Posts Tagged 'crabs'

YCNH

Yellow-crowned Night-herons, Nyctanassa violacea, at the Salt Marsh Nature Center.“Where the yellow-crown’d heron comes to the edge of the marsh at night and feeds upon small crabs” wrote Whitman in Song of Myself. The low tide here reveals fiddler crabs amongst the marsh grasses. This one grabbed a crab with some nearby seaweed, took the dual mouthful to the water, and shook the crab and seaweed apart. The crab went plop in the shallows, but was instantly fished up and tossed into the mouth.Right down the gullet. Sure got dark early for that crab.

Of course, these birds will also eat whatever they can catch, from worms to small mammals. A Black-crowned Night-heron (Nycticorax nycticorax) also seen here recently was chased by a relay of Red-winged Blackbirds as it flew over the marsh. The blackbirds were protecting their territory and nests from another lusty predator — which we’ll catch up with tomorrow.It’s usually difficult to see the yellow in the crown on a bright day. The violet on the back, which is the source of the specific epithet violacae, however, is sort of visible here. A gray violet…

Sand Crab

Emerita talpoidaThe Atlantic Sand Crab (Emerita talpoida) is also known as the mole crab and the sand flea (confusingly, since there are, in fact, amphipod sand fleas).Emerita talpoidaThese streamlined animals are, at any rate, crustaceans. As Sarah Oktay explains from the place I first came across them, they are surf-zone specialists, and pretty important in that harsh habitat. Emerita talpoida

Hermits

Ilyanassa obsoletaI believe these are Eastern Mud Snails (Ilyanassa obsoleta), which look like rocks until you look closer. There are quite a few of them in Jamaica Bay. And some of them were moving much too quickly. They were, in fact, hermit crabs, who use found snail shells for their own.hermit3Hermits don’t have protective shells like your usual crab species; they use snail shells instead, swapping to larger ones as they grow.hermit2This article argues that hermit crabs populations are going quite well because of a surplus of shells to choose from, from the introduced Common Periwinkle (Littorina littorea) which has spread up and down the East Coast. (Periwinkles generally like rocky shores, so the New York estuary doesn’t seem to have many of them.)Hermit1I don’t know the species here. Anybody?

Hermit crabs from the Caribbean, rather larger than these, are exploited by the aquarium trade, and as a result, the internet is full of wails of children of all ages bemoaning their dead and dying “pets.” As animals wrenched from their own habitats (these are usually land crabs like the “Purple Pincher”), they potentially threaten local species and other crustaceans with diseases.

Variations on Legs

fiddlerFiddler crabs in the tiny patch of ever-so-green right now salt marsh at Pier One. On the jumbly rocks next to it, a number of these spiders:spiderI have returned from a two week trip abroad. I have a new computer. I am ready to blog again.robinA young New World Robin, SO different from the Old World ones, as pictured yesterday.

Dead Horse Bay

Yellow-rumped warblers and Green Darner dragonflies before we got to the landfill edge.One of two Royal Terns, Thalasseus maximus, both with bands on their left legs. Not a commonly sighted bird in the city; I didn’t know what they were at first. The smaller Common and Little Terns we see here during summer have already gone south. These Royals sound quite different from our regular terns, and one of them was excreting a lot. I later read that they defecate around the sides of their scrapes (nests) to build up a a hard rim of guano, possibly as a defense against minor flooding on the low-lying islands they breed on.The Asian or Japanese Shore Crab, Hemigrapsus sanguineus. Found about a dozen washed up on the beach perpendicular to the Gil Hodges Bridge. Three spines on each side of the carapace, red spotted claws, dark bands on the legs are your field marks for this invasive. Not good news for already fraught Jamacia Bay (Dead Horse being a nook on the north side of Jamaica Bay, if you haven’t wandered its singing glass beach.)

We’ve Got Crabs

The triangle of saltmarsh ot the southern end of Pier One at Brooklyn Bridge Park is an experiment. It’s cordgrass (Spartina alterniflora), which thrives even though it’s flooded by salt water at high tides. In flower now, it will send many seeds off on the currents, searching for mudflats. Key to its success, though, is the matrix of roots in the mud. Two other keys are ribbed mussels and fiddler crabs; together the three species anchor an incredibly productive and important ecosystem, nursery for many fish species and acting as kidneys by cleaning water.

Now, neither the mussels nor the crabs were “planted” with the cordgrass when this went in two years ago. That’s what I mean by experiment. But the fiddler crabs (Unca pugnax, I think) have found the marsh. Could there be mussels in there as well? This is a male; I also saw one female. Females lack the big bull-fiddle claw, which the males used to show off and protect their tunnels. Now I only saw two individuals, and places like Four Sparrow and Pelham bay are absolutely scurrying with them (these two observed at high tide, mind you), but everybody starts small. UPDATE: returning four days later at lower tide, I saw several more and their tunnels; they sense your vibrations as you approach and hide just before you get a good look at them, so try sitting on the rocks and waiting until they emerge again.Just a few feet away, I found evidence of a second species of native crab, the Blue or Blue Claw (Callinectes sapidus). The Hudson has a robust population of this species, according to this. This was a young one, 1.75″ long. Being delicious, it has been scarfed up by something; those are additional bits of chitinous remains above the overturned carapace. Those points on the sides of the carapace are tell-tale for this species.

[Crab and crab shell were photographed in the water. Image may thus appear larger than is actually the case.]

Sheepshead Bay

Ten piers, ten local creatures of the sea.


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