Food of the Crow, Corvus brachyrhynchos Brehm, in South-central Kansas

by Dwight R. Platt

A female insect eaten before oviposition has a greater ecologic significance than one eaten after she has laid her eggs and is ready to die.

Beetles made up more than half of the insect component of the diet. Scarabaeids were readily recognizable. Other beetles were classified as predaceous or non-predaceous according to the type of mandibles found. When mandibles were lacking the occurrences were listed merely as unclassified beetles, and those made up 5.6 per cent of the yearly food residues. Predaceous beetles made up 3.3 per cent, whereas non-predaceous beetles made up only 1.3 per cent. Both were found in one-half of the collecting periods. Predaceous and non-predaceous beetles formed 1.2 per cent of the yearly food residues. This preponderance of predaceous beetle material is what might be expected from the manner in which crows feed. Many predaceous ground beetles of the family Carabidae would be found under rocks and clods and on the ground.

Beetles were a constant component of the diet in summer. They reached a peak of 48.7 per cent in the last part of July. In November the percentage declined and by December they formed only 2.5 per cent of the diet.

Scarabaeid beetles were utilized in large quantities when they were most abundant; they made up 28.7 per cent of the diet in the latter part of June. The larvae of scarabaeid beetles are destructive to wheat and alfalfa and live in the ground from one to three years before metamorphosing into adult beetles. Adults emerge from the ground from April to mid-August, the maximum flight occurring in May and June. Most of the eggs are laid from the last of May to the middle of July (Hayes, 1920:306). Afterward the adults soon die. Many of the beetles are nocturnal, but some of the more important destructive forms are diurnal (Hayes, 1918:142). Crows pick up the diurnal forms when they are active and perhaps find the nocturnal forms under clods or in burrows and eat them in ecologically significant numbers.

Crows are beneficial to the farmer insofar as they control the populations of scarabaeids and other non-predaceous beetles. However, destruction of predaceous beetles is harmful to the farmers' best interests.

Grasshoppers, second only to beetles in the insect component of the diet, are among the most destructive insects in Kansas. Eggs laid in autumn overwinter and hatch the next summer, from April to August, depending upon the species. The maximum numbers of grasshoppers are present in late summer and early autumn and they continue feeding on crops until the first killing frost. The greatest damage is caused by the destruction of the foliage of corn, wheat, and alfalfa (Smith, et al., 1943:126). The consumption of grasshoppers closely followed the curve of their availability, since they are a preferred food of the crow. They were picked up in small quantities even in winter. In summer they made up 6 to 10 per cent of the diet of the crows in eastern Harvey County. Through the late summer and autumn this percentage rose, until during the first half of October they made up 59.6 per cent of the diet. However, in the western part of the study area, they constituted a smaller part of the diet.

Predation upon grasshoppers, especially in summer and early autumn, benefits the farmer by helping to stabilize populations of grasshoppers. However, when grasshopper consumption was highest, in early October, many of those eaten probably already had completed their breeding cycle, and their consumption was hence of little significance economically or ecologically.

Ants were consumed only in September and October when they constituted as much as 14.9 per cent of the diet. Crows may make an entire meal from a large colony; at any rate, whenever ants were found in a pellet, they constituted a large percentage of it.

Miscellaneous insect remains constituted two-tenths of one per cent of the yearly diet. Hemipteran remains were present only in trace quantities (.5 per cent of the July 13-26 sample from eastern Harvey County).

Only a few questionable fragments from insect larvae were found in the pellets collected in the course of this study. However, as mentioned earlier, there is evidence that larvae constituted a major food supply during much of the summer.