LETTER II. 47 



decreases as the season advances, and latterly ceases altogether ; 

 this is probably accounted for by the birds falling off in condition 

 during the time of sitting. 1 



The direction of the galleries may be ascertained by thrusting 

 up a ramrod, for they take frequent and abrupt windings ; a large 

 block of the soil may then be cut out with a spade ; and the 

 soil, though soft, is so tenacious that these blocks may all be 

 returned to their places again ; and the burrow not being 

 destroyed, is sometimes tenanted again next season. The birds 

 come to their holes in the first week in June ; the eggs . are laid 

 by the first week in July; and on the 13th of October I have 

 found the young very recently hatched. I once kept a pair and 

 succeeded in rearing one ; the other one was killed by accident. 

 They would take small pieces of fish very readily, and were more 

 active at night than during the day. The young one when fully 

 fledged differed from the adult merely in being of a rustier black, 

 and having an ill-defined white mark across the wing, formed by 

 the pale tips of the secondaries. Both the young and the old 

 ones, when confined in a basket or bag, escape at the smallest 

 aperture, climbing up the sides like mice, in doing which they 



1 When reading this account of the Petrel galleries of Soay or elsewhere, it 

 should be borne in mind that some of these same tunnelled dwellings may be 

 occupied by very different animals. Thus Shieldrakes use them, and also the 

 Otter. But Otters' holes are easily distinguished, having no side tunnels, and 

 being much more extensive, reaching to a distance at times of 15 feet in length, 

 with an average diameter of 12 inches, the sides and roof being smoothly polished 

 by the rubbing of the animals' fur in passing out and in ; with circular or oval 

 chambers, in which they rest, occurring at intervals ; and the drainage system 

 admirably adapted to carry off superfluous water ; and the rejectamenta of their 

 feasts carefully disposed in a side chamber a foot or more from the entrance of 

 the tunnel. Such a habitation we ourselves have seen in Soay. ED. 



