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IOWA ACADEMY OF SCIENCE Voi,. XXVII, 1920 
Fig. 64. This may be called a population density map, and becomes intelligible 
when superimposed upon the habitat map. 
explanation, because of the fact that the fence rows between grain 
fields did not seem to be especially rich in bird life. Of course 
the untilled strip between the fields was not as wide as that along 
the roads, nor did it, as a rule, contain as varied a group of plants. 
In these respects the roadsides would have an advantage. Be- 
sides these factors there might be mentioned the telephone poles 
along the roads which offered nesting sites to such birds 
as the Flicker and the Red-headed Woodpecker. The Dick- 
cissel also was very frequently seen perching on the telephone 
wires ; and it is possible that many of the numerous Dickcissels 
thus noted came to the wires from farther back in the fields. 
The same reasoning might also be applied to several other species 
as well. However, I do not think it can be denied that the strip 
of untilled and relatively undisturbed ground along the 
fence and road was so well adapted to nesting and feeding that 
birds were drawn to it. Perhaps the fact of greater density 
along the roadsides, as distinguished from the fence rows within 
the section, needs verification. This phase of the problem was 
not particularly in mind when the work was done. 
Table I gives a summary of almost all the data taken during 
the survey. The species are listed from top to bottom in order of 
their abundance. The crop and habitats are given at the top of 
