It’s a good thing birders are able to identify species that they hear, but can't locate. Coastal birds whose home is in the salt marsh tend to be secretive; their songs and calls are heard more often than the birds show themselves among the dense Spartina stalks.
Photo of a marsh wren. "Cistothorus palustris CT" by Cephas - Own work. Licensed under CC BY-SA 3.0 via Wikimedia Commons -
The most common bird of tall creekside Spartina is the marsh wren, Cistothorus palustris. Like most wrens, they are shy and difficult to spot, but in spring and early summer the distinctive, melodious songs of the males fill the marsh (hear their song on the Cornell Lab of Ornithology website). Marsh wrens hunt spiders, grasshoppers, and other insects in the cordgrass. During breeding season, the male builds several flimsy nests among the Spartina leaves. When the female chooses a mate, she ignores his pitiful efforts and starts a final, well-constructed nest that the male dutifully helps finish. Egg laying must be timed to occur between the highest spring tides so that the young birds are hatched and fledged before the nest is flooded; submersion in saltwater would kill the nestlings.
Abandoned marsh wren nests are favored by a nocturnal marsh animal: rice rats. The rats often curl up in wren nests for daytime naps above the incoming tide. In a flagrant abuse of this hospitality, marsh wren eggs are a rice rat delicacy. In fact, predation by rats on wren nests may be a factor limiting the population size of these perky marsh birds.
Seaside sparrow perching, usually these birds are running around on the marsh surface.
Seaside sparrow (Ammodramus maritimus maritimus) Dominic Sherony licensed under the Creative Commons Attribution-Share Alike 2.0 Generic license.
Sharing the wren's habitat is the seaside sparrow, Ammodramus maritimus, a small olive-gray bird with a streaked breast and yellow stripe over the eye. The two species nicely divide the resources of the marsh. While the wren flits after insects and spiders in the cordgrass canopy, the sparrow seldom flies, but instead runs about on the marsh surface seeking small crabs, worms, and other benthic invertebrates. At first glance, the little bird scurrying through the Spartina stalks may be mistaken for a mouse. Herbert Kale, who wrote a monograph on the marsh wren in Georgia, commented: "I never collected a marsh wren with muddy feet, or a seaside sparrow with clean feet." The sparrows choose nesting sites in the short cordgrass stands of the upper marsh. A close relative of the seaside sparrow, the sharp-tail sparrow, Ammospiza caudacuta, breeds in northern salt marshes during summer and overwinters in southeastern salt marshes.
A clapper rail hunts in a marsh. Tijuana Slough NWR clapper rail uploaded by Dolovis. http://www.flickr.com/people/50838842@N06, Creative Commons Attribution 2.0 Generic license.
The larger clapper rail, Rallus longirostris, also known as a marsh hen, is a medium-size brown bird with a short tail and long bill. Abundant in Spartina stands, rails are not often seen, but their raucous call is a common sound.
I did see clapper rails in the marsh once or twice when we lived on Sapelo Island. One afternoon as I was watching our two little boys chase fiddler crabs at the edge of a large mudflat separating two stands of Spartina, I noticed a clapper rail nervously emerging from the cordgrass. The bird darted gingerly over the soft mud to the other patch of marsh. A minute later, another clapper rushed out of the Spartina and followed the first into the grass on the other side of the mudflat. Then the two rails repeated the performance, running back one after the other to the original Spartina marsh. Whether they were a courting couple or rivals, I never knew. They didn't come out again.
The preferred foods of clapper rails are squareback and fiddler crabs. They also feed on ribbed mussels poking up from the marsh mud, but not without a cost. Investigators have observed clapper rails that must have stuck a toe into a live mussel while trying to open the shell. The result was a rail stalking around with a mussel tightly clamped to a foot, or even with a missing toe..
Rails lay their eggs in the marsh grass, building woven nests in the tops of stalks that rise above all but the highest tides. Their eggs can survive an occasional inundation with saltwater. There is a fall hunting season for marsh hens. I was given a baked rail once. It looked like a naked pigeon and tasted gamey. I decided that I prefer my clapper rails running over mudflats between patches of cordgrass.