MIGRATION IN THE BRITISH ISLANDS. 259 



from year to year ; sometimes it is completed in a 

 few weeks, sometimes it extends over as many 

 months. It is also worthy of remark how suddenly 

 Migration will sometimes commence or cease. I 

 have seen migrants coming for several days across 

 the North Sea to the Wash — Larks especially — 

 and for say three or four hours every morning, or 

 all night, up to 10 or 11 a.m. the stream would 

 flow, and then cease for the day. Hooded Crows 

 often do this, migrating for days together in the 

 morning. The first scattered flocks may be noted 

 soon after sunrise ; many alight on the mud-flats to 

 feed or to rest, but the majority pass on to more 

 inland districts, or set a southerly course along the 

 coast-line. The irregularity of their appearance is 

 sometimes remarkable. First perhaps an odd bird 

 or so comes along ; then in a few minutes a party 

 of eight or ten ; whilst at longer intervals occasional 

 flocks appear, all flying in a slow, laboured, yet 

 powerful manner, the individuals scattered about 

 with no apparent approach to order. 



The Mortality among these mighty bird hosts 

 must be appalling, stupendous ! The thousands of 

 these pilgrims of the night that yearly kill them- 

 selves against the lighthouses and light-vessels 

 round the British coasts represent a mere trifle in 

 the general rate of mortality ; the greater number 

 perish at sea ! In any case the sadly significant 

 fact is only too apparent that only a fragment of 

 these bird swarms — countless, one was going to 

 say, as the sands on the shore — returns in spring. 



