THE BIRDS 



NORTH AND MIDDLE AMERICA. 



By Robert Ridgway, 



Curator, Division of Birds. 



Part IV. 



Family TURDID^. 



THE THRUSHES. 



Slender-billed or small-billed, ten-primaried aciitiplantar Oscines, 

 having the acrotarsium undivided or "booted," except for lower por- 

 tion, and the young in first plumage more or less distinctly spotted 

 above as well as below, '^ even in species which are unspotted in the 

 adult stage. 



The preceding brief diagnosis is sufficient to distinguish the Tur- 

 didsd, as usually restricted, from the most nearly related groups of 

 slender-billed, ten-primaried Oscines, with the single exception of 

 the so-called family Muscicapidse (Flycatchers), an exclusively Old 

 World group, with which the Turdidse are nearly if not quite con- 

 nected by the Palsearctic genus Pratincola and related groups, the 

 Hawaiian genus Phseornis, the genera of the American so-called Mya- 

 destinse,^ and other transitional forms. In fact, no satisfactory line 



a In some of the Neotropical species of Planesticus, in several species of Catharus, 

 and in the Antillean genera Mimocichla and Ha-plocichla the young are very indis- 

 tinctly spotted, the spotting being confined on some of them to the under parts. In 

 the young of Zeledonia there is no trace of spotting in any portion of the plumage, and 

 the same may almost ])e said of the young of Catharus gracilirostris. Tlie value of this 

 character as diagnostic of the Turdidse is therefore much less than has generally been 

 supposed. (See remarks with reference to Phainoptila, under Family Ptilogonatidae, 

 on page 113, Part III, of the present work.) 



b The genus Myadestes grades so completely into Planesticus, through genera of vari- 

 ously intermediate structure that, unless osteological or other anatomical characters 

 may be found, it certainly cannot properly be considered as representing a group of 

 subfamily rank. 



11422— VOL 4—07 1 



