Duck Migration Article

Migration

WAITING FOR ‘NORTHERN DUCKS’
By Norman Seymour

Waiting for “northern ducks” is a fact of life for nearly all duck hunters. In times past the ducks usually showed up, more in some years than others. A cold autumn blow held the promise of new birds. This was true even during the 1980s when prairie-duck populations fell to historic lows.

After water returned to the prairie in the mid-1990s, and duck numbers increased, hunters had a couple of good years. The U.S. Fish and Wildlife Service at one point claimed the autumn migration was the biggest since the 1950s – a flight of 100 million ducks.

But the euphoria was short lived. Despite optimistic forecasts, hunters soon began asking, “Where are the ducks?” A few waterfowlers reported an abundance of ducks and reasonably good shooting, but this was not widespread. Many hunters combed the continent looking for tens of millions of ducks that, if fall-flight estimates were correct, were out there somewhere.

Where were they? I don’t believe they existed. Many veteran hunters share my view. They consider the fall flight forecasts grossly optimistic.

Waterfowl tend to migrate along traditional corridors or flyways as they move between their breeding and wintering grounds. This is predominantly a north/south movement, but for some species there also is a west/east component. The key to understanding the timing and distribution of ducks along these routes is the availability of food. Just like daily movements of ducks can be traced to feeding behavior, changes in migration are linked to availability of food. Knowing their feeding habits is the key to understanding where ducks are likely to be, and when they’re likely to be there.

Most duck species generally show up at specific locations along the migration corridors within a predictable window of time. The so-called “calendar migrants” are most faithful to a schedule. Blue-winged teal, shovelers, gadwall and wood ducks, along with some divers, usually show up at the same location each year within a brief time span. Their migrations reflect changes within their bodies that are probably triggered by changes in length of daylight, something that is constant and hence predictable from year to year. But food availability is the critical element. By early September the feeding opportunities of blue-wings are becoming restricted on their northern breeding grounds. Consequently, they leave before weather deteriorates. In general, the species of ducks that require specialized foods, or display rigid feeding behavior, are more predictable in the timing and routes of migration.

The arrival of mallards and black ducks along migration corridors is much less predictable. Their expected arrival is a perennial hot topic among hunters. Their un predictability reflects the fact these ducks are generalists. They feed opportunistically on a variety of natural and agricultural foods. Grain crops have been a boon for these ducks. Changes in agricultural practices, coupled with the construction of large impoundments and warm autumns, have profoundly influenced the timing of their migrations. A classic example involves the late Van Campen Heilner, who hunted along the Illinois River in the 1920s and 1930s. He wrote that “the twenties of October, like the ides of March, mark the full tide of the mallard migration” from Peoria to Cairo, Ill. Today’s peak migrations do not occur until November.

Cold temperatures are rarely a problem for these large-bodied ducks. They can go for several days without feeding, relying on their body reserves for energy and warmth. In Nova Scotia, where I live and conduct my research, several thousand black ducks spend the winter on tidal estuaries despite stormy weather and long periods of sub-zero temperatures. They feed on a diet of plant and animal matter that they wouldn’t consider except under extreme conditions. Not only do they survive, they remain in good condition. They are successful breeders when spring arrives.

But these estuary ducks are exceptions. Freezing temperatures that put a layer of ice on wetlands, when coupled with snow that covers stubblefields, provide the impetus to make most inland waterfowl leave an area. Some 5,000 greater snow geese and about 500 mallards and black ducks used the same grain fields that I hunted last autumn in southeastern Ontario. They departed two days after the arrival of snow that prevented the birds from finding food. This is the usual response of waterfowl.

A delayed migration is fundamentally different from short-stopping. We have known for decades that Canada geese can be “short-stopped” north of their traditional wintering grounds by providing them with food and roosting water. The most notable example of post World War II duck short-stopping occurred along the Columbia River in Washington and Oregon where changing agricultural practices and a hospitable climate resulted in the over-wintering of myriads of mallards that once winged south to California.

This is probably happening with some mid-continent mallards, but the new gatherings hunters talk about today are too small to account for millions of missing ducks. An exception might involve the large build-up of mallards in southern Missouri where increasing acreages of rice attract and hold great numbers southbound mallards. But this amounts to a slight northward shift rather than a geographically significant change that reflects the historical definition of “short-stopping.”

