The low water of March is the time to see freshly exposed mud spotted with dabbling pits. Why mud? Why dabbling pits?
Turn back the calendar to the normal water level of the previous summer. Waves wash the sandy beaches of the West Arm. The breaking waves pick up sand of all sizes and first wash it a short distance up the beach. The water then flows back down the slope but now carries the sand grains and silt out into the Lake.
However, not all particles are treated equally: as the velocity decreases as water flows back into the Lake, the larger grains of sand settle out adjacent to the shore, while the silt is carried a bit farther offshore. The process is repeated with every wave.
The particles that had been picked up by the waves have been sorted, with the bigger ones near the water’s edge and the smaller ones farther out. The offshore silt results in the mud that is a staple of beaches along the West Arm.
The mud becomes a home for a rich range of tasty biota. Dabbling ducks, geese, and swans love to feed there. They tip their butts in the air and extend their necks downward as their bills make circular sweeps in the mud in search of delectables. They dabble in the mud.
It is the dabbling pits that water fowl make in mud that are exposed when the Lake level drops.
The Canada Goose is one of many dabbling water birds to tip up and sweep the mud below.
Low water exposes the dabbling pits made earlier by water fowl in what had been offshore mud.
As a geologist I am familiar with what are referred to as ‘sedimentary structures’, which are features visible in sediments and sedimentary rocks of all ages. Most are the result of physical processes such as the interplay of currents and sorting as you describe. But some, such as tracks and burrows, owe their origin to the action of organisms. Alistair, your dabbling pits are a new one for me!
Carlo, I can think of two reasons for the lack of such an observation at the Coast: tidal motion erases the evidence; you are bereft of geese.
You keep informing with your observations…I’ll recognize dabbling pits from now on!!! Thanks.
Not sure when I’ll get the opportunity to impress (or annoy) someone with this knowledge but it’s good to know how those depressions in the mud were made. I never would have thought of them in geological terms either! I suppose Floridians could see these on a daily basis as the tides change where Roseate Spoonbills and others of their ilk feed?
Well! you learn something new every day. I often wondered how those depressions in the mud were made
How very interesting. Thanks again