Mortality and survival rates.--Over a 3-year retrappirg pericd, 
S. H. Low got a much higher survival rate (60 per cent per year) on Cape 
Cod, than I calculated fcr doves (2 per cent)in this study. There is no 
bias in his work that I can detect, and aside frem sampling limitations 
his result must be accepted as indicative of how widely survival rates 
may differ when calculated for a real population and for the theoretical 
ones examined in my own study. Low's results imply that, during the 
pericd he was retrapping, mourning dove populations on Cape Cod required 
an age ratio of only 0.67 young per adult to keep them stable. There 
is perhaps some implication that this species was locally increasing 
at the time of Low's study. Austin's recent (1951) calculation of a. 
mean mortality rate of 52 per cent per year for adult doves on Cape 
Cod is much closer to the results of my own study. This first-year 
mortality rate of 75 per cent is notably higher. 
Among the disappointments associated with my own work on 
doves was the impossibility of calculating mortality rates for northern 
and southern portions of the mourning dove population. This must 
clearly wait until more data are available. The work analyzed here 
also fails to give any clue as to the actual extent of mortality 
encountered by young birds fledging after September 1. One possible 
approach to this problem perhaps could be undertaken by a study of 
recovery rates with particular reference to reports of banded birds 
turned in by hunters. 
Summary 
Banding work on 9929 juvenile mourning doves has yielded 
recoveries of the order of 3.7 per cent, most of the reports coming 
from hunters. In this species, about 50 per cent of active nests hatch, 
each with 1.7 - 1.8 young. First-year mortality rates for young birds 
banded and alive on September 1 have run about 62-6), per cent, the 
mean adul*+ rate being close to 56-58 per cent per year. 
Dates of banding for 318 young in the Fish and Wildlife Ser- 
vice recovery files closely approximate the monthly frequency of hatch- 
ing dat-~s estimated for juvenile birds bagged in Texas during the fall 
of 19,9 as well as the seasonal spread of daily nesting activity cal- 
culated for Cass County, Iowa, by McClure, 18 per cent having been 
marked by June 1, 6 per cent by July 1, 71 per cent by August 1 and 
53 per cent by Sept. 13 these suggest that a minor fraction (hatching 
after September 1 and amounting to perhaps 10 per cent) of the juveniles 
were excluded from this study. For at least this section of the popu- 
lation, an age ratio of only 1.6 per adult as of September 1 seems 
necessary on the average to keep mourning deve populations in balance. 
107 
