Where Your Mallards Originate; The Truth about Band Returns

There are two ways to interpret banding data.  Only through ‘harvest derivation’ can hunters determine where their ducks really came from.

By Joel Brice - Manager of Conservation Programs

What waterfowler hasn’t held a drake mallard in hand and wondered about its life?  How old was the bird?  How many places had he been?  Where was he hatched?

The answer to that last question has far-reaching implications, not only for hunters but for waterfowl managers as well.  Understanding where the ducks we kill originated tells us where our conservation dollars will have the most impact.

That’s one reason waterfowl managers devote so much time, money and energy banding migratory birds.  Band returns provide a wealth of valuable information about the often mysterious birds. 

Interpreting banding data is a bit trickier than it seems.  Even if half or more of the ducks killed in your state were banded in a particular state or province, that wouldn’t necessarily mean that most of your ducks originate there. Why?

Banding effort—the number of ducks banded in a particular area—is but one reason raw banding data is unreliable for hunters searching for the source of their ducks.  Here’s an example: In 2002, about 1.2 million breeding mallards settled into North Dakota and 500,000 in Manitoba.   Common sense would suggest that from the mallard Class of 2002, North Dakota would produce far more band returns than Manitoba.

In reality, band returns from Manitoba would out-pace North Dakota by a substantial margin.  How can that be?  Because Manitoba crews captured and banded slightly more than 10,000 mallards that year, as opposed to just 2,399 mallards banded in North  Dakota.  Thus, as far as the 2002 banding season is concerned, hunters from Minnesota to Louisiana were almost five times more likely to kill a mallard banded in Manitoba than one banded in North Dakota.

If you really want to identify the source areas for the ducks you harvest, then harvest derivation is what you’re looking for.  Harvest derivation tells you what percent of your state or provincial total harvest comes from each region of the breeding grounds. 

Harvest derivation starts with banding data, but only the ducks that were banded from July through September.  Although it may not be where they were originally hatched, it’s assumed that ducks banded during this short window of time actually bred that year in the general area in which it was captured. 

Since ducks don’t recognize political boundaries, the source areas of harvest derivation are typically identified as regions, or band reference areas, rather than the fixed borders of states or provinces. 

Back in 1972, the US Fish and Wildlife Service outlined 16 different band reference areas.  The borders of each reference area were established based on the migration patterns of each region, meaning that the ducks in each reference area tend to exhibit different migration patterns from the others. 

For example, the ducks in southwestern Saskatchewan tend to exhibit different migration patterns from those in southeastern Saskatchewan.  A few other examples of band reference areas include southwest Manitoba, the Great Lakes (portions of Minnesota, Iowa, Illinois, Ohio and all of Wisconsin and Michigan) and the Missouri River Basin (comprised of portions of North Dakota, South Dakota, Minnesota, Iowa and Nebraska). 

Thinking in terms of regions makes more sense than political boundaries.  Most waterfowl managers and non-government waterfowl organizations, focus their dollars on regions rather than entire states or provinces. 

Since only a small percentage of the ducks in each reference area are banded each year, harvest derivation tells you how many ducks in the total population each band represents. 

Before scientists can do that, they must first correct for a few variables.  For each band reference area, the following variables must be considered: total population size, banding intensity (number of bands applied per species), percentage of male and female ducks (typically more drakes than hens in the population) and the percentage of adults and juveniles in each population (age ratios).  Age ratios are an important correction, since juveniles are more vulnerable to hunter harvest than adults.  Once these factors have been taken into consideration, now we’re comparing apples to apples. 

Harvest derivation for mallards was first calculated in 1982 by the US Fish and Wildlife Service and later updated by David Zuwerink from Ohio State University. Zuwerink used population and harvest data from 1990 through 1997.  The original exercise used mallard population and harvest data from 1961 to 1975. 

Because more life history information is known for mallards than any other duck species on the continent, the mallard was the only duck species considered by both derivation models.  Additionally, mallards are the most intensely banded species of waterfowl on the continent. 

In 2002, 20,651 total ducks (all species) were banded in Saskatchewan and 6,905 were banded in North Dakota.  Of those total bands, more than 52 percent were mallards in Saskatchewan and about 35 percent were mallards in North Dakota. 

Here’s a real-life example from Zuwerink’s analysis.  If you are a duck hunter from Arkansas, here are the top five source areas for the mallards your state harvests: 

1) Missouri River Valley (22.2 percent):  comprised of eastern North and South Dakota, western Minnesota, western Iowa and eastern Nebraska. 

2) Southeastern Saskatchewan (17.5 percent)

3) Southwestern Saskatchewan (16.6 percent)

4) Northern Saskatchewan, Northern Manitoba and Northern Ontario (15 percent)

5) High Plains (7.4 percent):  western North and South Dakota, western Nebraska, eastern Montana and Wyoming and far northeastern Colorado

For everyone else, we’ve posted mallard harvest derivation tables for each state and province.  Thanks to Dr. Bob Gates of Ohio State University for making these tables available.

Once you’ve mastered the concept of harvest derivation, it will give you a different perspective the next time you harvest a mallard.  While there are likely several areas that grow ducks for your state, you’ll be better equipped to decide where your precious dollars should go to give you and the hunters in your state the most benefit.