24 BRITAIN'S BIRDS AND THEIR NESTS. 



high above sea - level, makes their discovery improbable 

 till the observer has some clue to their whereabouts. 

 And no such clue is afforded by the birds, for most of 

 them are nocturnal, or at least crepuscular, in their habits 

 during the breeding season. 



The Petrels include many different kinds of birds, 

 showing a great range in the matter of size, varying 

 from the small, true Petrels to the great Albatrosses, 

 some of which are among the largest of present-day 

 flying birds. One peculiar characteristic is shared by all 

 — namely, that the nostrils terminate externally in tubes 

 along the top of the beak. These tubes are at once 

 noticeable in a specimen ; and even at a distance they 

 give the outline of the beak an irregular appearance, by 

 which, without further trouble, a bird is identified as a 

 member of this order. 



Although southern oceans are the headquarters of the 

 Petrels, four different kinds nest regularly in the British 

 Isles. But as they frequent for this purpose some out- 

 lying islands, and for the rest keep out to sea, the stay- 

 at-home British naturalist is not likely to know them 

 well from personal observation. During storms, however, 

 examples of various species are not infrequently captured 

 inland in all parts of the country. 



Of the four, the most abundant is the Storm or 

 Stormy PetreL The Scilly Isles are its only English 

 haunt, but it is foinid to a slight extent on the 

 Welsh coast. It is most abundant, however, on the west 

 and north coasts of Ireland and Scotland, and especially 

 on the islands off these coasts, from the Blaskets to the 

 Shetlands. 



To these haunts the Storm Petrels come at the end of 

 April or, more often, early in May. The nesting-sites are 

 crevices in the cliffs, or imder stones, or are burrows 



