THE NIGHTJAR :i7l 



The extraordinary resemblance of the bird itself to the bits of 

 bark and wood union*; which it site has often been noticed. So close 

 is it at times, that though knowing the position of the nest, one may 

 be quite unable to tell whether or not the bird is there. A good 

 instance of this is given by Mr. Edmund Selous, one of the very few 

 naturalists who hat demoted close attention to the apodal. " It was 

 midday in June, and a sunny day as well. I had left the bird in 

 question for a little while, to watch another, and, when I returned, 

 it was sitting in the same place, which I knew like my study table. 

 My eye rested full upon it, as it sat, but not catching the outline of the 

 tip of the wings and tail across a certain dry stalk, as I was accus- 

 tomed to do, I thought I was looking at a piece of fir-bark one of 

 those amongst which it sat I, in fact, looked for the eggs upon the 

 bird, for I knew the exact spot where they should be ; but, as I should 

 have seen them at once, owing to their light colour, I felt sure they 

 must be covered, and after gazing steadily for some time, all at once 

 -by an optical delusion, as it seemed, rather than by the passing 

 away of one the piece of fir-bark became the nightjar." 1 



The protective value of the nightjar's coloration is further in 

 creased by the fact that when sitting by day, possibly also at night, the 

 bird keeps its eyes almost shut, leaving only a narrow transverse slit 

 between the lids, through which to keep watch. 3 That this habit does 

 not arise from any sensitiveness of the eyes to light is clear from the 

 fact observed by Dr. Heinroth, that his tame nightjars would fix their 

 eyes wide open upon the sun without showing any signs of discomfort 

 The bird's love of basking and taking dust-baths in the sunlight 

 points to the same conclusion. The above authority also noted that 

 the birds were able to make the pupils of both eyes converge at the 

 same time towards the back angles of the lids, a fact which he tested 

 frequently by holding food behind their heads. The expression that 

 resulted was almost demoniacal, as may easily be imagined. This 

 ability to keep watch on what occurs behind, without turning the 



1 Bird lAfe (ilimpsr, p. 40. * Dr. Heinroth. op. 



VOL. ii. SB 



