ZOOLOGICAL MUSEUM, TRING. 29 
tlie least allied to the Owls. There are a great 
number of foreign species, some of great beauty and 
with enormously elongated feathers either on the 
wing or tail ; while there is only one Central European 
species, our Caprimulgm europaeus, ih.e. Common Night- 
jar. The Podargidae occur from India to Australia. 
The Swifts ( Cgpselidae), represented in this country 
by the Common Swift, Apus apus (or more often — 
though less correctly according to priority^ — called 
Micropus apus), while two others, the Alpine Swift 
(A. melba) and the Needle-tailed Swift {Chaetura 
caudacuta), have occurred in exceptional cases, are the 
most powerful and swiftest fliers of all birds. Although 
generally of sombre colours, they are an interesting 
group in many ways, the most singular being the 
little swiftlets, or Collocaliae, of the East, which 
make nests, generally in caves and attached to the 
rocks, out of their own spittle, some being entirely 
formed of this material, others partly consisting of 
moss, rootlets, or weed, glued together and on to 
the rock with their spittle. The salivary glands of 
most Swifts are enormous, and also our Common 
Swift uses some of its saliva to fix its nest. 
Bird Case IV. 
contains, above, several groups of Picarian birds, as 
the Motmots or Momotidae, a neotropical family 
(genera : Momotus, Urospatha, Prionorhynchus, and 
others) ; the Rollers, Coraciidae, with only one 
