Saturday, June 11, 2011

Day 27: Whatchu talkin bout, Willet?

NPS intern Sarah spent her first day in the marsh today. Upon arrival we found the willets chasing a heron around. Having driven off the heron, the willets turned their attention on us.

When they weren't dive bombing they were guarding my equipment.

Or house sitting for the ospreys, which haven't been seen since last week's encounter.

The water was low, and bottom of the main pool twitched conspicuously. I'd seen a crab in there before, and was afraid it might be the invasive green crab. But I was wrong. They were Callinectes sapidus, better known as the blue crab of jumbo lump fame. This photo shows how deftly it blends into the sediment of the marsh bottom.

As the tide rose they began their seaward migration through the sandy channels, where they were more easily photographed.

On the eastern edge of the mouth I found several horseshoe orgies. One male attaches to a much larger female, and is joined by other "satellite" males. The larger the female, the larger her following. She slips a few thousand eggs just under the sand near the high tide line. At that point the waiting males blast their sperm.

After conducting a series of paternity tests, University of Florida Biology Professor Jane Brockmann discovered that although satellite males aren't as close to the 'action' as an attached male, they often succeed in fertilizing eggs through strategic positioning.

Inside the marsh were dozens of ribbed mussels, Geukensia demissa, filter-feeding during the tidal shift.  The mussels of Rocky Point might present an interesting opportunity for research, since they appear to thrive despite week-long dry spells.

High of 87, average wind ESE @ 5 MPH, 5.8 high tide @ 03:42 PM. Moon 59% visible.
Water level recorded at 4 inch mark.
Birds seen in marsh: red winged blackbird, willet, green heron, great egret, common tern, least tern, oystercatcher, crow, skimmer
Birds seen in bay: black-bellied plover, ruddy turnstone, red-breasted merganser

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