[Illustration: Crane’s Beach Diorama, Museum of Science]
LIFE IN THE SHIFTING DUNES
_A popular field guide to the natural history of Castle Neck, Ipswich,
Massachusetts, with attention to the unusual ecological relationships
peculiar to such an area_
BY LAURENCE B. WHITE, JR.
_Museum of Science, Boston_
_Illustrated by_ HENRY B. KANE
A PUBLICATION OF THE MUSEUM OF SCIENCE, BOSTON
Copyright, 1960,
by the Museum of Science, Boston
All rights reserved. This book, or parts thereof, may not be reproduced
in any form without permission of the publishers.
Library of Congress Card Number: 60-8980
Printed in the United States of America by
The Murray Printing Company
Forge Village, Massachusetts
PREFACE
This popular field guide to Castle Neck, Ipswich, Massachusetts, was the
inspiration of Mr. Cornelius Crane, who has summered there since
boyhood. Two years ago, Mr. Crane asked us if we would be willing to
undertake a survey of this typical dune area if funds were made
available for the study. We were delighted to cooperate in the project,
and our Education Department undertook it with real enthusiasm.
Some preliminary work was done in 1957, but during July, August, and
part of September, 1958, Laurence B. White, Jr., of our Education staff,
and Geoffrey Moran, his assistant, moved to Castle Neck. It is Larry who
has compiled this field guide.
Larry has been associated with our Museum since his Junior High School
days, when his consuming interest in natural history made him an almost
daily visitor, and later a valued Education Department volunteer. Now,
after his graduation from the University of New Hampshire, where he
majored in Biology and Education, he has joined our permanent staff. I
recount this only to point out that this study was undertaken by a born
and bred New England naturalist who enjoyed every minute of his work on
it.
Finding a little cottage on the side of a marsh on the road to Little
Neck, Larry and Jeff took it over as their combined summer residence and
laboratory, and spent the July and August weeks in Thoreau-like
exploration of the beach and dunes, the swamps and woodlands of Castle
Neck. Their personal relationship with the living things on the Neck is
feelingly reflected in this guide: sympathy with the heroic struggle for
survival on the dunes; admiration for the hardihood of the
little-admired Poison Ivy; amusement with the odd ways of the Common
Barnacle, which “goes through life standing on its head and kicking food
into its mouth with its feet”; and exasperation with the mischievous
practice of noisy Crows, who delight in wrecking an Owl’s daytime sleep.
It is perhaps because of this perceptive quality of understanding that
Larry’s report of the survey has readily adapted into a popular field
guide, directing the curious into a fascinating exploration of the “heap
o’ living” going on under our very noses and all but ignored by most of
us. This guide is not intended as an exhaustive research work or a
listing of all the living things to be found on Castle Neck. Rather, it
purposely addresses itself to natural history readily observable by
visitors with sharp eyes and reasonable patience. When a rarity is
included like the Ipswich Sparrow, it is only to indicate that such
unusual thrills await the discoverer—occasionally!
[Illustration: Deer Tracks in the Sand.]
While this guide serves as a reminder to those engaged in the study of
ecology that this is a rich area for serious investigation, the amateur
naturalist or the casual beach visitor, primarily on hand to sun, swim,
or picnic, may use it to make his stop on the Neck more meaningful.
Knowing, for instance, that Hog Island is a drumlin (a pile of debris
deposited in the Great Ice Age) adds enormous interest to the
surroundings. Larry’s guide is compiled with the understanding eye and
heart of an able and enthusiastic young naturalist. It invites you to
look over his shoulder as he investigates his finds, and tempts you to
further exploration on your own.
The analysis of the infinitely complex relationships of living animals
and plants to their environment, and to one another, is a relatively new
science. People with a strong desire to know more about the great sea of
life surrounding them have a real opportunity to contribute valuable
observations to ecological knowledge. You may very well be one of these!
