Happy Mother’s Day!
I love you Mama! Thank you for your support and love and grits and eggs (over medium please) and for trying to point me in the right direction and still loving me when I took a wrong turn.
For Mother’s Day I’ve written about a particular mama of the marsh, the saltmarsh sparrow. The sparrows have have just arrived in Massachusetts from their southern wintering grounds. As June starts up so will their breeding and egg laying. Tidal marshes present particular challenges to a bird the lays it’s eggs on the ground. See how this hard-working mama bird does it in spite of tough conditions.
As she sits on her eggs under the canopy of soft grasses of the salt marsh, the tide nuzzles her nest. She shifts but doesn’t leave, the tide will not rise any more today.
But as the moon fills it will pull with the sun on the rope of the sea against the earth in a Newtonian tug-of-war and bring the spring tides on top of the marsh. When tides flood she will have to abandon the nest and wait for the ebb. Then she will return to incubate her eggs if they remain.
In the past she has returned to nests emptied of its eggs by the tide or filled with limp, drowned chicks. The sun and moon don’t know about the gumball sized, chalky off-white eggs or the raggedly bald and screaming pink fledglings of the saltmarsh sparrow that sometimes nestled in the grass. The only follow their astronomical rhythms.
In her age, she has learned these rhythms. She now lays her eggs 2-3 days just after the highest spring tides (often the full-moon tides). The next marsh-overtopping waters arrive 10 days later. A saltwater baptism as eggs is how many saltmarsh sparrow offspring join this world. She has learned that a nest with a domed-canopy will catch floating eggs and keep them in the nest as opposed to an open-canopy nest. Once the last overtopping tide ebbs, the chicks hatch. She now spends her days catching prey – grasshoppers, spiders, small crustaceans and flies – for her incessantly mouth agape and helpless and vulture-skinned young. It is only she that rears the young, the males of her species are promiscuous and take no part in child-rearing. She faces the tides alone. And since she has learned their rhythms and she knows that she must fledge her young before the tides return in the next 10 days.
Despite what she has learned, 3 out of every 5 of her nests fail. This is typical for her species. After each failed nest, she starts again. Make a nest, find a mate, breed, lay eggs, incubate and wait. The summer is short and offers only three chances.
Her most successful brood was a re-nest that was in a part of the marsh that was 2 ½ inches higher than the old nest. The new nest never flooded. The distance between success and failure being only half her body length.
At 10 years old, she is old by sparrow standards and this is her last brood. She has made her last trek from her overwintering grounds as far away as Florida to her natal breeding grounds of the Great Marsh in Massachusetts. She comes here because there are fewer predators than down south and the Great Marsh has acres heaped upon acres of high-marsh habitat of soft grasses, which only exist in bands down south. These grasses seclude her. She is a secretive bird, brown and small, well-suited for hiding in the marsh grasses. She is modest, allowing herself only the slightest blush of orange or yellow on her cheeks, swept across her face as though she flew quickly against an artist’s brush. Hunkered in tufts of grass, she is heard more often than seen, a sound like the high-pitched squelch of a white-hot iron rod plunged into water.
She has returned one last time to the Great Marsh because her role as a mother is not yet done.
Saltmarsh sparrow (Ammodramus caudacutus) eggs, Ipswich, Massachusetts
All About Birds – Cornell Lab of Ornithology
Gjerdrum, C., K.Sullivan-Wiley, E. King, M. Rubega, A.S. Elphick. 2008. Egg and chick fates during tidal flooding of saltmarsh sharp-talied sparrow nests. The Condor 110: 579
Greenlaw, J. and G.E. Woolfenden. 2007. Wintering distributions and migration of saltmarsh and Nelson’s sharp-tailed sparrows. The Wilson Journal of Ornithology 119:361
Humphreys, S., C.S. Elphick, C. Gjerdrum and M. Rubega. 2007. Testing the function of domed nests of saltmarsh sharp-tailed sparrows. Journal of Ornithology of Field Ornithology 78:152.