Unchecked hunters reports of adult mallards banded in 1926-34 on the Pacific coast and shot in some subsequent year are grouped together to show the results of two different methods of calculating annual mortality rate. When such rates involved less than 100 alive at the start of an age interval, they were not calculated in this report (Hickey 1952).
Age Interval (yrs) x |
Number shot dx |
x+1 to x+2 | 845 |
x+2 to x+3 | 284 |
x+3 to x+4 | 124 |
x+4 to x+5 | 72 |
x+5 to x+6 | 29 |
x+6 to x+7 | 29 |
x+7 to x+8 | 12 |
x+8 to x+9 | 7 |
x+9 to x+10 | 5 |
x+10 to x+11 | 3 |
x+11 to x+12 | 1 |
TOTAL | 1411 |
Age Interval (yrs) x |
Alive at Start lx |
Number of Deaths dx |
Mortality Rate (%) qx |
x+1 to x+2 | 1411 | 845 | 59.9 |
x+2 to x+3 | 566 | 284 | 50 |
x+3 to x+4 | 282 | 124 | 44 |
x+4 to x+5 | 158 | 72 | 46 |
x+5 to x+6 | 86 | 29 | - |
x+6 to x+7 | 57 | 29 | - |
x+7 to x+8 | 28 | 12 | - |
x+8 to x+9 | 16 | 7 | - |
x+9 to x+10 | 9 | 5 | - |
x+10 to x+11 | 4 | 3 | - |
x+11 to x+12 | 1 | 1 | - |
TOTAL | 2618 | 1411 | mean = 53.9* |
Age Interval (yrs) x |
Alive at Start l'x |
Calculated Deaths d'x |
Mortality Rate (%) q'x |
x+1 to x+2 | 845 | 561 | 66 |
x+2 to x+3 | 284 | 160 | 56 |
x+3 to x+4 | 124 | 52 | 42 |
x+4 to x+5 | 72 | 43 | - |
x+5 to x+6 | 29 | 0 | - |
x+6 to x+7 | 29 | 17 | - |
x+7 to x+8 | 12 | 5 | - |
x+8 to x+9 | 7 | 2 | - |
x+9 to x+10 | 5 | 2 | - |
x+10 to x+11 | 3 | 2 | - |
x+11 to x+12 | 1 | 1 | - |
TOTAL | 1411 | 845 | mean = 59.9* |
* The mean mortality rate per annum is always the most statistically reliable mortality rate in an avian life table.
Updated 02 August 1999