Bradford Washburn
Director
Museum of Science
Boston, Massachusetts
ACKNOWLEDGMENTS
The author is first and foremost indebted to Mr. and Mrs. Cornelius
Crane for their unfailing interest in the preparation of this field
guide, and to members of the Museum staff who collaborated to edit and
produce it. Among these were Norman D. Harris, Director of Education,
Gilbert E. Merrill and Chan Waldron of the Education Department, Miss
Caroline Harrison, Director of Public Relations, and Mrs. Christina
Lopes and Mrs. Margaret Jordan of her department. Invaluable also in
preparation of the manuscript was the careful final editing of Miss
Helen Phillips, Houghton Mifflin Company.
Especially is the author grateful to the following for advice and
comment on various chapters: Clifford S. Chater, Assistant Professor,
Entomology and Plant Pathology, Waltham Field Station; Dr. Norman A.
Preble, Mammalogist, Northeastern University; J. Phillip Schafer,
Geologist, U. S. Geological Survey; Colonel E. S. Clark, Curator of
Marine Life, Peabody Museum of Salem, and Dr. Stuart K. Harris,
Department of Botany, Boston University.
L.B.W.
CONTENTS
Preface v
1. The Shifting Dunes 1
2. An Introduction to Dune Ecology 5
3. Plants on the Dunes 10
4. Life at the Edge of the Sea 19
5. Insects and Their Kin 33
6. Meeting the Mammals 50
7. Wings over the Sand 58
8. Now It’s Up to You—Check List for Your Discoveries and Field
Notes 69
[Illustration: Tree-topped dune.]
Chapter 1
THE SHIFTING DUNES
Surprising as it may seem, there was a time when many of our most
beautiful beaches, the Castle Neck area included, were far inland from
the edge of the sea. This was about a million and a half years ago, when
the sea was at a lower level than it is today. In fact, a great many
changes have helped to form the beaches we see and enjoy now. Of them
all, the one brought about by the Ice Age was probably the most
influential. It was some 30,000 or 40,000 years ago that New England was
overwhelmed by the final advance of a great continental ice sheet. It
came from the northwest, and as it inched its way toward the ocean it
pushed chunks of rock and great quantities of soil along with it. The
rock was continually breaking up as it was shoved forward under the ice.
This last glacier covered New England for thousands of years. When it
melted, all the debris it had been moving along like a giant bulldozer
was left deposited irregularly over the land, some debris perhaps a
hundred miles from original location. In addition, the water from the
melting ice swept finer sands and gravels along, depositing them over
land areas and in lakes and bays.
In some places, streamlined hills of debris had been built up under the
ice. Later, as the ice melted, they became exposed. They were shaped
like the bowl of an inverted spoon, and we call them “drumlins.” Hog
Island, to the south of Castle Neck, is a perfectly preserved example.
From its shape it is easy to tell which way the ice was moving. The
steeply sloping end of its long axis is toward the northwest, the
direction from which the last ice sheet came. All drumlins are not so
easily spotted. About a mile southeast of Castle Hill you will see a
hill that looks like an enormous sand dune. It is the highest point on
the Neck, about eighty feet, and it, too, is a drumlin. Once it
protruded out of a shallow bay that had formed as the ice melted.
Modified by the erosion of the waves and veneered with windblown sand,
this drumlin by now has quite lost its characteristic shape.
In the general Boston area many drumlins were uncovered as the ice
melted; some of them are such well-known landmarks as Beacon Hill,
Bunker Hill, or Breed’s Hill. Along the coast, as the sea level rose,
the drumlins there were surrounded by water and became islands. On the
sides exposed to the sea they were eroded by the waves, and the eroded
materials collected to form spits. Other sands and gravels carried by
longshore currents were added, and, by-and-by, in some cases these sand
spits connected one drumlin to another. It was just such a modification
of three separate drumlins that formed Castle Neck.
