38 FOOD OF BOBOLINK, BLACKBIRDS, AND .GRACKLES. 
The increase of vegetable food other than grain and weed seeds 
during August and September is due to the consumption of wild rice 
(Zizania aquatica), which at this time forms quite an important item. 
In their insect diet the redwings do much good, for only a small 
proportion of the species they eat are beneficial. More destructive 
snout-beetles (weevils) are eaten by them than by any other birds that 
the writer has examined, with the single exception of the bobolinks. 
Other beetles and grasshoppers also constitute an important part of 
APR|MAY |JUNE|JULY | AUG.|SEPT] OCT. | NOV. | DEC. és 
400 SERN SS NANS RON RRA PARANA ES 
SME BATAR YS SNS QASATSS SABES SQL 
SSAA SSS SRS 
90 SSUES NRE ' 
ARS ANY AYSNA\S SNS) ry 
SSRIS 
RASA SSAS AY YS ARS 
SASS PSN SANSA < 
BO fs ASS 80 
he NS AN 
i} AW SS 
E EAN 
70S YE ASS 70 
60 60 
VX NSS 
50 50 
40 Nis 
URIOUS—=INSECT: 
50 30 
10 40 
Fig. 5.—Diagram showing proportions of animal and vegetable food of red-winged blackbird in 
each month of the year. ‘he relative amounts of the different kinds of food are shown by variously 
shaded areas. Thus, in June, useful insects are represented by the broken-lined area at the bottom 
of the column for that month, injurious insects by the horizontally shaded space, grain by the space 
shaded with diagonal broken lines, and the other elements of food in similar manner. The percent- 
age of food (for example, of injurious insects), for a month, is not necessarily indicated by the summit 
of the curve, but by the space between the upper and lower curves. (The figures in the margins 
indicate percentages. ) 
the insect food. While there can be no doubt that the birds do con- 
siderable damage when collected in large flocks, it is probable that 
such injury will become less and less as the area of cultivation 
increases and the swamps where they breed are encroached upon and 
drained, with a consequent reduction in the abundance of the species. 
The Biological Survey has examined 1,083 stomachs of the redwing, 
collected in every month of the year, and from thirty States, the District 