Some who have in recent years experienced the worst mallard hunting in memory argue the ducks must have changed migration routes, but it is doubtful that millions of mallards fled to another flyway. Major changes in migration patterns are usually much more gradual.

Diving ducks such as canvasbacks, redheads and bluebills tend to leave the breeding grounds around the same time each year. The timing of their departure from northern staging areas may depend on local factors like hunting disturbance and weather, but availability of food is always crucial to how long these specialized feeders stay anywhere. Depletion of food causes them to leave an area.

The diets of ducks can change to some extent. Scaup migrating along the Great Lakes/St. Lawrence River system now feed on zebra mussels. These accidentally introduced, exotic shellfish have changed the distribution of some scaup, but most still feed on traditional foods in traditional locations. If the traditional species haven’t arrived within a couple of weeks of when they’re expected, anxious hunters have every reason to be concerned.

Hunters sometimes confuse late-season concentrations with a delayed migration. This was evident on an early November bluebill hunt I made on the Delta marsh in the 1960s. There were only a few patches of open water. Perhaps 8,000-10,000 birds concentrated on these small patches. It was dramatic to see so many ducks on these small areas, but the late-migrating scaup were only a tiny fraction of the bluebills that earlier migrated southward. We enjoyed wonderful shooting, but the birds were gone the next day, probably making some Minnesota hunters very happy. Late migrants are never more than a small component of diving-duck populations.

Southern hunters eager for the arrival of new ducks often complain about unseasonably warm weather holding ducks “up north.” While this may be true, northern autumns invariably witness periods of cold that bring ice and snow. A few birds may wait out these cold snaps in anticipation of milder weather, but most take this as their cue to depart. Two or three days of freezing temperatures prompt ducks to move, including mallards. Southern hunters who wait for ducks long after the northern prairies have experienced several winter blasts may already have seen a majority of birds that are coming their way.

Thus, it is hard to avoid the conclusion that the U.S. Fish and Wildlife Service in recent years grossly over-estimated the autumn migration. After a season as poor as the one just experienced, it’s difficult to conclude great numbers of ducks are out there somewhere, especially if you consider there are millions of “missing” ducks.

Migration

WAITING FOR ‘NORTHERN DUCKS’
By Norman Seymour

Waiting for “northern ducks” is a fact of life for nearly all duck hunters. In times past the ducks usually showed up, more in some years than others. A cold autumn blow held the promise of new birds. This was true even during the 1980s when prairie-duck populations fell to historic lows.

After water returned to the prairie in the mid-1990s, and duck numbers increased, hunters had a couple of good years. The U.S. Fish and Wildlife Service at one point claimed the autumn migration was the biggest since the 1950s – a flight of 100 million ducks.

But the euphoria was short lived. Despite optimistic forecasts, hunters soon began asking, “Where are the ducks?” A few waterfowlers reported an abundance of ducks and reasonably good shooting, but this was not widespread. Many hunters combed the continent looking for tens of millions of ducks that, if fall-flight estimates were correct, were out there somewhere.

Where were they? I don’t believe they existed. Many veteran hunters share my view. They consider the fall flight forecasts grossly optimistic.

Waterfowl tend to migrate along traditional corridors or flyways as they move between their breeding and wintering grounds. This is predominantly a north/south movement, but for some species there also is a west/east component. The key to understanding the timing and distribution of ducks along these routes is the availability of food. Just like daily movements of ducks can be traced to feeding behavior, changes in migration are linked to availability of food. Knowing their feeding habits is the key to understanding where ducks are likely to be, and when they’re likely to be there.

Most duck species generally show up at specific locations along the migration corridors within a predictable window of time. The so-called “calendar migrants” are most faithful to a schedule. Blue-winged teal, shovelers, gadwall and wood ducks, along with some divers, usually show up at the same location each year within a brief time span. Their migrations reflect changes within their bodies that are probably triggered by changes in length of daylight, something that is constant and hence predictable from year to year. But food availability is the critical element. By early September the feeding opportunities of blue-wings are becoming restricted on their northern breeding grounds. Consequently, they leave before weather deteriorates. In general, the species of ducks that require specialized foods, or display rigid feeding behavior, are more predictable in the timing and routes of migration.

