RENDAHL, BIRDS FROM THE PEARL ISLANDS. 15 



Undoubtedly we can separate the specimens, occurring 

 in the mainland in two head-groups, a greater northern one 

 and a smaller southern. To the first is to be referred B, v. vire- 

 scens Lin., B. v. frazari Brewst., B. v. anthonyi Mearns, and 

 B. v. eremonomus Oberh., to the second group B. v. mesatus 

 Oberh., b. v. hyperiiotius Oberh., and the Pearl Island 

 form B. v. margaritophilus Oberh. The characters of the latter 

 three subspecies are in comparison with those of the northern 

 group according to Oberholser a smaller size and paler 

 colour. The average measurements of the wing in males are 

 in the first group 196 — 181,1 (maximum and minimum 202 — 

 176), in the latter 173 — 166 (maximum and minimum 177 — 

 160). 



The characters, distinguishing the three southern races 

 from another are, however, verv less distinct, particularly 

 referring to average characteristics. 



About the Pearl Islands bird already Thayer and Bångs, 

 as said above, stated their agreement with specimens from 

 southern Central America. But about the material, the same 

 from which Mr. Oberholser recognized his subspecies from 

 the Pearl Islands, they remark, that the birds in colour present 

 the most astounding amount of individual variation. «In 

 fact», they say, «among the birds it is härd to find two alike.» 

 Further they call attention to the very great seasonal dif- 

 ference, and the fact, that in arid regions the bird bleaches 

 very fast. 



The characters by which the Pearl Island bird according 

 to Oberholser differs from the form occurring in southern 

 Central America are the following: 



Size: smaller. B. v. hyper/iotms, male, wing 173,1 (168 — 

 177), tail 63,4 (58,5—69,5), exp. culmen 60,7 (56—64), height 

 of bill 11,9 (11—13), tarsus 50,4 (46,5—53), middle toe 45,1 

 (43 — 48). B. v. margaritophilus, male, wing 166 (160 — 174,5), 

 tail 60,7 (56—66), exp. culmen 57 (54—60), height of bill 

 11 (10,5—12), tarsus 47,3 (44—49), middle toe 42,8 (40—45). 



Colour : 



Målar stripe. 

 Upper surface 



Plume-like feathers. 



B. v. hypernotius I B. v. margaritophilus 



Buff 



Deep bottlegreen, rather 



glossy. 

 More oily green, a little 



glaucous. 



Tawny ochraceous. 

 Deep bottle green, some- 



what glossy. 

 Glaucous and somewhat 



bluish. 



