PERCHIXG-BIRDS. 115 



Section B. ACROMYODI. Singing-Birds (p. 107). 



Family I. Atrichornithid.55. Scrub-birds. 



S L Only two small Australian species of the genus Atrichornis {\i(i\) [Case 71.] 

 are included in this family, peculiar among Passerine birds in having 

 the clavicles (merry-thought) rudimentary. The wings are so small 

 that their powers of flight are limitedj and they live among the dwarf- 

 ferns and dense thickets^ where they are only to be detected by their 

 noisy note. 



Family II. Hirtjndinid.^;. Swallows. 



This well-defined cosmopolitan family, formerly associated with the [Case 71.) 

 Swifts {Gypselidae) on account of their similarity in general appearance 

 and habit of hawking insects on the wing, are now recognised as 

 belonging to the Passerine Birds. The long powerful wings, feebly 

 developed feet, small flattened bill and wide gape are the most striking 

 external features, possessed in common with the Swifts ; but the latter 

 may always be distinguished by having 10 instead of 13 tail-feathers. 

 The anatomical differences between the two families are many and 

 striking. Many of the Swallows breed in colonies, and two or even 

 three broods are reared in a season. About 116 species are recognised 

 and divided into two subfamilies — the Hirundinints, including the true 

 Swallows and Martins, and the Psalidoprocninm, or Rough- winged 

 Swallows (1815), in which the outer margin of the first flight-feather is 

 provided with hooked barbs. 



Of the former the Common Swallow (Hirundo rustica) (1808) is 

 typical, and one of the most familiar and beloved of our summer visitors. 

 It ranges north in summer over Europe and Asia, extending beyond 

 the Arctic Circle, and winters in South Africa and the Malay Peninsula. 

 Many other species are equally migratory, and traverse immense 

 distances on their periodical journeys. Two other well-known visitors 

 to the British Islands are the House-Martin {Chelidon urbica) (1802), 

 which builds mud nests under the eaves of houses and on the ledges of 

 cliff's, and is easily recognised by its feathered toes; and the Sand- 

 Martin [Cottle riparia) (1805), which excavates a tunnel in a bank 

 terminating in a nesting-chamber. Both these birds lay pure white 

 eggs, but those of the Swallow are spotted with reddish brown and 

 lavender-grey. 



Family III. MuscicapidjE. Flycatchers. 



This somewhat vaguely defined family includes a very large number [Ctuse 71.] 

 of insect-eating species peculiar to the Old World, and may generally be 



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