Powers of Vision 297 



practical darkness within, or into what might at best be 

 described as but a very " dim religious light." Yet they 

 seemed to experience no inconvenience from the sudden 

 change, but at once found their way to their nests, which 

 sufficiently demonstrates the marvellous adaptability, and 

 power of their vision. 1 Some of the nests were on the 

 "wall heads," others in crevices and at the base of rafters, 

 but many were on the floor ; and from the latter, of course, 

 the birds had to rise in the circumscribed area of the loft, 

 in order to gain the window. None of them showed any 

 difficulty in accomplishing this during our visits ; but 

 should they fail, as my friend from previous observations 

 had some reason to think might sometimes happen, their 

 resources are not at an end. With feet and bill, a Swift 

 can creep up the face of any reasonably rough wall, and as 

 a last resort, the window can, without difficulty, be gained 

 in that way. A noteworthy difference between the behaviour 

 of the birds outside and in was that, while they frequently 

 continued to scream as they hustled their way over the 

 window-boards, from the moment they dropped inside, not 

 a note was uttered. Two is the ordinary number of eggs 

 laid, but some nests may always be found containing three. 



In this country it is very rarely that the Swift takes to a 

 tree for a nesting site ; but in the forest of Rothiemurchus, 

 in Strath Spey, I have seen them issuing, four or five 

 together, from old Woodpecker holes in the bare and 

 almost branchless trunks of some of the ancient pines that 

 still stand here and there over the hillsides. The hoary 

 head of one of these giants was crowned for many years by 

 the remains of an Osprey's nest, while a pair of Swifts occu- 

 pied a hole beneath it ; but that was more than twenty years 

 ago, and in the interval the Ospreys have disappeared. 

 From its dimensions, both birds were to be excused if they 

 mistook the trunk for some ruined tower, their more 

 ordinary resort. 



Young Swifts are at first blind and naked, and their 

 development is slow in comparison with other small birds ; 

 before the feathers appear, they become covered with a 

 1 See also the reference to cave-building swifts on page 314. 



