The Blue Grosbeaks 



3 or 4; pale bluish green, unmarked. Av. of 15 eggs from Arizona and California: 

 21.8 x 16.5 (.86 x .65). Season: May-July; one or two broods. 



Range of Guiraca ccerulea. — United States from Maryland, southern Illinois, 

 northeastern Nebraska, central Colorado, and northern California south to Chiapas, 

 Mexico, and in winter to Costa Rica. 



Range of G. c. lazula. — Breeds in the western states from Nebraska and western 

 Texas west (southerly) to the valley of the Colorado, south to Oaxaca, Mexico; winters 

 from southern Sonora to Costa Rica. 



Occurrence in California. — "Common summer visitant in the valley of the 

 lower Colorado River, from the Mexican line, north at least to Fort Mohave, above 

 Needles" (Grinnell). 



Authorities. — Morcom {Guiraca ccerulea), Bull. Ridgway Orn. Club, no. 2, 

 1887, p. 50 (Colorado R.) ; Grinnell, Proc. Biol. Soc. Wash., vol. xxiv., 191 1, p. 163 

 (crit.); ibid., Univ. Calif. Pub. Zool., vol. xii., 1914, p. 180 (Colorado R. ; occurrence, 

 crit.). 



No. 72b California Blue Grosbeak 



A. O. U. No. 597a, part. Guiraca caerulea salicarius Grinnell. 



Description. — "Similar to G. c. lazula of Arizona and Mexico in coloration 

 and general size but bill much smaller and proportionately less tumid, that is, outlines 

 straighter" (Grinnell, orig. desc). 



Range of G. c. salicarius. — California, except the Colorado River valley; winter 

 range not yet distinguished. 



Distribution in California. — Common, sometimes abundant in migrations 

 in southern half of State. Breeds chiefly in Lower Sonoran zone, locally in the San 

 Diegan district, and generally in the great interior valley north to Butte (Belding) 

 and Tehama (Red Bluff, July 22, 1916) counties; also in Owens Valley (George Creek, 

 May 19, 1919). Not found in winter. 



Authorities. — Heermann {Coccoborus coeruleus), Jour. Acad. Nat. Sci. Phila., 

 ser. 2, ii., 1853, p. 267; /. Mailliard, Bull. Cooper Orn. Club, vol. i., 1899, p. 44 (Santa 

 Cruz Id.); Ray, Auk, vol. xxiii., 1906, p. 404 (desc. nest); McAtee, U. S. Dept. Agric, 

 Biol. Surv. Bull., no. 32, 1908, p. 78, col. pi., part (food); Grinnell, Proc. Biol. Soc. 

 Wash., vol. xxiv., 191 1, p. 163 (Colton; orig. desc). 



ONE of the major fascinations of advanced bird study is the con- 

 firmation or readjustment of relationships. It is not enough to be told 

 by the taxonomist that a bird's relationships are such and such, because 

 of peculiarities of structure, similarities of wing formula;, etc. The state- 

 ment may be true, but we take it under advisement as a hypothesis, 

 and seek other evidences — evidences of song, behavior, association, and 

 nesting habits — in confirmation or in modification of the anatomist's con- 

 clusions. While structural evidence is of the highest authority, it requires 

 constant interpretation. Whereas the degree of change in the skeletal 

 structure, for example, may be determined by calipers, the rate of change 

 can never be known from physical appraisement. A knob on a bone, 



414 



