but the proportion of the sexes 

 in the former was very different, being eleven males and two 

 females. Hence he naturally supposes that most of the 

 " thoroughbred " females were engaged in incubation and 

 out of his reach, while the majority of hybrids were not, and 

 for the reason that they were barren. Whether this reason 

 be valid must be left to future determination, but if the 

 tendency to infertility, which Mr. Seebohm believes himself 

 to have observed, be finally established it must be allowed to 

 have due weight upon this very curious question*. 



Like the Kaven, our Crows seem to pair for life, and, 

 though some few pass the winter in or near their breeding- 

 haunts, whither their presence may attract chance strangers 

 of their kind, the greater number, including all the young 

 birds, collect in flocks towards the end of summer in places 

 where food is most abundant, and keeping more or less 

 together gradually make their way southward until the turn 

 of the season, when they retrace their flight in like manner. 

 Gregarious as they thus are during the greater part of the 

 year, they appear to associate less from the love of company 

 than from the opportunities thereby afforded of performing 

 their migrations in safety, or of getting their living with 

 facility. In the breeding-season the flocks separate, and 



* Some doubt however may be expressed as to whether all the birds deemed by 

 Mr. Seebohm to be " thoroughbred," were really so, for it seems that hybrids 

 of the two forms, as often as not, wholly resemble either one parent or the other, 

 while an entirely Black bird has been seen in a brood of which both the parents 

 were Grey (Verhandl. zool.-bot. Ver. Wien, 1854, p. 619). 



