• by Dr. Sarah D. Oktay, Managing Director UMass Boston Nantucket Field Station •
We are blessed to have the 17 acre Folger’s marsh as the centerpiece of the Nantucket Field Station. It is populated by an enormous menagerie of egrets, herons, and cormorants among other marsh birds. I usually don’t write about our magnificent avian friends because so many excellent bird experts write about them. Edith and Ginger Andrews, Ken Blackshaw, and Vern Laux provide our island with accurate and entertaining commentary in the paper and in books they release. But I would be remiss to not share some information about our marshy denizens and many people who visit the field station don’t know about these graceful fish stalkers. So here is a little bit of marsh bird 101.
What are the white birds slowly stalking about on thin little legs? Well they are Snowy and Great egrets. You can tell them apart by height and leg and bill colors. The very large ones are the Great Egrets or Ardea alba egretta (“Ardea” is New Latin from the Latin for heron, derived from the Greek word for “erōdios” for “heron “) also known as common egret, large egret or great white heron. The etymology of the word “egret” goes through a long and winding path, but it always ends at the same point; The word starts from Middle English, travels through Anglo-Norman egret, Old French aigrette (“egret”), from Old “Provençal aigreta”, diminutive of “aigron” (“heron”), from Frankish “haigro (“heron”) and is cognate (has the same linguistic derivation) with Old High German heigaro (“heron”), Old English “hrāgra” (“heron”). The Great Egret, unlike the other egrets, does not belong to the genus Egretta but together with the great herons is today placed in Ardea. Got it? Good! Heron tends to be a catch-all phrase for these birds and people often confuse them with cranes.
The Great Egret is a large heron with all-white plumage. Standing up to 1 m (3.3 ft) tall, this species can measure 80 to 104 cm (31 to 41 in) in length and have a wingspan of 131 to 170 cm (52 to 67 in). Body mass can range from 700 to 1,500 g (1.5 to 3.3 lb), with an average of around 1,000 g (2.2 lb). It is thus only slightly smaller than the Great Blue or Grey Heron (A. cinerea). Apart from size, the Great Egret can be distinguished from other white egrets by its yellow bill and black legs and feet, though the bill may become darker and the lower legs lighter in the breeding season. Great egrets prefer large marshes with less perimeter and more central areas with big patches of Spartina alterniflora (salt marsh cordgrass ) and large salt pannes (those little pond areas that support juvenile fish) for easy pickings (from Mass Audubon article at end of text).
The other very common marsh occupant who also loves big marshes (and cannot lie) with lots of salt pannes and lots of S. alterniflora is the snowy egret (Egretta thula). Snowy egrets are magnificent birds with very white plumage, black legs, and yellow feet (from http://www.allaboutbirds.org/guide/snowy_egret/id accessed August 31st, 2013). I have included two excellent photos by my husband Len Germinara who has taken literally hundreds of pictures of Great and snowy egrets.
Other marsh birds you will likely see include Great Blue Herons, Black Crowned Night Herons (my favorite) and an assortment of cormorants, whimbrels, a type of curlew (Numenius phaeopus), and Willets, a type of sandpiper (Tringa semipalmata) which displays a striking black and white stripe on each wing in flight and also has a pretty harsh call (http://www.allaboutbirds.org/guide/Willet/id). Lesser yellow legs (Tringa flavipes) another sandpiper type shorebird can often be seen sharing the mudflats. These medium-sized shorebirds are active feeders seen running around and chasing fish. They have a brown, gray, black and white mottled coloring with long, bright yellow legs, a long neck and thin long bill with a white rump and belly. You will also see various ducks gulls and cormorants (Double Crested and Great) preening and drying their wings on our mud flats or paddling around the salt marsh inlets and channels. Once in a great while you may see an ibis or bittern.
