28 THE CLASSIFICATION OF BIRDS 



the breast, no lateral bare tracts on the neck, and no interclavicular 

 process, to which must be added holorhinal nasals. The Scopidcc 

 and the Ardeidce differ from the Ibididce and the Ciconiidce in 

 having when adult the down confined to the bare spaces instead 

 of extending also over the feather-tracts as in all the other families 

 of the Ciconiiformes.* 



The Herodiones may be regarded as almost cosmopolitan, ex- 

 cept that their range does not reach the Arctic Regions, and that 

 of the Scopidce is confined to Africa. 



four pairs. In the Falconiformes they are found in a few genera of Psittaci and 

 Accipitres, but not in the Striges. In the Coraciiformes they appear in Podargus 

 and Hatrachostomus among the Caprimulgi, and in Leptosomus among the Picariae. 

 In the Passeriformes they are only known in the genus Artamus ; but in the Tur- 

 niciformes they appear to be always found in the Eurypygse (five pairs) and in 

 the Crypturi. They are unknown in the Galliforrnes, Apterygiformes, Struthioni- 

 formes, Sphasnisciformes, Kalliformes, Charadriiformes, Cathartiformes, Trogo- 

 niformes, Piciformes, or Cuculiformes. 



* The difference between a Sparrow, a Cormorant, and a Duck in their 

 immature dress is very remarkable. The young Duckling is hatched with a thick 

 coating of soft down. The Sparrow and the Cormorant come out of the egg as 

 naked as frogs. In a very short time the Cormorant grows a coat of down as 

 thick and soft as that of the young Duckling ; but the Sparrow has evidently 

 come to the conclusion that with his snug feather-lined nest and devoted parents 

 always ready to protect him from cold in bad weather, it is not worth his while 

 to acquire a complete dress of down, and is content to wait patiently for his 

 feathers. The amount of down which is acquired before the feathers arrive varies 

 according to the habits of the species, and the same may be said of the amount 

 of down which is retained in the adult plumage. The Sphjeniscomorphse and 

 the Pelargomorphte have for the most part so far deviated from the primitive or 

 typical bird as to adopt an aquatic life. Apparently, in order to suit themselves 

 to these conditions they have found it " fit " to retain a certain amount of down 

 under their feathers throughout life. The only exceptions in these two subclasses 

 are the following families, which may possibly be reverting towards the primitive 

 type by becoming less aquatic in their habits. The Scopidce, the Ardeidce, the 

 Strigidce, the Otididce, and the Pterodidce have discarded the down from their 

 feather-tracts, but have retained it on the bare spaces, whilst the Columbidic have 

 "gone one better " by discarding the down from both. In the remaining thirty 

 families there is more or less down distributed both on the feather-tracts and on 

 the bare spaces of the adult. 



The ^Egithomorphse, the Coraciomorphae, and the Dromajomorphae contrast 

 strikingly in this respect with the Sphseni^comoiphje and the Pelargomorphse. 

 The Dromseomorphae lose all their down when adult. The only families in these 

 three subclasses which retain it both on the feather-tracts and bare spaces are 

 the Cathartidce, the Alcedinidce, the Eurypyyidce, the JRhinochctidcc, the Cariamidce, 

 the Psophiidce, the Opisthocomidce, and possibly the Mexitidce. A few families 

 take an intermediate position, having down more or less sparingly distributed 

 over the bare spaces, but not on the feather-tracts : these are the three families 

 which compose the Caprimulgi, the Cypselidce f the Cuculidce, the Turnicidce, the 

 three families which compose the Galli, and, it is said, some species of the Pas- 

 seridcc and Tyrannidce. In the remaining eighteen families it is not known that 

 the down is retained in any part of the plumage of the adult. 



