“The difference in age ratios between birds found dead and those reported 
shot cannot be considered conclusive. 
Table 22.--Monthly Variation in een genet a pa Reported for Black- 
crowned Night Herons 
Nestlings banded through 1941 and reported to 1946. Not shown 
here are 2 birds for which the month of recovery was uncertain, 
4 killed by automobiles, 23 caught in mammal traps, and 57 
caught sick, injured, or at fish hatcheries, 
a b c e Total Tota 
Month ound Dea ~ Reported Shot in in 
“tn intater in in Later First Later 
lst Yr. Years Total 1st Yr. Years Total Year Years 
vir (5)/ ew (5)i/ ig - (5)2/ - 
VIII 25 5 30 9 1 10 3h 6 
TX ly h 18 9 h, 13 23 8 
x 18 3 21 19 h 23 37 7 
XI sal mee __ i Sh Pe Seeckk. Jaden ted _ . 16 A eo 5 
Subtotal 7F_ G1z 69% “18E ~~ 32% 61% 19% — 37% 
XII - 5 2 7 10 y) 
I h 3 7 3 2 5 7 5 
II 3 3 6 1 3 h mM 6 
ITI 2 1 3 1 2 3 3 3 
Iv 1 5 6 - \ 4 1 9 
V 1 1 2 2 1 3 3 2 
VI 1 4 5 2 4 6 ; 
1 3 h 7 a 
VII 
Subtotal 21% ~~ 59% ~ — 55 ia Si 5) 39% -- ny - a3 
Total o7 34 121 oh 37 TOL 
Age Ratio 72% 28% 100% 6L 37% «21014. 68% 32% 
a month or so r banding. In 2 cases the young s own 
to another state. These 5 are not counted in the totals or per- 
centages here. 
Composite life tables 
An abridged life table for night herons covers at least 13 
years (table 23) and discloses an adult mortality rate of about 31 
per cent per year compared to about 61 per cent for juveniles. 
These same data were also set up in enother life table (not shown 
here) that yielded a mortality rate of 52 per cent between the first 
August 1 and December 31 and a mean rate of 30 per cent per annum 
for all years thereafter. This value of 30 per cent implies an 
adult mortality rate of about 2.5 per cent per month--a figure to 
which we will return shortly. 
58 
