The 'Two - Ten - Two' Principle
BIRDS OF NANTUCKET
by Kenneth Turner Blackshaw

A 'Lady of the Evening' or a 'Night Crow?'

Perhaps it's a matter of perspective?

It makes me think of what my friend Joe used to refer to as the 'Two - Ten - Two' principle. As one sits in a bar and time passes, the 'Twos' become 'Tens' around two in the morning. I'm sure you are realizing at this point that this must have something to do with birds.

This week's bird is a water bird - a heron, but a different type from the long-necked Great Blue most people would think about. This bird is a nightheron. You get the idea you might not see one in the daytime, but they are crepuscular rather than nocturnal, so they are most active at dusk or dawn.

Most of Nantucket's night-herons are the Black-crowned variety. You often hear them flying right over town in the late evening. My grandmother called them 'Woks' since that's what their call sounds like as they call back and forth to one another.

This night-heron is much rarer and has only been found here over the past 40 years - the Yellow-crowned Night- Heron, Nyctanassa violacea - the violet lady of the evening. The more common Black-crowned Night-Heron goes by Nycticorax nycticorax, literally a night crow. Over the years the ornithological mavens at the American Ornithological Union have flipped the Yellow-crown from Nytanassa to Nycticorax and back again, hence the question at the beginning of this article - a crow or a violet lady or a crow - an avian 'Two - Ten - Two.'

Night-herons are crow-sized herons. When you see them flying, they look like round-winged crows. One person reported a flock of owls flying over the Stop and Shop one evening and we knew this had to be a flock of Black-crowned Night-Herons on their way to feeding at the edge of the harbor.

You may think that Yellow-crowned Night-Herons would differ by having yellow at the top of their heads and you'd be right, at least in the breeding season. The yellow tends toward cream and it turns white during most of the year. They are darker birds than the more common Black-crowns, being gray below instead of white and having black faces with white cheek patches. Both species are speckled brown for the first year, but the Yellow-crowns differ by showing some yellow on their bills.

But plumage aside, Yellow-crowns are just ganglier. In flight their long legs and feet trail noticeably behind their tails. This is a good point to watch for even with the confusing brown teenagers.

Behavior is another useful aspect. Both night-herons like to eat things associated with the water - small fish, shrimp, frogs and crayfish, but Yellowcrowns tend to like crunchy items better. They spend more time in the mangroves chasing crabs. On the west coast of Florida lives a spooky critter called a "Ghost Crab." These mainly nocturnal white crabs live in burrows on the shelly Gulf beaches and have the ability to glide rapidly sideways and disappear into their holes. Often we see a Yellow-crown poised patiently waiting for the tenant to emerge from its burrow. They break them apart and swallow all the pieces.

Although unknown in these climes when Griscom and Folger penned "The Birds of Nantucket" in 1948, over the last half of the 20th century this species, along with several others, the Snowy and Great Egrets and the Little Blue Heron, have been working their way northward reaching our summer shores. Yellowcrowns have been added to our checklist as 'rare' from May into September each year and we wonder when a nest will be found.

Right now their nesting territory goes from Southern New England to down around the Gulf shores to Texas and across the Caribbean. These short-necked herons build a stick nest reminding one of a crow's and that's where they lay their three or four pale green eggs.

In early June this year a single adult Yellow-crowned Night-Heron was reported along the shore of Long Pond near Massassoit Bridge. In other years there have been summer records in the Quaise area. The brushy-edged ponds in that area are likely spots where a nest might be found. Historically the species has nested several places on Cape Cod and even as far north as Cape Ann.

The most likely time to see a Yellowcrown on Nantucket is later in the summer season when so many longlegged waders wander about after completing their nesting activities. Any young brown night-heron needs to be examined carefully to make sure it's not a Yellow-crown. Look for yellow on the bill and larger white spots on the wings. If you see one in flight, look for the longer protruding legs. Then think of the 'Two - Ten - Two' principle and wonder if you have a 'lady of the evening' or just a 'night crow.'

George C. West creates illustrations for these articles.

The Maria Mitchell Association sponsors bird walks on Tuesday and Thursday mornings at 6:30 a.m. and Saturday mornings starting at 8 a.m., from the corner of Vestal and Milk Streets. There is a fee for non-members.

To hear about rare birds, or to leave a bird report call the Massachusetts Audubon hot

line at 1-781-259-8805. I