1260 U.S. NATIONAL MUSEUM BULLETIN 23 7 part 3 



guess has remained consistent. In birds killed by shrikes or found 

 dead, dissection has proved the guess correct more often than not. 



Male wing and tail measurements average slightly longer than 

 female, and those of adults slightly longer than first-year birds of 

 the same sex, but with too much overlap to be used for certain sex 

 identification. 



Weights. — During three winters at Stillwater, Okla., I weighed 

 birds at the time of banding and at intervals throughout the season 

 on scales accurate to .065 grams. The 754 weights recorded for 200 

 individuals between November and May reveal definite weight 

 patterns for the species that can be correlated with age, migration, 

 molt, and seasonal temperature. 



Adult weights showed extremes of 28.4 to 48.8 grams and averaged 

 36.4 grams; immatures averaged 2 grams lighter at 34.4 grams, with 

 extremes from 26.2 to 44.9. Weights of individual birds varied up to 

 about 3 grams during the course of a day : lightest in the early morning, 

 heaviest at dusk. 



The seasonal trend was a rise from low weights on arrival in early 

 November to comparative highs during the cold months of January 

 and February, followed by a pronounced drop in March that lasted 

 through April into early May. The May averages increased con- 

 sistently and then soared sharply the last 2 or 3 days before departure. 

 Monthly averages showed adults varying almost 4 grams from a low 

 of 34.9 in March to a 38.8 gram high at departure in May; immature 

 monthly averages varied almost 5 grams from an April low of 32.2 

 to a departure high of 37.0 grams. 



Individuals not uncommonly varied as much as 8.0 to 8.5 grams 

 during their stay, more than 20 percent of their average body weight. 

 One small immature (presumably a female) that weighed 28.4 grams 

 when banded Apr. 21, 1950, gained 7.3 grams to 35.7 grams by May 11. 

 She returned the next fall, still classed as small at 32.3 grams. She 

 gained only a gram during January and February, and dropped back 

 to a normal 32.6 through April and the first fortnight of May. 

 Between May 14 and 18 she shot up 5.2 grams to 37.8, a gain of 16 

 percent in less than a week. Converted into human terms these 

 figures become spectacular — they compare to a woman of 120 pounds 

 putting on another 20 pounds in the week preceding a vacation trip. 



Food. — Food habits of the Harris' sparrows during their stay in 

 the United States were thoroughly studied by Sylvester D. Judd 

 (1901), who analyzed the contents of 100 stomachs for the U.S. 

 Biological Survey. He reports that these birds subsist chiefly on 

 vegetable matter, which constitutes 92 percent of the total food; 48 

 percent of the food is weed seeds including ragweed, smartweed, 

 knotweed, black bindweed, pigweed, lambs'-quarters, groin well, and 



