This helps smooth-out some of the variability in numbers of ducks seen from year to year and more clearly illustrates the chronology of the migration, irrespective of the changes in the magnitude. In the process of examining the migration chronology of various species, it became clear that some species of ducks could be grouped together for the purpose of illustrating their migration. Mid season divers include redhead, scaup and ring-necked ducks. Late season divers are goldeneyes and buffleheads. The numbers of mallards counted on the areas each week appears to have a disproportionate influence on the form of the migration curve for all ducks when mallards and other ducks are lumped together.
Mallards are conspicuous, refuge orientated, and relatively easy to count.
Each year, about half of all the ducks recorded on our refuges are mallards. Unless the climate has changed dramatically, however, this year s waterfowl season dates should encompass the primary migration period for the vast majority of the ducks that will be flying through Iowa.