Photo: Bryan Stokes
Learn about the Saltmarsh Sparrow
Can you see why the bird shown above was once called a Sharp-tailed Sparrow? SALS were recently split from a close relative Nelson's Sparrow (Ammospiza nelsoni) into a new species, Saltmarsh Sparrow (Ammospiza caudacuta). We refer to the birds as "SALS" because that is the standardized banding code used to record data about birds seen or captured. It is the first three letters of the bird's first name, SALtmarsh, and the first letter of the second name, Sparrow.
The story begins with the Spring migration, with males arriving on the breeding grounds in early May in RI. Why do the males arrive earlier than the females? In many species, it is advantageous for males to find and defend the best territories and display colorful breeding plumage -all to get the attention of arriving females. However, SALS are the exception to the rule: there are no territories to defend and the plumages are identical for the both sexes.
This species is monomorphic, meaning that the males and females look identical in the field. Only upon close inspection during the breeding cycle can sex be determined.
By color-banding SALS, we can identify specific females and locate their nests. Using a grid pattern, we document which parts of the marsh are being utilized for nesting and other activities.
photo: Deirdre Robinson
Nest construction and egg stage (approximately 16 days)
Female SALS are among the hardest working birds on the planet, as they are the sole caretakers of vulnerable offspring. They form no pair-bonds with males, but rather are polygamous. It is common for every nest to have eggs fertilized by multiple males. Females construct nests in about 3-5 days, distributed in a non-random pattern in the marsh. They incubate 3-4 eggs for about 12 days.
Nests are ordinarily a simple cup. All nests are elevated above the ground substrate, and supported by stems along sides of nest, and sometimes by underlying semi-erect thatch. Structure is variable, sometimes thin and flimsy but usually moderately bulky. Some nests have a domed canopy, which helps keep eggs from flooding out of the nest at high tides. We are measuring the elevation of all the nests at Jacob's Point to determine the critical height above sea level that is required for survival of eggs and nestlings.
source: Cornell Lab. Of Ornithology - Birds of North America - Saltmarsh Sparrow breeding
photo: Deirdre Robinson
Interested in knowing more? Download our Developmental Guide to Aging Saltmarsh Sparrow Nestlings published in Rhode Island Naturalist.
Why is it helpful to determine the age of a SALS nestling?
The short answer is that it allows researchers to document the early development in the life history of this endangered species and correlate breeding success or failure with nestling age. Finding a nest with any combination of eggs and young allows us to retroactively determine when the nest was constructed and the first egg laid. This data informs us about potential changes in the breeding cycle over time as well as how the nesting cycle is impacted by flooding or depredation events.
Nestling Stage (approximately 10 days)
Two day old hatchlings are blind and devoid of feathers, except on their heads. When the female returns to the nest, the nestlings beg silently for food.
Rapid growth is necessary for nestlings to develop from naked hatchlings to fully-feathered young who are strong enough to climb out of the nest before the flooding tides occur, at least every 28 days of the lunar/tide cycle. There is very little margin for survival, given that these birds need about 26 days from nest construction until fledging. Increasingly, marshes are flooding before the peak high tides and at mid-cycles in the monthly lunar sequence, which dooms many nests to flooding.
Watch a short video (15 seconds) of a newly hatched Saltmarsh Sparrow in its nest!
video: Deirdre Robinson
photo: Deirdre Robinson
After being incubated for 12 days, and fed in the nest for about 10 days, the nestlings are ready to fledge before the next flooding tide. In the first nesting cycle of 2017, only 1 nestling was strong enough to leave the nest in time. After the RI state motto, we nicknamed her Hope. That is also the title of Emily Dickinson's famous poem that begins, "Hope is the thing with feathers..." Hope's story was written by Alex Kuffner and published in the Providence Journal on July 9, 2017.
Molt: changes in plumage with maturation.
Young birds must undergo a change primarily in body plumage (from low quality down to new, crisply defined feathers) to enable them to prepare for the rigors of Fall migration. By contrast, adult birds often show worn feathers due to their need to run through the saltmarsh grass, abrading their tail feathers as the hunt for food or return stealthily to their nests.
Juvenile plumage is a rich buffy color that is brightest on the eyebrow, malar stripe, and foreneck outlining the dusky ear coverts. Sides of neck, breast, and flanks are streaked with brown. Wing coverts and tertiaries broadly edged with yellowish buff, secondaries with russet, primaries and their coverts greenish, tinged olive gray, alula with white.
Eyebrow and malar stripe broad, sharply defined, and dull ochre, with malar stripe curving upward behind gray ear coverts, separated from eyebrow stripe by a narrow dark brown or blackish postauricular stripe. Molt limit between replaced formative tertials and more-worn juvenile secondaries identified Formative Plumage; the bolder buff-orange wing bar may also be indicative of this plumage.
The story of the breeding season ends here, as birds fly south at night (to avoid predators) to reach their wintering saltmarsh, somewhere between VA and FL. As fragile as life is during the breeding season, surviving the migrations poses additional hardships on these vulnerable birds.