I
tbrarr 
 
                                                         May 14, 1947. 
       CO    TS Olt THE DISAPPLARANCE OF 1ILLIONS OF WATJ RFOL FROY ONE 
             TO                     ACCOT     FOR BY LWAL KILL 
 Leopold et al -4as shown that the life span of the pheasant is three to
four 
                 years and that the juvenile component of a fall population
is 
                 about 70%. 
 Roy N. Bach .-has confirmed these results in North Dakota and derived certain

                 principles which I believe are applicable to waterfowl for
the 
                 following reasonesa 
 Ducks Unlimited's banding studies of waterfowl indicate a similar life 
 expectancy for ducks, namely tee to four years. 
 Ducks Unlimited's brood countd'0averare six per female, hence post breeding

 population. are coýposed of about 70,'     eniles, 
      Bach's principles are therefore as valid for waterfowl as for pheasants.

 They are quoted (in part) below. 
 
      1. "These 'ercentages vary seasonally and will depend largely
upon the 
 nestinL successos for any particular nesting season." 
 
      2. "Any given population (of North Dakota pheasants) Nould not
last much 
 longer than three years, if not replenished by new broods." 
 
      3   "Natural die-off is much higher than we uight at first expect
and th, 
 rate of natural die-off is proportional to the size of the population."

 
     4. "The natural rate die-off, however, is not constant over the
three 
major years in pestion. The rate (in bird lose per day) is highest durinG

the first yar.- 
 
     5. "Any factors which might seriously affect nesting successes
for a 
period of two years would seriously and drastically reduce our pheasant 
population no matter what that population had been to start with," 
 
     6. "The pheasant population in North Dakota depends almost entirely

upon the success of the nestinG season each year." 
 
     7. "The overall picture is one of a very short-lived or traasient

comodity, It appears to be a resource that cannot be saved for very loug.

If this study points to one major principle it is thist Provided that the

population is not too low, the largest harvest practicable should be made
of 
our pheasant during the fall imnediately followIng a successful nesting 
season*" 
 
     The basic facts from which these princippls are derived have been 
established for waterfowl and, in ir opinion, are equally applicable to them.

     Reference to the attached chart of waterfowl populations reveal that

1941 and 1942 showed a tremendouE upsurge in numbers (F. & W.S. estimates),

folloyd in 1942 and 1943 by similar upsurges in D.U. post breedinG estimates.

This reflected a healthy return of breeding stock, successful breeding seasons

and reduced hunting pressure.