The arrival of mallards and black ducks along migration corridors is much less predictable. Their expected arrival is a perennial hot topic among hunters. Their un predictability reflects the fact these ducks are generalists. They feed opportunistically on a variety of natural and agricultural foods. Grain crops have been a boon for these ducks. Changes in agricultural practices, coupled with the construction of large impoundments and warm autumns, have profoundly influenced the timing of their migrations. A classic example involves the late Van Campen Heilner, who hunted along the Illinois River in the 1920s and 1930s. He wrote that “the twenties of October, like the ides of March, mark the full tide of the mallard migration” from Peoria to Cairo, Ill. Today’s peak migrations do not occur until November.

Cold temperatures are rarely a problem for these large-bodied ducks. They can go for several days without feeding, relying on their body reserves for energy and warmth. In Nova Scotia, where I live and conduct my research, several thousand black ducks spend the winter on tidal estuaries despite stormy weather and long periods of sub-zero temperatures. They feed on a diet of plant and animal matter that they wouldn’t consider except under extreme conditions. Not only do they survive, they remain in good condition. They are successful breeders when spring arrives.

But these estuary ducks are exceptions. Freezing temperatures that put a layer of ice on wetlands, when coupled with snow that covers stubblefields, provide the impetus to make most inland waterfowl leave an area. Some 5,000 greater snow geese and about 500 mallards and black ducks used the same grain fields that I hunted last autumn in southeastern Ontario. They departed two days after the arrival of snow that prevented the birds from finding food. This is the usual response of waterfowl.

A delayed migration is fundamentally different from short-stopping. We have known for decades that Canada geese can be “short-stopped” north of their traditional wintering grounds by providing them with food and roosting water. The most notable example of post World War II duck short-stopping occurred along the Columbia River in Washington and Oregon where changing agricultural practices and a hospitable climate resulted in the over-wintering of myriads of mallards that once winged south to California.

This is probably happening with some mid-continent mallards, but the new gatherings hunters talk about today are too small to account for millions of missing ducks. An exception might involve the large build-up of mallards in southern Missouri where increasing acreages of rice attract and hold great numbers southbound mallards. But this amounts to a slight northward shift rather than a geographically significant change that reflects the historical definition of “short-stopping.”

Some who have in recent years experienced the worst mallard hunting in memory argue the ducks must have changed migration routes, but it is doubtful that millions of mallards fled to another flyway. Major changes in migration patterns are usually much more gradual.

Diving ducks such as canvasbacks, redheads and bluebills tend to leave the breeding grounds around the same time each year. The timing of their departure from northern staging areas may depend on local factors like hunting disturbance and weather, but availability of food is always crucial to how long these specialized feeders stay anywhere. Depletion of food causes them to leave an area.

The diets of ducks can change to some extent. Scaup migrating along the Great Lakes/St. Lawrence River system now feed on zebra mussels. These accidentally introduced, exotic shellfish have changed the distribution of some scaup, but most still feed on traditional foods in traditional locations. If the traditional species haven’t arrived within a couple of weeks of when they’re expected, anxious hunters have every reason to be concerned.

Hunters sometimes confuse late-season concentrations with a delayed migration. This was evident on an early November bluebill hunt I made on the Delta marsh in the 1960s. There were only a few patches of open water. Perhaps 8,000-10,000 birds concentrated on these small patches. It was dramatic to see so many ducks on these small areas, but the late-migrating scaup were only a tiny fraction of the bluebills that earlier migrated southward. We enjoyed wonderful shooting, but the birds were gone the next day, probably making some Minnesota hunters very happy. Late migrants are never more than a small component of diving-duck populations.

Southern hunters eager for the arrival of new ducks often complain about unseasonably warm weather holding ducks “up north.” While this may be true, northern autumns invariably witness periods of cold that bring ice and snow. A few birds may wait out these cold snaps in anticipation of milder weather, but most take this as their cue to depart. Two or three days of freezing temperatures prompt ducks to move, including mallards. Southern hunters who wait for ducks long after the northern prairies have experienced several winter blasts may already have seen a majority of birds that are coming their way.

Thus, it is hard to avoid the conclusion that the U.S. Fish and Wildlife Service in recent years grossly over-estimated the autumn migration. After a season as poor as the one just experienced, it’s difficult to conclude great numbers of ducks are out there somewhere, especially if you consider there are millions of “missing” ducks.