Nightjar 119 



some 70 species, widely spread over the old and new worlds, and yet 

 the pectinated claw is found in all. Their surroundings, their habits, 

 and their food may vary, but the serration is always present. To 

 me, this seems strong evidence in favour of the claw being a vestigial 

 remnant from some bygone ancestor, which has long since lost its 

 original function, and is now, perhaps, of little service to these latter , 

 day descendants. 



Pectination of the claw is not confined to the Nightjars, but is 

 found in many widely separated birds, e.g., the Bittern, Gannet, 

 Heron and Courser. The wildest flight of imagination cannot lead 

 one to suppose that the purpose of the serration is the same in all 

 these birds.* 



There is not much difference in the plumage of male and female 

 Nightjars, but the male has a large, white spot on each of the first 

 three primarv quills, and has the two outer tail feathers on each 

 side broadly margined with white. In the female, these white 

 markings are absent. 



The Nightjar is rather a late arrival, seldom appearing before 

 the third week in April, and in some years not before the first days 

 of May. The bulk of them take their departure between the 20th 

 and 30tli of September, but I have seen an occasional bird as late 

 as the middle of October. 



Visitors, like the Nightjar, which arrive late and leave rather 

 early, are probably governed in their actions by the all-important 

 question of food supply. In this particular instance, the food 

 consists of large insects captured on the iving, especially nocturnal 

 moths and beetles. Nightjars are very voracious, though the body 

 is so small and light, and if food is not obtainable in sufficient 

 quantity, they will necessarily perish. 



The supply is uncertain in April, and again diminishes rapidly 

 towards the end of September ; the migratory movements are 

 dependent on this fact. 



By the middle of May, Nightjars are numerous on all the 

 commons and moorlands I have been speaking of. As the sun dips 

 in the west, their presence is manifested by the well-known jarring 

 or churring noise so familiar to every one. This sound, it is said, is 

 uttered b\- the male alone ; I have only shot two birds in the act of 

 churring, and both these were males. At first, one hears only one 

 or two birds, but as the twilight deepens, the concert becomes 

 general, and the loud whirring noise is heard from all quarters of 

 the common. 



If you will watch a bird — they are very amenable to observation 

 in the dusk — you see him perched, generally lengthways, but by no 

 means always so, on a branch of gorse or a thorn bush, or even on 

 a gate-post or convenient railing, churring loudly and almost 



•Against this "vestigial " theory is the fact that the pectination is not found in the 

 ncsthng, but develops later. Ancestral vestiges do the reverse, they appear in the embryo 

 and disappear in the perfect animal ; cf. the branchial arches in the mammalian embryo. 



