

| | o.o- 9.9 30.0-39.9 
10.0-19.9 40.04 
E—¥ 20.0-29.9 No data 
Fig. 4. Average numbers of mourning doves heard per route by 
physiographic region (after Dolton 1977). 
routes throughout the Nation (Dolton 1977). Each call- 
count route has 20 3-minute listening stations spaced at 
1.6-km intervals. At each listening stop, the number of 
doves heard giving the five-syllable perch coo are counted. 
The average numbers of birds heard calling per route pro- 
vide a year-by-year index to breeding dove population 
numbers. Although some problems of interpretation 
remain, these population indices are believed to be valid 
for detecting major changes in breeding population levels 
for management units and for determining long-term popu- 
lation trends for States and management units (Foote and 
Peters 1952; Baskett et al. 1978). This information is used 
by wildlife administrators to set annual hunting regulations. 
Importance of Breeding Areas 
Although mourning doves breed throughout the United 
States, certain areas contain higher densities of breeding 
doves than others. By using the average number of doves 
heard calling on the national call-count routes between 1967 
and 1975 (1967 and 1974 in the CMU), the respective den- 
sities can be illustrated for physiographic regions (Fig. 4) 
and States (Fig. 5). Generally, the highest mourning dove 
densities are found in “America’s Breadbasket” (Kansas, 
Nebraska, and Oklahoma), in the Sonoran and Mojave 
deserts of Arizona and California, and in the Piedmont area 
of the East. The lowest dove densities are in the forested 
areas of the North, Northwest, and Rocky Mountains. In 
the CMU, the States of the two easterly tiers clearly con- 
tain the highest breeding dove densities. 
The relative importance of various breeding mourning 
dove populations can be further illustrated by Breeding 
Population Indices obtained for each State. These indices 
were obtained by multiplying the average number of call- 
ing birds per route by the geographic size of the area where 
they are found (Appendix Table A-1). The CMU constitutes 
46% of the land area of the United States and contains 



| | o.0- 9,9 30.0-39.9 
110.0-19.9 40.0+ 
= 20.0-29.9 
Fig. 5. Average numbers of mourning doves heard per route by 
State (after Dolton 1977). 
about 56% of the breeding dove population. Furthermore, 
the mid-tier of the CMU States (North Dakota, South 
Dakota, Nebraska, Kansas, Oklahoma, and Texas) makes 
up only 21% of the United States land area, but contains 
about 36% of the Nation’s breeding doves. 
Central Management Unit 
Mourning Dove Habitat 
The CMU is characterized by a variety of habitat types 
because of its heterogeneity in elevation, topography, and 
climate. Elevations range from sea level along the Texas 
Gulf Coast to over 4,300 m in the Rocky Mountains. Tem- 
peratures vary from hot in the summer and mild in the 
winter along the Mexican border to cool in the summer and 
frigid in the winter in Montana and North Dakota. Annual 
precipitation in western Texas averages less than 20 cm, 
whereas that of the Texas Gulf Coast is more than 142 cm. 
Vegetation reflects the various altitudinal, climatic, and 
edaphic conditions found throughout the CMU. Natural 
climax vegetation still occurs over portions of the unit but 
much of the land has been modified greatly by the activi- 
ties of man, 
Habitat may be described by various standards, including 
its natural vegetation and its present use and composition. 
Perhaps the most useful system for describing potential 
vegetation is that devised by Kuchler (1964) and later 
modified by the U.S. Geological Survey (1970). The modi- 
fied Kuchler system includes 106 vegetation types, 60 of 
which are present somewhere in the CMU. 
For the present paper, the Kuchler vegetation types were 
consolidated into seven major groups (Fig. 6). The needle- 
leaf forests are in the upper elevations of the Rocky Moun- 
tains and northern Minnesota. The broadleaf forests are 
restricted to the eastern tier of CMU States, major river 
bottoms extending westerly to their headwaters, and a 
