A Flight of Passage!

A Flight of Passage!

By Jacob Vanderberg

It starts with a change. That first real bite of cold in early fall when the leaves have barely started to turn and daylight periods grow shorter. It isn’t a rapid change, but more of a coaxing that sends those first early migrants on their southward journey. Waterfowlers sense this as well and begin scanning the skies and wetlands with far more scrutiny than in previous months. This is an exciting time indeed because over the course of the next few months Mother Nature’s icy breath will open the flood gates sending millions of migrating waterfowl packing to their wintering locations.

One might simply assume that ducks and geese fly far enough south until the climate and food suits their needs. While this may be true in some cases, the trip is generally a lot more strategic and many species of waterfowl not only stop over in the same areas every year but they also breed and winter in the same areas. How do they find their way? Do weather patterns dictate where they go? There are many questions to answer so let’s take a closer look.

Migration is an adaptive strategy not only for waterfowl but for any species that endures it. The reason can be summed up in one word, “survival”. Waterfowl migrate to avoid harsh winter conditions and also to ready themselves physically for breeding and brood rearing. The exact time and rate at which waterfowl migrate is different from species to species and even the latitude they winter in may overlap a great deal yet still varies. Some species winter in tropical climates such as Mexico and South America. Some species winter as far north as Metro areas in Minnesota. Many species of waterfowl will remain as close to their breeding grounds as their bodies will permit.

What Starts Migration
Many of us think that weather has everything to do with the birds pushing south. This is very true but not solely the reason. The length of daylight also plays a big role in timing especially for early migrants such as Blue Wing Teal, Shovelers, Gadwall and some Pintails and Canvasbacks. Ducks can sense this and some species may decide to head south before the weather even starts to get colder. If you think about it, weather patterns are never the same from year to year but one constant that has remained relatively the same for thousands of years is the time when the sun rises and sets throughout the year.

Big weather events do however move a lot of birds when they happen. Species of waterfowl that are hardier such as Mallards, Geese, Swans, Mergansers, Divers, Black Ducks and Sea Ducks will hold out until the conditions force them to move. Why leave if you don’t have to right? The exact timing of any waterfowl migration is not clear but is likely related to photoperiod, the timing of reproductive events and molting.

How They Navigate Sight
All species of waterfowl have keen eyesight and this is a big tool for them when navigating across a continent. They use their eyesight in combination with memory to identify landmarks and landscape changes that aid in their trajectory. Think of when you may have traveled to a big city or new place and tried to navigate without the aid of modern technology. You do so based on the remembrance of specific landmarks and routes. When young waterfowl migrate for the first time they use the same imprinting abilities from identifying their mother to log memories of landmarks and key travel route identifiers.

Traveling at night is a little less advantageous as far as visual cues go but waterfowl still manage to use their eyesight to pinpoint directions. I once read an article about a migrating bird in the springtime that was placed into an astrodome. Upon release from any direction in the dome the bird would right its course to correlate with the position of the North Star. It is thought that waterfowl have the capability to do the same however no scientific evidence has proven this. Identifying major land features at night such as ridge lines, rivers, lakes and mountains is entirely plausible especially during full moon periods.

Magnetic Fields
Science has shown that the earth is encompassed by magnetic fields with two poles at the northern and southern most tips. It is thought that waterfowl have the ability to utilize this magnetic field to assess direction especially when using their homing abilities. Homing is a term that describes an animal’s ability to find a place of interest whether it be a birth place or home territory from any direction. Many species of ducks and geese rely on this homing ability to return to their place of birth or where they last reared a clutch of babies. Some ducks on the other hand such as teal rarely return to their natal origins. Either way it is fascinating to think about birds utilizing magnetic fields to navigate, and do so accurately!

One study I came across talked about placing small magnets on the heads of waterfowl during migration. This may sound cruel and I urge you not to try this but the birds in the study flew in the opposite direction they had been traveling. Coincidence? Maybe, but the facts are hard to neglect.

Small Climate Changes
Sometimes Mother Nature just likes to throw a wrench into the mix and bad weather strikes with little notice. The harsh weather events absolutely affect waterfowl and may scatter them about or funnel them into specific areas they had not intended on being. These events are what waterfowlers love to see in the forecast. A disruption to the normal migration trickle that in some cases can send millions of ducks and geese south in a matter of hours trying to get out of reach of the storm.

In contrast to this, hunters in the south sometimes see a reverse migration for the exact opposite reason. Unseasonably warm conditions or a brief warm front will allow waterfowl to exploit resources much further north in their wintering grounds than usual.

The complete itinerary for waterfowl migration is still largely a mystery. We can speculate based on observations and educated guesses but without hard scientific facts for each question all we can do is “speculate”. Some species migrate from one end of the continent to the other while others make small, more precise inland movements. One thing is for sure and that is when the migration is on waterfowl hunters are happy. It truly is amazing how our fowl friends make it through such arduous journeys and end up finding exactly where they want to go year after year.