Common periwinkle
Littorina littorea
The steady small citizen of the north ledge. Counted in the Bream Frame every walk. A rise and fall of about 30% is ordinary; anything past that gets a second count.
Status: stable. Last fixed-frame count: 62.
On the rocks — Tidepool Watch
Green crab
Carcinus maenas
Non-native, abundant, unbothered by anything we do. We count them because the count itself is useful — an anchor against which other things can be measured. "Green crab weather" in volunteer-speak means "a normal day."
Status: abundant. Our count ranges 30–45 per quadrat.
Northern sea star
Asterias rubens
Not reliable anymore. Absent from most of our sites since the wasting years. We still check Spider Ledge's low pool at every walk. Finding one is a small private occasion.
Status: uncommon, watched. Last seen: 22 Aug, Spider Ledge.
Barnacles (line)
Semibalanus balanoides
We don't count barnacles; we measure the height of the barnacle line relative to the reference mark. A shift of a few centimeters over a decade is not nothing.
Status: present, line measured quarterly.
In the grass — Marsh Transects
Smooth cordgrass
Spartina alterniflora
The marsh's architecture. Height at each fixed station is measured to the centimeter. The inland edge, where spartina gives way to open water, is the single number we watch most closely.
Status: losing ground on lines 6, 7, 9. Stable on 3, 10. Gaining on none.
Atlantic marsh fiddler
Minuca pugnax
We count burrow entrances within the Pell-frame quadrat, not the crabs themselves (which are faster than any volunteer with a notebook). Burrow density is a coarse but consistent stand-in for population.
Status: dense on lines 1–4, thinning near the open-water edge.
Ribbed mussel
Geukensia demissa
Tucked at the base of spartina stems, doing slow, admirable work on water clarity. We log presence and approximate bed extent, not individuals — there are too many and they are stubbornly attached.
Status: present along most lines. Thinning where spartina has gone.
On the sandbars — Shorebird Log
Semipalmated plover
Charadrius semipalmatus
The dawn-shift regular. First arrival date has shifted four days earlier over the life of the log. A single dark breast-band; a run-and-stop gait that makes it easy to pick out of a mixed flock.
Status: annual. Arrival: typically early April.
Ruddy turnstone
Arenaria interpres
Fewer than there used to be. Count has about halved over nineteen years. Harlequin-patterned in breeding plumage; easier to identify in fall, when the pattern softens but the orange legs stay honest.
Status: declining locally. Peak fall count now 6–10.
Least sandpiper
Calidris minutilla
The smallest sandpiper on the bar, greenish-yellow legs if the light is right, often in mixed flocks with semipalmateds. Counts have held more or less steady — a small, quiet piece of good news.
Status: stable. Peak count: typically 40–60 in late July.
What's not here
Plenty. We don't log fish, beyond the occasional note of a juvenile under a rock. We don't track seals (our waters see harbor seals in winter; someone else watches them). We don't do insects. A species not on this page is not absent from the estuary; it is just absent from what our walks happen to measure.
If you keep your own notes on any of these and would like to compare, speak to Mei-Lin at an open-walk. We have made unexpected friendships that way.