Saturday, August 23, 2008

Terminal velocity of mussels

Yesterday Leslie and I paddled along the edge of Cape May Harbor, again showing our prowess with tide charts by struggling against the ebbing tide on the flip side of our voyage.

Because pushing against the tide is tiring, I edged towards the beach and just drifted for a minute.

While doing pretty much nothing, I noticed a gull dropping something.

It followed the object, picked it up, the swooped back up, higher and higher, hovered a moment, then dropped the object again.

Gulls are marvelous fliers, despite the inane way they're pictured in Jonathan Livingston Seagull--I once saw a flock of them chasing down insects, rivaling swallows in their gyrations.

After its fourth try, this time successfully nailing a small bed of rocks on the beach, the gull had its meal.

Now, I know this has been reported, and I have found smashed shells on jetties, presumably from gulls, but I had never seen it done.

A few things struck me:
  • The gull did not randomly drop the mussel--he clearly was aiming for the small pile of rocks.
  • As the gull hovered upward, he went a bit higher than gulls usually do when just hanging around--it knew enough to get some air between its meal and the rocks below
  • The gull consistently went to about the same height, and it took a bit of effort to get there.
So here are my bizarre questions of the day, which should be answerable, though I have about 37 other things I should be doing.

How far does it take a falling mussel to reach terminal velocity at sea level?
How close was that gull to that height?

I bet that gull was about as close to the answer through experience as I'm likely to calculate.

(Herring gull photo by Adrian Pingstone, 2003, via Wikipedia Commons; mussel photo by Joan Muller, Waquoot Bay National Estuarine Research Reserve, 1996, via NOAA)

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