BIRDS OF NANTUCKET
THE CHALK LINE BIRD
by Kenneth Turner Blackshaw
What an unfortunate nickname! But we'll get into that later. This bird is also known as 'fly up the creek!' It's a bird I know more from its call than from its appearance. You hear this strident 'keee-ow' sound and look around and there is a short-tailed, crow-sized bird flying away - up a creek?

Green Heron

The literature says it is a favorite of the country child and the pond fisherman. If you are one of these, this bird is probably your friend. If you have a goldfish pond, it may seem more like your enemy.

Our bird this week is the Green Heron. From 1983 to 1998 we had to think of it as the 'Greenbacked' Heron but that was just to keep us on our toes. At that time this bird had been 'lumped' in with an Asian and South American species. Now our North American bird has been split out again.

Only in certain lights do you see any green at all and that is from the back. The scientific name is Butorides virescens, meaning a greenish bird that resembles a bittern. Mostly you see a large, dark bird flying off and someone in the group calls out "Green Heron."

When we think of a heron most of us conceive that large, long-necked bird that poses, immobile at the edge of a pond, the Great Blue Heron. There are actually 12 species of herons here in the eastern USA in a family that includes herons, egrets, night-herons, and bitterns. Family, by the way, is the next largest grouping above genus when we are classifying living things. There are two other living species in genus Butorides but our Green Heron is the only one to be seen in North America.

Rather than green, what stands out more is the chestnut color on the neck. There are streaks down the front of the throat and the top of the head is nearly black. Another nickname this bird goes by is 'rubberneck.' Most of the time Green Herons appear neckless but that is because the head is drawn back on its shoulders. When pouncing on prey or if startled, a surprisingly long neck extends.

Green Herons don't tolerate cold weather well and are not found north of Florida in the wintertime. They migrate at night and quickly cover long distances when the urge takes them. John James Audubon wrote in 1840 about seeing them descend in groups of 20 to 50 into the treetops within an hour of sunrise. Then at dusk they would launch into the air again and fly all night. This movement would be a marvelous

sight to see.

We expect to see Green Herons here from May through September. They have nested in such diverse places as Quaise Marsh, near Second Bridge at Long Pond, and in the State Forest. This tells you something of their nest site requirements.

Their courtship behavior is a bit astounding. Mostly these birds skulk around in hunchedover posture. But when attempting to impress a potential Mrs. Heron, they suddenly hop backwards and jump up and down, first on one foot then the other.

Normally these herons nest in trees 25 to 40 feet up in the air. Their nest is loosely woven of sticks, often so flimsy you can see right through it. They incubate their four or five eggs over two weeks before the downy young hatch. Quite quickly they leave the nest, not to fly but to clamber awkwardly around the tree. They grasp branches ahead of them with an appendage known as a 'bastard wing,' which is a vestigial claw that harkens back to their reptilian ancestors. Birders know this part of the wing as the alula, used by most birds in flight to alter the airflow around the wing.

Green Herons also have a web between their middle and outer toes that ties back to an earlier ancestor. The youngsters are described to swim around like little swans!

If you are fortunate enough to see one of these birds it will appear small and dark, often horizontally oriented as it skulks along the edge of a saltwater marsh or even a vernal pool in the woods. Last year Nantucket's 'bird rangers' doing a Maria Mitchell birdathon fundraiser were surprised to see one slinking amongst the roots in a wet depression just off Polpis Harbor Road. This bird gave us an additional species and probably garnered us another $20 for charity.

And the 'chalk line' bird? When startled, their first thought is flight. Perhaps an unconscious thought is, 'I have to be lighter to fly quickly,' so an impressive stream of white matter often is ejected from the rear of these birds on take-off. Green Herons have other nicknames

but 'chalk line' is the least objectionable. I

George C. West creates illustrations for these articles. The Maria Mitchell Association sponsors bird walks on Tuesday and Saturday mornings starting at 8 a.m. from the corner of Vestal and Milk Streets. There is a fee. Ask Ken a question at: kenandcindy1@comcast.net