The percentages are weighted toward the food items taken in summer and autumn, since many biweekly periods in late winter and early spring are not represented. Of the collecting periods represented, two were in spring, six were in summer, seven were in autumn, and three were in winter. Pellets collected at a number of different localities are averaged together as a percentage; consequently the figures obtainable do not necessarily represent the diet of any one group of crows. Nevertheless the percentages obtained by this method are perhaps valid as a general indication of the diet of the crows in this area.
In my samples, plant material amounted to 69 per cent of the indigestible residues. Similar percentages have been found in other studies, ranging from 57 per cent (Barrows and Schwarz, 1895:72) to 71.86 per cent (Kalmbach, 1918:43). The percentage of plant material was highest in the winter. In one collection from a wintering crow roost it amounted to 99.5 per cent. In December in eastern Harvey County it averaged only 85.3 per cent. The lowest percentage (20) was found in the first half of October in eastern Harvey County when grasshoppers amounted to more than half the diet. At this same time pellets collected from the wintering roosts contained 72.4 per cent plant material.
Percentages of the chief items in the total food residues, and (in parentheses) number of sampling periods in which each item was represented, are shown in the following list: wheat 23.2 per cent (20), sorghum 15.2 (16), oat 7.8 (8), sunflower 7.2 (8), corn 5.4 (12), brome 4.2 (5), other grass 2.4 (7), cherry 1.2 (2), beetle 13.3 (21), grasshopper 9.3 (19), ant .7 (3), miscellaneous insect .2 (2), mammal 2.6 (19), bird .8 (1), eggshell .5 (3), snake .1 (2), fish .9 (9), crayfish 2.4 (12), snail .2 (9).
Wheat is the "staff-of-life" of the crows in south-central Kansas and the percentage recorded in the diet in my study is much higher than the percentages found by other investigators. Wheat, being the principal crop in this area, was a readily available food. The fluctuations in the use of wheat were due to fluctuations in the availability of other foods that were preferred. In eastern Harvey County wheat consumption was 35.7 per cent of the diet in the latter part of July, and 49.1 per cent in December.
Consumption of wheat was high (34.4 per cent) during the harvest in June. However, this does not indicate serious damage since the crow population at this time was low, and much of the wheat eaten probably was shattered waste grain. When plowing began, wheat consumption was much reduced. At the time wheat was sown, September 10 to October 15, consumption was average to low.
In western Harvey County wheat was less important in the diet of wintering crows. After reaching a peak (22.7 per cent) in October, just after sowing, it steadily decreased, varying from 6.9 per cent to none in December.
The wheat consumption of crows has little significance economically. No instances of damage were reported to me either at the time of harvest or at the time of sowing. Although crows undoubtedly do eat wheat from newly sown fields, this utilization seldom damages the stand. No evidence of pulling young wheat was found. Most wheat eaten was waste grain.
Grain sorghum was the staple food of the wintering crows. In eastern Harvey County, where sorghum is not an important crop, its consumption began in August, reached a peak in the last part of November, and fell off sharply in December. The grain sorghum crop is vulnerable to damage by crows and it is ripening in the autumn as the crow population is building up. In certain areas and certain years the loss may be important. An exceptional instance was reported to me of crows taking 40 per cent of the crop from a small field of early ripening sorghum near a roost. Most farmers and county agents interviewed thought that the over-all damage was not great. The crop is usually combined and little remains in the fields after October, when the majority of wintering crows arrive. Nevertheless, even waste grain picked up after harvest should be counted as a loss on some farms where stock are turned in to clean up such grain.
Oats were taken sparingly as waste grain in summer, autumn, and winter, and most were eaten in late winter and early spring from newly sown fields (37.2 per cent of the February diet and 72.6 per cent of the April diet). These percentages were probably high, since there is a high proportion of indigestible residues in oats. This is more than compensated for in the yearly average by the paucity of collections made in the period when consumption of oats was highest.
Fields newly sown to oats provided a major supply of food in the early spring when other food supplies had been depleted. However, no instance of damage to a stand of oats was reported to me. Aldous (1944:294) mentioned that crows fed on spring-sown oat fields in Oklahoma but suggested that they picked up only grain which was not covered.