1 92 1.] Bird-Migration by the Marking Method. 481 



from other sources where special opportunities for obtaining 

 records do not enter into the question. 



In the sections whicli follow the comparisons made with 

 the results of other investigators are by no means exhaustive. 

 The species successfully studied abroad are for the most part 

 unimportant in this country, so far as records go, and the 

 results of the ' British Birds ' inquir3' {2&), which are the most 

 important for this purpose^ have as yet been published in 

 collected form only in the case of a very few species. 



The Numbers of Birds marked during the 

 Aberdeen University Inquiry. 



Table I. shows the total numbers of birds of different 

 species marked during the course of the investigation. In 

 the third column the number of reappearance records is 

 given, and in tlie fourth column the percentage of marked 

 birds which have reappeared. The figures may be regarded 

 as complete for all practical purposes, as additional records 

 have, at the time of writing, become very infrequent. From 

 the numbers and percentages of reappearance records the 

 following are excluded : — 



(a) Records of birds recovered at the same place on the 

 day of marking, or, in the case of young birds, 

 within the flightless period ; 



(A) Incomplete and faulty records which have not been 

 considered sufhciently well established to be in- 

 cluded among the results ; 



{<•.) Second and subsequent records for the same bird. 



The percentage is not calculated for species of which less 

 than fifty individuals were marked, and it should be accepted 

 with reserve in cases where the total is less than some 

 hundreds. 



Detailed summaries of the numbers marked are given in 

 the case of certain of the more important species discussed 

 at length in the subsequent [lages. 



