. Bulletin - Biological Survey. Zoology, Economic. do FOOD OF BOBOLESTK, 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 aguatica), 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 the}- 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 grasshopp
. Bulletin - Biological Survey. Zoology, Economic. do FOOD OF BOBOLESTK, 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 aguatica), 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 the}- 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. Fig. 5.—Diagram showing proportions of animal and vegetable food of red-winged blackbird in each month of the year. The relative amounts of the different kinds of food are shown by varioasly shaded , in Juno, useful insects arc 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 foo<l in similar manner. The percent- age of food (for example, of injurious insects), for a month, is not indicated by the summit of the curve, but by the space between the upper and lower cunes. (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 probalile 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, Avith a consequent reduction in the abundance of the species. The Biological Survey has examined stomachs of the redwing, collected in every month of the year, and trom thirty States, the District. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of th
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