Juy1, 1$941 
PROJt Tt SK1RYWIM  RTES IN AR QRTM P8 
Cooperatort' National Park eServie (personnel) 
e* b.           h winter we census the pheasants (IV "riving* 
with x    O cew, usually In Deceber). The   onsus sie 1935 
is attahed, and shows a present popuation of about 300. 
ror the remainder of lhe winter we trap all the pheasants we 
can ban   each uabM bird, and rle&e in place. Drin           the 
average recent winter we maged to attach bwns to balf or two 
thirds of the pouation 
The unbaded birds eagt eah winter represent the new crp, 
plus a proportion of the unbanA.d adult residue from previous years. 
This proportioa can be ompled from the previous censues and badiangs. 
Thus we ean follow the shrinkge of ay year-lass through 
successive years. and draw a survival curve equivalent to an actuarial 
table for life-expct&y in hmn populations. 
s.          repeati   this operation  inec the winter of 1937-3  , we 
deduce that of 100 pheasants representing new crop on the Arboretum 
refugs in Dseeber 33 will survive until a year later 
10 will survive until two years later 
will survive until three years later 
These survivals determine a "regressive curve" heretofore aail-

able for only a few species, and never before for a gm bird. his 
regression is oe of the most fundamental characters in wildlife 
maa   *e. The shrings is mh faster than anyone anticipated. 
All this assumes the population to be self-contained, i.e., free 
from mch ingress and egress. Trappings last winter of 100 birds at