The Possibilities of Bird-Marking. 213 



&• 



But that this line of reasoning may prove dangerous if pushed too 

 far, is evident. Personally, I regard with some scepticism the following 

 interpretation of the southward wanderings of the Black-headed Gulls 

 (Zarus ridibundus) of a colony at Kossitten, where they are marked as 

 nestlings. Three routes are followed, we are told : one follows the coasts to 

 the Bay of Biscay ; the second goes so far, and then crosses by the Rhine and 

 the Rhone, and extends to the Balearic Isles ; the third crosses direct to the 

 Adriatic by the Vistula and the Danube systems, and extends to Tunis. All 

 this is based on about forty records ! (Thienemann, Journal fur Ornithologie, 

 1909, pp. 449-458, and plate viii.). 



The danger of this assumption of the existence of regular routes may 

 be still further realised by the consideration of certain cases in which such 

 regularity has been well shown to be entirely absent. Thus of the 

 Northumberland Woodcock {Scolopax rusticola) already mentioned, many 

 were found there at all times of their first and subsequent winters. Others 

 travelled south even to Brittany, others went west into Ireland, and still 

 others went north, far into Scotland — Argyll and Forfarshire (Lord William 

 Percy, Country Life, 27th Feb. 1909). Similar results were obtained in 

 Tyrone : some proved resident, some went east, some went south-east to the 

 south of England, and one went north-east to Inverness {Field, 17th Oct. 1908, 

 p. 717, and 24th Oct. 1908, p. 745). More recently a west of Ireland (Gal way) 

 Woodcock has been reported from Portugal {British Birds, iv. p. 280). 



Similarly in the case of the Black-crowned Night Heron (Nycticorax 

 naevius) of North America, it has been found that it is dispersal rather than 

 true migration which takes place (Bartsch, Smiths. Miscel. Coll., xlv., Pub. No. 

 1419, Quart. Issue, vol i., pts. 1 and 2, pp. 104-111, pis. xxxii.-xxxviii. : and 

 Cole, Auk, xxvii., No. 2, pp. 160-164). 



These are just a few of the more striking results obtained at the present early 

 stage of this new study. I hope that they will at least serve to show what may 

 be expected of the method when it has been longer and more widely in use. 



IV. The Aberdeen University Bird-Migration Inquiry. 



As already stated, this Inquiry was established in 1909 on the lines of 

 the Rossitten Inquiry : I may add that I had visited the Rossitten Vogelwarte, 

 or ornithological station, during the previous autumn, and that I have since 

 re-visited it (autumn 1910). It will thus be understood that I am chiefly 

 indebted to Dr Thienemann for guidance in the matter of methods, but I 

 have also derived some benefit from " exchanging notes," so to speak, with 

 Mr Mortensen, Mr Witherby, and Messrs Herman and Schenk of the 

 Hungarian Central-bureau. 



