4 o BIRD LIFE GLIMPSES 



mention the extraordinary resemblance which the 

 nightjar bears to a piece of fir-bark, when it happens 

 to be sitting amidst pieces of fir-bark, and not amidst 

 other things, which, when it is, it no doubt re- 

 sembles as strongly. If, at a short distance, and for 

 a considerable time, one steadily mistakes one thing 

 for another thing, with the appearance of which 

 one is well acquainted, this, I suppose, is fair proof 

 of a likeness, provided one's sight is good. Such 

 a mistake I have made several times, and especially 

 upon one occasion. 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 accustomed 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. It was like a conjuring 

 trick. The broad, flat head, from which the short 

 beak projects hardly noticeably, presented no special 

 outline for the eye to seize on, but was all in one 

 line with the body. It looked just like the blunt, 

 rounded end, either of a stump, or of any of the pieces 

 of fir-bark that were lying about, whilst the dark 



