BREWER'S SPARROW 1211 



these are sharp, well defined and concentrated toward the larger end. 

 The eggs of the two subspecies, breweri and taverneri, are identical to 

 one another and indistinguishable from those of Spizella pallida. The 

 measurements of 59 eggs average 17.0 by 12.6 miUimeters; the eggs 

 showing the four extremes measure 18.8 by 13.2, 17.8 by 14.7, and 

 15.2 by 11.4 miUimeters. 



Plumage. — D. K. Wetherbee (1957) described the downy tufts of 

 natal i)lumage as "light drab to drab gray" in coloration. Jean 

 Linsdale (1936b) in a study of heat exchange and color of nestUngs 

 recorded the color of the downy young as "dark, slate gray." The 

 Juvenal plumages of both breweri and taverneri are described in detail 

 by R. R. Graber (1955). According to him taverneri can be dis- 

 tinguished easily by the very heavy black streakings of the chest, 

 upper belly, sides and flanks. In breweri these areas are only hghtly 

 streaked. 



Brewer's sparrow^ starts losing the streaked juvenal plumage in a 

 postjuvenal molt soon after leaving the nest. H. S. Swarth (1930) 

 notes in taverneri that "Young in streaked juvenal plumage were out 

 of the nest by the middle of July, the postjuvenal molt was in progress 

 the later part of July and early in August, and birds in first A\inter 

 plumage, completely acquired, were collected by the middle of August. 

 An adult in the midst of the annual molt was shot August 6, and others 

 in fresh Avinter plumage tlu'oughout, on September 1 and 5," There 

 also is a partial prenuptial molt which, according to F. M. Chapman 

 (1910), "appears to be confined to the head, where there is a sHght 

 feather-growth, and one April specimen has been examined which is 

 acquiring new tertials, but the change to summer plumage is affected 

 chiefly by wear and fading." 



Ridgway (1901) states that the sexes are similar in coloration. He 

 gives the color of the bill in life as pale filaceous broAvn, darker at the 

 tip and along the culmen. Sometimes the maxiUa is blackish with a 

 pale commissure, and the mandible lilac grayish. The legs appear to 

 vary from pale brownish flesh to grayish horn color. Fuller and 

 Bole (1930) describe the iris as hazel in both sexes, and the female as 

 having a flesh-colored mandible and legs either "pale ])inkish dusky 

 flesh or pale horn color." 



Food. — Stomach analyses, supported by a minimum of field observa- 

 tions, indicate that Brewer's sparrow is a "beneficial" species sub- 

 sisting on a varied diet of plant and animal foods. The most thorough 

 study was conducted by E. R. Kalmbach (1914) in an effort to discover 

 the agents of natural control of the alfalfa ^^•eev^ Phytonomus poticiLS, 

 in which Brewer's sparrow may be important. He examined the 

 stomach contents of 46 Brewer's sparrows during the summer months. 

 In May weevils comprised 43.4 percent of the food and occurred in all 



