The Direction Ducks Land

My thanks to my fellow Fellows at the Royal Institute of Navigation for drawing my attention to some research that slipped past me a few years ago.

Hynek Burda, of the Czech University of Life Sciences in Prague, led a team of 11 zoologists in a study of the way birds land on water. They documented the landings of nearly 15,000 birds of 14 species belonging to 3,338 flocks spread across 8 countries over the course of a year.

The results were in some ways predictable and in one way remarkable.

The predictable part is wind direction. All birds, all aircraft, all flying things have to take wind direction into account when landing. The reason for this can be demonstrated with a simple thought experiment.

Imagine a bird lands whilst flying at 10 mph on a day when the wind is also blowing at 10 mph. If that bird lands in the same direction as the wind is blowing then its feet have to touch the ground at 20 mph - very uncomfortable, possibly unsafe and certainly inelegant. The best possible result will be a rolling, flustered bird. However if the same bird lands into wind, then it can place its feet down on ground that it is not moving over. A safe and suave way to touch ground.

If wind has long been known to be the deciding factor on days when it blows, the team of zoologists wanted to know what factors influence the direction of landing on windless days. This is interesting for a number of reasons, not least because it can illuminate how animals in large flocks avoid collisions which can be beneficial in lots of other fields too. Their thorough study found that waterfowl will land in line with the earth's magnetic field, they align north-south on approach.

"The effect of the time of the year, time of the day (and thus sun position), weather (sunny versus overcast), light breeze, locality, latitude, and magnetic declination in 2,431 flocks of mallards (Anas platyrhynchos) and found no systematic effect of these factors upon the preferred direction of landing. We found that magnetic North was a better predictor for landing direction than geographic North."

Their research paper can be found in the journal Frontiers in Zoology.

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