ON THE MIGIUTION OP BIRDS. 193 



ousels, song-thrushes, and swallows were seen around the lirrbt. Of 

 these there struck the glass : one land- rail, one water-rail, four ring- 

 ousels, and 100 swallows. At the Casquets, wliich is a revolving light 

 the larger birds follow the rays, but do not often strike the glass. 

 Some of the reporters state extreme height above the sea, as a cause of 

 birds seldom or never striking the glass, or being seen hovering around 

 the light. Certainly returns show a preponderance of deaths first at 

 light- vessels, whose average height above the sea is only a few feet • 

 secondly, at such stations as the Bell-rock, Dhuheartach or Skerry- 

 vore, whose lanterns are not higher than sixty or seventy feet above 

 the sea. 



With such favourable passages as light head-winds afford, the 

 migrants are so little fatigued that they do not alight on reaching land, 

 but keep on their course to the interior. At other times with adverse 

 winds they drop on reaching the shore, being hardly able to struggle to 

 land. 



The observations show beyond doubt that all birds are migratory (if 

 we except our common game-birds, and perhaps the green woodpecker). 

 Even such comparatively weak-winged birds as the gold-crested ivren, 

 common wren, the titmice, hedge-sparrow, common sparrow, and redbreast 

 change their locality, crossing the North Sea in large numbers. At 

 Heligoland, Herr Giitke remarks (in the very comprehensive and highly 

 interesting notes sent to us), ' Up towards the end of July, all yoano- 

 sparrows disappeared from the island,' and ' up to the middle of Sep- 

 tember nearly all old sparrows had quitted' the island.' On October 10 

 there was ' an influx of fresh sparrows,' probably arriving from some 

 more northern region. 



As a rule, the young of the year migrate some weeks in advance of 

 the old birds ; this holds good with all orders and almost all species. In 

 the spring the males often migrate in advance of the females. In sprint, 

 birds migrate, with rare exceptions, at night, and as the weather is then 

 finer, and the nights shorter and clearer, do not fly low and run their heads 

 so much against the lanterns of lighthouses and lightships. The sprint 

 migration is also carried on much more leisurely, migrants;' proceeding 

 by easy slopes northward, and there are none of those great ' waves ' 

 or ' rushes ' which are so characteristic of the autumn migration. The 

 notes on spring migi-ation taken in 1879 and 1880 point also to the con- 

 clusion that, at this season, migrants strike the glasses of lanterns fi'om 

 11 P.M. to the dawn of day, the majority after midnight, and not also in 

 the early hours of night, as is the case in the autumn. 



It is remarkable how suddenly the stream of migration commences 

 running, and how suddenly it stops again ; it may be from 8 a.m. to 1 p.m. 

 there is a continual stream of various migrants arriving on our coasty, 

 and then, or at least for that day, migration is apparently over, and not 

 another bird is seen. 



The time of migi-ation of any particular species extends over a con- 

 siderable period. Sometimes it is over four or five weeks, in other cases 

 going on for months or even half-a-year. Indeed, birds seem to be 

 crossing the North Sea all the year round, and no sooner does the ebb of 

 the autumn migration cease — and it is prolonged into February — than 

 the flood sets in, and birds are passing northward again. In every case 

 of normal migration, any given species will continue to pass day by day, 

 or week after week, till it attains the maxinaum in ^ ' great rush,' the 

 1881. ' 



