60 



NORTH AMERICAN FAUNA. 



Although Myadestes ohscuriix insidarin is very closely related to occi- 

 dentalis, yet it may be distiiiguislied by several slight but coustaut 

 characters, such as the greater exteusiou aud paler shade of ashy from 

 the neck over the forward part of the back. The lower parts also are 

 l)aler, especially on the throat and abdomen. The white tips to the tail 

 feathers, mentioned by Dr. Stejneger as characteristic of tins form, are 

 equally common on sjiecimens of occidentalis. 



The following- measurements show the relative size of the two forms: 



Measuremenla of Myadestes obscurna iuaular'ia and Myadestes o. occidentalis. 



Hyloclchla ustulata (Niittall). Riisset-backeil Thru.sh. 



A tyijical specimen of this species, taken on the islands by Colonel 

 Grayson iu the winter of 18115, is in the National Museum. In his 

 notes Colonel (rrayson says : " I found this little thrush in the month 

 of January quite abundant in the thickest of the woods of the Tres 

 Marias. It is very timid and shy, more so than any bird 1 saw upon 

 the islands; it frequently uttered a low, plaintive whistle, and seemed 

 solitary iu its habits." We saw none of them ou the islands in May, 

 and it is safe to class them as winter visitants. 



Hylocichla ustulata STwaiusonii (Caliaui.s). Olive-backeil Thrush. 

 Hylocichla ustulata ahnw Oberholser, Atik, XV, p. 304, October, 1898. 



Two specimens of this thrush were taken on Marie Madre, one on 

 May 5, the other on May 10. They were found in the heavy forest back 

 from the coast, and evidently occur only as stray migrants. 



Mr. Oberholser mentions these specimens as typical examples of his 

 subspecies, which is considered a synonym of Ht/lovichla u. swainsonU 

 by the American Ornithologists' Union. 



Merula graysoni Ridgway. Tres Marias Robin. 



Tnrdiis Jlainrostris Grayson, Proo. Boston .Soc. Nat. Hist., XIV, )>. L'Tfi, 1871 (part) ; 



Lawr., Hem. Boston Soc. Nat. Hist., II, p. 2G0, 1874 (pan). 

 Merula flavirostris grnysoni Ridgway, Proc. TI. S. Nat. Mus., V, ji. 12, 1882. 



Grayson's robin is one of the most abundant and widely spread resi- 

 dents and takes the place of M. flnvirostris of the mainland, which it 

 closely resembles in habits and general appearance. Although a char- 

 acteristic bird of tlie islands, yet occasional stragglers reach the main- 



