342 ANNUAL REPORT SMITHSONIAN INSTITUTION, 19 39 



point, which is a mile from my own house on the east side of the island. 

 There is good soil above the old red sandstone rock of which the visible 

 cliffs are composed. 



I had a great deal to do when I first landed on the island 10 years 

 ago, for the cottage was in ruins, but I am not going into that aspect 

 of my island life tonight. SuflBce it to say that I was attracted to the 

 island in the first place by its great wealth of sea bird life. Later, as 

 opportunity afforded, I began to look into the individual lives of these 

 birds. 



The first essential in such a study, since individual sea birds of one 

 species are more exactly alike than peas in a pod, was some method of 

 marking. Color marking of plumage, which we at first tried, was un- 

 reliable — the birds soon preened off the most tenacious pigment when 

 they got back to the sea. Clipping portions of certain feathers was 

 open to objection as mutilating the plumage, and anyway these marks 

 were lost in the annual molt. Then I heard of Mr. Witherby's scheme 

 for marking birds with numbered leg rings. This scheme, which is 

 now taken over by the British Trust for Ornithology and is housed in 

 the British Museum of Natural History, is not as well known as it 

 deserves to be, for it has certainly revolutionized bird study. 



There are seven sizes of rings to suit all species of British birds 

 from a wren to an eagle. Each ring has a serial number and the 

 inscription "Inform British Museum Natural History, London," so 

 that those who capture alive or find dead a bird with such a ring will 

 know what to do in the interests of scientific bird study. I may add 

 there are similar ringing schemes in operation today in many other 

 countries. 



All birds are not easily caught and so do not lend themselves to 

 ringing, but some sea birds do. I started with the Manx shearwater, 

 Pv^nus puffiiius puffimis (Brunn) , a bird whose habits were at that 

 time very little known (1, 2).^ It is rather a helpless bird on land 

 and is easily killed by predatory gulls and hawks. For that reason 

 it spends the day at sea or in the depth of a rabbit burrow on the 

 island, only returning from sea or coming out of its nesting hole 

 when the night is sufficiently dark to make it difficult for the predators 

 to see it. I say sufficiently because I soon found that if the moon 

 were visible on any night the shearwater refused to appear, even 

 though earlier in the evening, just before sunset, it had assembled 

 ready to land, gathering in great flocks on the sea near the island. 

 But on a dark night the shearwaters arrive in thousands, making a 

 great uproar with their unearthly screams, and for the few hours of 

 summer night carrying on the business of nesting. There are proba- 

 bly 10,000 pairs breeding on Skokholm. 



* Numbers in parentheses refer to list at end of article. 



