PICARIAN BIRDS. 93 



normal. To the former group belong our Common Nightjar (Capri- 

 mulgus europORus] (1216), a summer-visitor to Britain, and a bird 

 regarded with superstition by all European nations on account of its 

 supposed habit of milking goats, though its food consists exclusively of 

 moths, beetles, and such like. The peculiar "churring" sound uttered 

 by the male on summer evenings is familiar to most residents in the 

 country. Two other members of this genus, the Red-necked Nightjar 

 (C.ruftcollis) (1217) and the Egyptian Nightjar (C. agyptius) (1218), 

 have occurred as accidental stragglers to our shores. 



Among the more remarkable forms we may call special attention to 

 the African species Macro dipt eryx macrodipterus (1221) and Cosmetornis 

 vexillarius (1215) [PI. XVII. fig. 2], which carry ornamental wing-plumes. 

 In the former the ninth primary quill is enormously lengthened and 

 ends in a " racquet/' and in the latter it is even more extended, forming 

 a sort of train when the bird is flying. In Scotornis climacurus (1232) 

 from North Africa, and in the South American species of Hydropsalis 

 (1231) and Macropsalis (1214) some of the tail-feathers are greatly 

 lengthened. Nyctidromm (1228) is remarkable for the length of its 

 legs, and is more terrestrial in its habits than the other species, being 

 able to walk well. The Indo-Malayan species of Lyncornis (1229, 

 1230) have the feathers on the sides of the head elongate, forming 

 ear-tufts. 



The second subfamily includes certain Tropical American Nightjars 

 belonging to the genus Nyctibius, and represented by N. tether eus 

 (1233). These birds appear to breed in hollows of branches or stumps 

 of trees, and not on the ground, as is shown by the nesting-site of 

 N.jamaicensis (1234) exhibited on the floor of the Case. 



Family XII. CYPSELID^E. SWIFTS. (Plate XX.) 



The Swifts owe their trivial name to their extraordinary rapid flight, [Case 61.] 

 which is practically unlimited in duration, and in some of the species, 

 notably the spine-tailed forms of the genus Chaetura, is unsurpassed in 

 speed by any other bird. Though resembling the Swallows in their 

 outward appearance and habit of hawking insects on the wing, they 

 differ widely from these birds in important points of structure. They 

 are found all over the globe except in the extreme northern and 

 southern regions. Three subfamilies are recognised the Cypselinee or 

 true Swifts, the Chaturinte or Spine-tailed Swifts, and the- Macroptery- 

 ffince or Crested Swifts. In the first of these groups all four toes are 

 directed forwards, but in the last two the hind toe is said to be 

 occasionally versatile. Their toes, though well adapted for clinging, 

 are so small that walking is difficult, and these birds experience great 



