The most interesting observation I received this week was an email and series of photographs from the Chesapeake Bay area of Virginia. While photographing marsh birds, Martin Mikulas managed to get a series of shots of a river otter hunting at low tide for one of its favorite prey, blue crabs.As the series of photos reveals, the otter completely ignores the hundreds of fiddler crabs within easy reach on either side of the trough it moves through. Once it reaches a small but deep pool, it begins diving, surfacing six times with a large blue crab in its mouth each time over the 30 minutes it was observed.
Luanne Johnson, a river otter researcher stationed on Martha’s Vineyard, reports that otters feast on blue crabs inhabiting the island’s salt ponds. In its freshwater haunts, crayfish are one of its favorite foods. It has been known to travel long overland distances to reach freshwater ponds containing an abundance of this freshwater crustacean.
We wondered why otters avoid the much more abundant and easily caught fiddler crabs that inhabit most of the intertidal edge of our bays and harbors. I agree with Luanne: Fiddlers probably have a ratio of nutritious meat to indigestible shell that just doesn’t work for the otter.
While paddling along the edge of salt marshes, whether it be an area of peaty substrate pockmarked with small burrows, home to the mud fiddler (Uca pugnax), or along the edge of young, poorly developed salt marsh containing cordgrass (Spartina alterniflora) growing in beach sand, home to the sand fiddler (Uca pugilator), it is not unusual to come across huge numbers of these crabs moving across the intertidal zone at low tide, completely exposed and in plain sight. And easily rounded up and caught.
Where, I’ve often wondered, are the crab predators, and why aren’t they taking advantage of this bounty?
There is no shortage of predators of the fiddler crab. Among the list are raccoons, willets, gulls, crows, herons and egrets, all common here on Long Island. And that’s just the land dwellers; there’s a substantial list of aquatic predators (including the voracious blue crab). Yet I’ve never witnessed any zero in on the mass of easily caught crabs. Not even an individual of any of the three species of ubiquitous gulls found here.
I see this fiddler crab herding phenomenon a half dozen times a summer, and recently learned that scientists have a name for it: droving. Still, I have yet to find an explanation for this seemingly dangerous behavior.
Along the ocean beach tideline, and noticeable when swimming and paddling beyond the surf zone, are jelly bean-sized clear organisms. These are a type of tunicate called salp that form fragile chains several feet long that are easily broken into their much smaller components as they get tossed about by surf and rough water.
For many years, I’ve referred to this time of the year—most of September, when the days are warm, dry and sunny, and the nights are cool—as “Indian summer.” It’s a short season that is perfect for all sorts of outdoor activities: sailing (there’s usually a nice, steady and reliable breeze, unlike the wind in summer), swimming (the water is still warm and clearer than summer), surfing (waves pick up), hiking (perfect temps for a walk, and pesky insects disappear) and biking (as with hiking, warm but not hot, and less traffic).
Jim Nicoletti recently informed me that I was wrong. According to the Farmer’s Almanac, Indian summer is not a cool, dry spell that follows hot, humid weather, but a warm spell that follows cold weather or a hard frost. That pushes Indian summer much later in the fall, into late October and early November.
I’ll have to come up with another name for this incredible warm, but not too warm, dry and sunny weather we’ve been having recently. We’ve also been treated to some pretty fun surf, in clear, 70-plus-degree water. Can’t beat that.
However, most of September has been more like summer in terms of weather, with 12 of the month’s 26 days recording temperatures over 80 degrees and one hitting the 90s. So far, we’re 4 degrees above the average temperature for September, and we’re continuing the below-average rainfall trend from spring.
The tupelo trees in the large freshwater swamp along Bendigo Road in Amagansett have turned a brownish-maroon color this year, unlike the more typical showy and vibrant scarlet red they often display. This is our first major tree to show signs of the coming fall foliage, and its lackluster display may be the result of the low precipitation during this year’s growing season.
On the other hand, the tupelos, as well as the flowering dogwoods, have produced what seems to be a bumper crop of fruit. Both are high on the list of nutritious foods eagerly sought by birds that are forced to shift at this time of year from high-protein insect diets to one that includes more plant-based foods.
Flocks of birds have been feeding on both. American robins, tufted titmice, and gray catbirds have hit the trees in my yard this week. Eric Salzman observed those plus red-bellied woodpeckers, flickers, blue jays, crows, gold finches and house finches gulping the tupelo fruits.