THYMUS GLAND— TICHICRO 961 



The Thrushes have been generally considered to form a distinct 

 Family, Turdidai, which is j)laced by some taxonomers the highest 

 in rank among birds. The fallacy of this last view is pointed out 

 elsewhere (Introduction). Though many modern systematists will 

 admit the close connexion of the Turdidai and some of the so-called 

 Family Sylviidse (Warbler), the abolition or modification of the 

 latter, by wholly or partially merging it in the former, has not yet 

 been satisfactorily effected. Mr. Seebohm {Cat. B. Br. Mus. v. p. 

 1), being compelled by the conditions previously laid down by Dr. 

 Sharpe {op. cit. iv. pp. 6, 7) to unite them, protested against doing 

 so. His own assignment of the subfamily Turdinx was into 11 

 genera, of which, however, 6 only would be commonly called 

 Thrushes, and it must be borne in mind that in establishing these 

 he regarded coloration as the most valid character. They are Geo- 

 cichla (a phantom name) with 40 species, Turdus with 48, Merula 

 with 52, Mimocichla with 3, Catharus with 12 and Monticola with 

 10. These last, well known as Rock-Thrushes, make a very near 

 approach to the Redstart (p. 775) and Wheatear. 



THYMUS GLAND, a body of obscure significance; but 

 wrongly called a gland. It is best developed in young birds, and is 

 a yellowish mass extending on either side from each bronchus along 

 the jugular vein and ending like a thread. In adults it becomes 

 much reduced and is not unfrequently lost. 



THYREOID GLAND, like the last, is of unknown function 

 and wrongly called a gland. It is a small, oval, reddish -yellow 

 body situated on either side of the root of the neck, loosely covered 

 by the skin and attached to the carotid artery and jugular vein. 

 In an adult Swan it is about three-quarters of an inch long. 



TIBIA, in common descriiDtive ornithology the third and 

 generally the longest portion of the Bird's leg, intervening between 

 the Femur and the so-called " Tarsus." For its actual composite 

 nature see Skeleton (p. 863). 



TICHICRO, the name (given from its note) in Jamaica of a 

 small bird, the Fringilla savannanivi of Gmelin, now referred either 

 to the genus Coturnicuhis, of which the very closely allied F. passerina 

 of Wilson, the YelloAV- winged Bunting of North America, is the type, 

 or to Ammodromus, founded for the Sharp-tailed Finch, A. caudacutus. 

 Both belong to a gi-oup of New- World forms hitherto ill defined, 

 and considered by some to be Finches and by others Buntings. 

 Of somewhat Lark -like habit, the Tichicro is said by Gosse {B. 

 Jam. p. 245) to have the habit of running on the ground, and to 

 perch but seldom, in Avhich respect it diff"ers from both norma) 

 Finches and Buntings {cf. Towhee). 



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