BIRDS OF NORTH AND MIDDLE AMERICA. 315 



Oytocoris] alpestris giraiidi Ridgway, Man. N. Am. Birds, 1887, 349. 

 0\tocorys] a[lpestris] giraudi Coues, Key N. Am. Birds, 5th ed., i, 1903, 507. 

 [Otocorys alpestris.] Subsp. 5 . Otocorys yiraudi Sharpe, Cat. Birds Brit. Mus. , xiii, 

 1890, 549 (Corpus Christi). 



OTOCORIS ALPESTRIS MERRILLI Dwight. 

 DUSKY HORNED LARK. 



Similar to 0. a. giraudi, but decidedly larger, back more broadly 

 streaked with dusky, and hindneck darker and more rufescent; still 

 more like 0. a. pratlcola (both in size and coloration) and sometimes 

 scarcely distinguishable," but dusky streaks of back, etc., usually 

 broader and blacker, and superciliary stripe usiially yellow; similar 

 also to 0. a. leucolscma but slightly smaller and much darker, with 

 ground color of upper j)arts grayer; differing from 0. a. strigata in 

 being decidedl}" larger, much grayer above, with streaks narrower and 

 dusky instead of black, and (usually) without yellow on under parts. 

 Adult female similar to that of 0. a. praticola but slightly grayer and 

 darker; sides of breast darker and conspicuously streaked with dusky, 

 and size slightly smaller. Young "not with certainty distinguishable 

 from specimens of praticola of the same age."'' (Intermediate 

 between 0. a. leucolxma and 0. a. strigata.) 



Adult ?«rtZ^.— Length (skins), 154-165 (159) ; wing, 98.5-106 (102.9) ; 

 tail, 64-72 (69); exposed culmen, 10-12.5 (11); tarsus, 20.5-22.5 

 (21.6); middle toe, 11-12 (11.5).^ 



Adult female. -Ajeiigih (skin), 136; wing, 94-102 (97.1); tail, 

 58.5-66 (62.8); exposed culmen, 9.5-12 (10.6); tarsus, 19-22 (21.2); 

 middle toe, 10-12 (IL-S).*^ 



Breeding in northwestern semiarid districts of the United States, 

 from northwestern Nevada (along base of Sierra Nevada) and north- 

 eastern California (Placer, Sierra Nevada, Plumas, Lassen, Modoc, 

 Shasta, and Siskiyou counties) tlii'ough Oregon and Washington east 



« This form is, like the Penthestes of nearly the same geographic area, another 

 example of the very close similarity of intermediates between a darker and a paler 

 form to one belonging to a widely separated geographic area. In the present case, 

 0. a. merrilli is intermediate in coloration between 0. a. strigata and 0. a. leuco- 

 lama, the former being darker, the latter paler; and intermediates between 0. a. 

 merrilli and 0. a. leucolaema are so precisely similar to 0. a. praticola of the Atlantic 

 States that if mixed with a series of the latter they probably could not be separated 

 without reference to the labels. On the summit of the Sierra Nevada, about Lake 

 Tahoe, birds of this genus have been taken which, while apparently 0. a. strigata 

 seem to be, according to Mr. Oberholser's views (Proc. U. S. Nat. Mus.. xxiv. 1902, 

 835, 836), merely intermediates between 0. a. merrilli and 0. a. rubea — another exam- 

 ple of the same sort of mimicry. (For remarks concerning the case of Penthestes atri- 

 capillus from the same region see Part III, p. 398.) 



bOberholser, Proc. U. S. Nat. Mus., xxiv, 1902, 834. 



c Fifteen specimens. 



