E colog y and M anagemen t of Squirre ls - W-66-R 
C. M. Nixon , 
L. P. Hansen 
Whereas hickory seed supplies some food for a variety of wildlife species, 
food habits studies have shown that, for Midwest squirrels, the hickory nut 
ranks as the 1st choice food in late summer and fall. At this time, squirrels 
are rapidly gaining weight, and hickory nuts, high in fat and very digestable, 
are important in improving the physical condition of squirrels before winter. 
Seventy or so years ago, hickories were highly valued because the great 
strength of hickory wood was essential for the manufacture of wagon parts. 
Indeed, there was concern that quality hickory was being depleted through over¬ 
cutting in much of the eastern United States. With the advent of the automobile, 
the demand for and value of hickory wood declined to the point that, until 
recently, the hickories were considered weed species, to be culled from the 
forest at the earliest opportunity. 
Wildlife managers who wish to increase the amount of seed-bearing hickory 
must consider the silvicultural requirements of the genus. Hickories are 
relatively tolerant of shade and seem to increase best under light cutting, 
wherein the canopy remains intact and the faster growing intolerants are unable 
to take over in the understory. Hickories are slow growers throughout life, 
compared with their hardwood associates, and are frequently relegated to an. 
intermediate or suppressed crown position. The switch from light or selection 
cutting, where only small holes were made in the canopy, to complete clear 
cutting has made it difficult to culture them, particularly on the better sites 
(site index 70+). 
One cultural method, which might help overtopped hickory stems reach the 
canopy in clear-cuts, would be to crown-release suppressed hickories in clear 
cuts <20 years old. To provide data on which to assess the merits of crown¬ 
releasing hickory, we selected seedling sprouts of pignut, shagbark, and 
mockernut hickories growing on good (site index for black oak 70+), medium 
(site index 55“70), and poor (site index 55~&0) sites in stands clear-cut 6, 
8 , and 15 years before. Stems of each species were paired by height and stem 
diameter and 1 stem of each pair was selected for crown release by coin flip. 
A comparison of height and stem-diameter growth between released and control 
stems after 5 growing seasons showed that stem-diameter growth was consistently 
better for released stems for all 3 species. Height growth was not consistently 
related to treatment. However, when growth rates for released and control stems 
were compared after 3 growing seasons and then for the combined 4th and 5th 
growing seasons, a different picture emerged. Released stems of mockernut grew 
slower in height compared with controls the first 3 years after release but 
faster than the controls the 4th and 5th years after release. A similar pattern 
was also observed for pignut on one site. Of some concern was the reduction 
in stem-diameter growth rate shown by virtually all stems the 4th and 5th years 
after release, reflecting an increase in crown competition as surrounding trees 
closed in around the released stems. 
