35 



our eastern coasts are derived from the former country, as at 

 these particular periods there has been either no corresponding 

 rush over Heligoland, or the species has occurred there in sm&,ller 

 numbers than usual. Indeed it vfill be gathered from a remark 

 of Herr Gatke's on p. 15, that mass migrations of this species 

 rarely pass the island. 



To enable these large flights to collect together, a certain 

 amount of concentration on to particular stretches of the 

 Scandinavian coast-line must of necessity take place. It cannot 

 be imagined that all the individuals in a particular district, which 

 might have an area of many square miles, set out from their 

 nesting stations at an identical moment. Probably the first 

 move is down some broad and well-timbered river valley to the 

 sea. On arriving at the latter, the various flights are banded 

 together whilst waiting the advent of the anti-cyclonic conditions 

 80 necessary during the migrations of so feeble a species. 



On these conditions becoming prevalent the majority will 

 probably take early advantage of the opportunity to at once 

 undertake their flight over the North Sea. In crossing the latter, 

 however, there can hardly fail to be a considerable amount of 

 spreading amongst the flocks. Prom this fact, and also from the 

 probability that there are many starting points, the flights on 

 reaching our islands will affect a considerable length of coast line. 

 Moreover, all do not proceed directly inland ; many will continue 

 the journey by following the latter to the south, and as these 

 rushes occasionally extend over a period of several days, flocks 

 which have really arrived in the north, and have since travelled 

 many miles further, may come to be regarded, in other locaUties 

 through which they may pass, as new arrivals from over the sea. 

 Thus so far from having conducted the migration in a broad front 

 corresponding to the latitudinal area of the breeding grounds, 

 the flight has been reaUy performed in several narrow columns, 

 which have become partially dispersed in crossing a wide sea. 



Herr Gatke in later chapters of his work alludes to large 

 flights of Plovers, Curlews, Godwits, Sandpipers, Oyster-catchers 

 and other species occurring late in the year, at times quite beyond 

 the ordinary migration period of these species. These supplemen- 

 tary migrations are usually accompanied by the advent of severe 