The Black Crowned Night Heron (Nycticorax nycticorax) is the most common heron found throughout the world, inhabiting at least five continents. Adults are approximately 64 cm (25 in) long and weigh 800 g (28 oz). They have a black crown and back with the remainder of the body white or grey, red eyes, and short yellow legs. They have pale grey wings and white under parts. Two or three long white plumes, erected in greeting and courtship displays, extend from the back of the head. The sexes are similar in appearance although the males are slightly larger. Black-crowned Night Herons do not fit the typical body form of the heron family. They are relatively stocky (they prefer big boned) with shorter bills, legs, and necks than their more familiar cousins, the egrets and “day” herons. Their resting posture is normally somewhat hunched making them look like elegant gargoyles, but when hunting they extend their necks and look more like other wading birds (from http://en.wikipedia.org/wiki/Black-crowned_Night_Heron accessed August 31st, 2013.)
Immature Black Crowned Night Herons have dull grey-brown plumage on their heads, wings, and backs, with numerous pale spots. Their underparts are paler and streaked with brown. The young birds have orange eyes and duller yellowish-green legs. These birds stand still at the water’s edge and wait to ambush prey, mainly at night or early morning. They primarily eat small fish, crustaceans, frogs, aquatic insects, small mammals and small birds. During the day they rest in trees or bushes. Their name “Nycticorax“ means “night raven” which alludes to their nocturnal habits and loud raspy call. Both the Great Blue Herons and the Great Egrets also have a pretty memorable squawk that can scare the bejesus out of you with the Great Blue Heron winning the award for most frightening (at least to me). I really enjoyed listening to their calls at the Cornell Lab of Ornithology web site (http://www.allaboutbirds.org/guide/Great_Egret/id ) and hearing them over and over again, I may actually vote for the Snowy Egret for most alarming. Cornell perfectly describes the sight of a Great Blue Heron which we are fortunate to see frequently in Folgers Marsh ((http://www.allaboutbirds.org/guide/great_blue_heron/sounds):
“Whether poised at a river bend or cruising the coastline with slow, deep wing-beats, the Great Blue Heron is a majestic sight. This stately heron with its subtle blue-gray plumage often stands motionless as it scans for prey or wades belly deep with long, deliberate steps. They may move slowly, but Great Blue Herons can strike like lightning to grab a fish or snap up a gopher. In flight, look for this widespread heron’s tucked-in neck and long legs trailing out behind.”
Most of these birds stalk around very silently looking for fish, eels, and crabs to devour. Each one has a slightly different strategy. They are fascinating to watch and a study in patience. Snowy Egrets wade in shallow water to spear fish. While they may employ a sit-and-wait technique to capture their food, sometimes they are much more animated, running back and forth through the water with their wings spread, chasing their prey. The Great Blue Herons are very stately and slowly stalk or wait patiently by the sidelines. The Great Egrets tend to stand perfectly still and seem to be watching the fish out of the corner or their eye. They amaze marsh visitors who are unused to seeing such large birds. On a perfect morning or early evening, we may have 30-40 birds in the marsh, each stalking their own territory and taking advantage of the light to grab juvenile fish. You may recall, most fish have countershading to avoid this lightning death from above. They are dark colored on top to lend in with the mud and dark sand and whitish from the bottom to avoid bottom predators like other fish in deeper waters.
Edie Ray comes out frequently during her shorebird monitoring patrols to check the marsh for various birds and she lists what she sees on our sign in sheet, so make sure to check for that information when you come to the Nantucket Field Station. And if you are in the neighborhood on Saturday September 7th, some to our classroom at 180 Polpis Road from 4:00-6:00 pm to hear two lectures, one on the History of the Field Station by Dr. Dick Gelpke and one by me on Nantucket Field Station Science.
The Nantucket Conservation Foundation has recently upgraded their web site and has an excellent link describing our islands salt marshes found at https://www.nantucketconservation.org/stewardship/habitat-types/salt-marshes/
The Linda Loring Nature Foundation Birding Festival is scheduled for October 17-20; they will be able to show you some of the shorebirds in the area then. More information here at http://www.llnf.org/index.php?id=68
Other resources: for this article include:
Nantucket Conservation Foundation description of the Nantucket Field Station https://www.nantucketconservation.org/property/nantucket-field-station/
Mass Audubon “Anthropogenic effects on the distribution and abundance of breeding salt marsh birds in Long Island Sound and New England” September 2001: http://www.massaudubon.org/PDF/Grassland/lis_final_rep.pdf
All links above live and accessed on September 1, 2013.