56 REPORT ON THE MIGRATION OF BIRDS. 



at some point north of Tweed, would, I believe, soon show us 

 whether the preiDonderance of records south of the Tweed is 

 entirely due to old-established lines of migration., or to the 

 number of light-vessels on the English coast, or partly to both. 

 It would, I think, assist in proving or disproving theories of land- 

 communications which have been advanced and disputed by 

 previous writers. At present we cannot positively state from 

 our present data whether an actual or only an apparent pre- 

 ponderance of birds pass south of the Tweed in autumn. It 

 appears a little curious to find, however, a highway of migration 

 by the Pentland Firth so much further north than the stations 

 mentioned. Writing from North Eonaldshay Mr. TuUoch 

 remarks upon the usual scarcity of birds there, and says 

 '' they keep more direct for the mainland " ; and he re- 

 marks also upon the abundance of birds seen in September 

 and November at Pentland Skerries, where he was lighthouse- 

 keeper for fom- years. He remarks on the abundance of Mountain 

 Thrushes, Blackbirds, Owls, Woodcocks, Wrens, Robins, and 

 Titmice which occur there when the wind is from the east, and 

 from which station I have a large numerical return this year. 

 This at first sight appears to be a contradiction of what I have 

 said about the bulk of the birds passing south of Bell Rock, but, be 

 it noted, the prevailing winds at Pentland Skerries from August 

 23rd to September 12th were from points between north and 

 south by east, but never by west, and- thereafter, between 

 September 14th and October 10th, they were prevailing south to 

 south-west, but never west or north-west. From October 14th 

 they backed to north-east, and easterly winds again prevailed 

 here on till late in November. The isolated position of the 

 lights at Pentland Skerries, combined with the local prevalence 

 of easterly winds, is perhaps sufficient to account for the large 

 mass of the records. At all events I think the Pentland Skerries 

 returns are deserving, both now and in future, of special atten- 

 tion and study, and I look ujpon it as a particularly interesting 

 station. 



Isle of May stands this year at the head of the list for nume- 

 rical returns, I having received seven full schedules from Mr. 

 Agiiew, principally referring to autumn migration. Next comes 

 Bell Rock, but two out of three schedules refer to spring 

 migration, of which more anon. Then Sumburgh Head and 



