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.
Return to Lecture Notes IV. Estimation of Population
Parameters - II. 
Updated 02 August 1999