Food of the Crow, Corvus brachyrhynchos Brehm, in South-central KansasPlatt, Dwight R.
Science
Food of the Crow, Corvus brachyrhynchos Brehm, in South-central Kansas
Platt, Dwight R.
Crows
The study area is on the eastern edge of the Great Bend Prairie
physiographic province of Moore (1930). The climate is characterized by
moderate precipitation (ann. 30"), a wide range of temperature
variations, moderately high wind velocities, and comparatively rapid
evaporation. The summers are generally hot, and the winters are
moderately cold but are free from excessive snowfall. The weather during
the study period was unusually dry, and the summer temperatures were
above normal. A drought had begun in 1952, following the cool and wet
summer of 1951.
The study area includes the zone of transition from bluestem or
tall-grass prairie to the buffalo grass or short-grass prairie. The
principal farm crop in the study area is wheat. Sorghum grain, oats, hay
crops (especially alfalfa), and corn are also grown. The study area
supported a small population of breeding crows; an estimate based on
field observations mainly in eastern Harvey County, was not more than
one pair per square mile. In winter a large population of crows migrates
into the area from the northern Great Plains. Censuses showed that on
parts of the area the feeding population might be as great as 180 birds
per square mile. These wintering crows concentrate in the western part
of the study area where the flat, fertile wheat fields of central Harvey
County are replaced by sand dunes and the sandy Arkansas River Valley.
Here much land is devoted to raising livestock, and sorghum grain is an
important field crop. There is also more waste land there than elsewhere
in the area.
Data From Analysis of Pellets
Data obtained from the analysis of pellets were grouped in biweekly
collections, and percentages of various food residues in the pellets
collected within each biweekly period were averaged. Also frequency of
occurrence was computed, and maximum and minimum percentages were
included to permit a broader interpretation. In determining the minimum
percentage, only those pellets were considered in which the food residue
was present.
Pellets from roosts of resident crows were collected on a year round
basis in eastern Harvey County near Newton (see tables 1 and 2). The
data from these pellets were interpreted separately from data on
collections made in the western part of the study area from under roosts
of wintering crows (see tables 3 and 4).
In studies of the food of owls analysis of materials in regurgitated
pellets has been widely used, but with crows this method has been little
used because the nature of their food makes identification of material
more difficult. Analysis of pellets has certain merits, however, and, if
closely correlated with field studies, can give valuable information
concerning food habits. The availability of pellets and the ease of
collecting them are obvious advantages. Under large roosts in winter the
number that can be collected is almost unlimited. At other seasons,
pellets are scarcer, but even so they usually are more available than
stomachs.
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