PICARIAN BIRDS. 93 
normal. ‘To the former group belong our Common Nightjar (Capri- 
mulgus europeus) (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. ruficollis) (1217) and the Egyptian Nightjar (C. egyptius) (1218) 
have occurred as accidental stragglers to our shores. 
Among the more remarkable forms we may call special attention to 
the African species Macrodipterx macrodipterus (1221) and Cosmetornis 
vevillarius (1215) [Pl]. XIX. 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 (1282) 
from North Africa, and in the South American species of Hydropsalis 
(1231) and Macropsalis (1214) some of the tail-feathers are greatly 
lengthened. Nyctidromus (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. ethereus 
(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 (1284) exhibited on the floor of the Case. 
Family XII. Cyrseniva. Swirts. (Plate XX.) 
The Swifts owe their trivial name to their extraordinary rapid flight, 
which is practically unlimited in duration, and in some of the species, 
notably the spine-tailed forms of the genus Chetura, 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 Cypseline or 
true Swifts, the Cheturine or Spine-tailed Swifts, and the Macroptery- 
gine or Crested Swifts. In the first of these groups a// four toes are 
directed forwards, but in the two latter 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 
[Case 61.) 