While the Neck was thus taking shape, the glacial debris and outwash
sands that had been deposited in New Hampshire and at the mouth of the
Merrimack River were being picked up and carried southward by the
prevailing currents. Finally this material was wave-tossed onto the
newly created beach at Castle Neck, some of it being lifted and carried
farther inland. In this way, except for a few protected spots behind the
drumlins, the entire area became blanketed with sand. The shape of the
Beach as we see it is the result of this ever-continuing modification,
the work of wind and waves.
It was on the protected back side of the drumlins that plants first took
hold. Since the drumlins were formed from fertile soil scraped from rich
inland areas and carried here by the ice, the same kinds of plants
sprang up on them—Aspens, Pines, Gray Birches, shrubs, and grasses—as we
often see today taking over some abandoned farmland. As these early
plants died, the soil was further enriched to stimulate even more and
different plant life. In fact, at one time much of the dune area was a
fertile spot, abounding with all sorts of plants and animals. In certain
places on the Neck today, very fertile soil can be found just a few feet
under the sand, evidence that here was once a rich farmland.
The broad flat areas of sand on the Beach were very susceptible to the
whims of the wind. Now and then, as the wind eroded the sand particles
from one place, and blew them to another, it piled them up against the
base of some beach plant. Collecting here, the sand began to form a
gentle slope with a sharp drop-off downwind. Continuation of this action
sometimes built up a huge mound, which we call a dune.
This process of erosion and deposition still goes on. Usually you can
tell the general direction of the prevailing wind by observing which way
it builds the gentle slope as it piles the sand into ripples or mounds.
If you should mark a dune’s position today and return in several years,
you might find that the dune had moved several yards from its original
position. Dunes move slowly downwind, such movement being termed
“migration.” With a normal dune, during windy periods the sand is blown
up its gentle slope and dropped over its crest, whence it slides down
the lee side. In this way the dune migrates with the wind.
THE FUTURE OF CASTLE NECK
Eventually, of course, the dunes might migrate the entire length of the
Neck and again be blown into the sea, which would carry the sands
farther south, mayhap to become part of Coffin and Wingaersheek Beaches.
In fact, we might expect the eventual removal of the entire Neck if sand
wasn’t constantly being added from similar erosion going on farther
north. Obviously there is a very delicate balance here, adding and
subtracting sand. The future of Castle Neck is entirely dependent upon
the sand supply from the north. Too little may eventually diminish
Crane’s Beach; while an increase could create an even larger and more
beautiful Neck. Actually, it is impossible to predict the future of a
beach, at the mercy, as it is, of changes in any of the several factors
controlling its form—sand supply, waves, currents, and position of sea
level. Anyway, what has been so long taking shape will not be altered
drastically overnight. As a matter of fact, if you really wish to know
the future of Crane’s Beach, you will have to be patient. Another
million and a half years will probably tell the story!
GEOLOGICAL DISCOVERIES YOU CAN MAKE
_Ventifacts_
These small, faceted pebbles found in the dunes have been blasted by the
windblown sand. They show the powerful abrasive action of the wind. Most
of those you will find here were faceted just after they had been
deposited by retreating glacial ice. A migrating dune or a blowout in
the sand has left them uncovered.
_Erratics_
Large rocks occasionally found in the dunes are called “erratics.” In
this world of tiny particles they appear very much out of place, but
they were carried here by the glacier a million years ago. They have
been uncovered by the migration of some dune.
_Fulgurites_
Occasionally lightning strikes the sand, fusing it into a little tube or
ball of glass. These fulgurites have been found here but are very rare
and a real “discovery.”
_Glacial Till_
The original soil deposited by the glacier may be seen by digging into
the sand at the drumlin. Such rocky soil is quite surprising to people
who think the beach is nothing but a big “sand pile.”
_Garnets_
Examine a handful of sand. You will find that it consists of
light-colored particles (mostly Quartz) and of black particles. Under a
microscope many of these dark particles look like little gems. They are
actually a deep red and are true Garnets. Large Garnets are used as gem
stones, small ones for sandpaper—further proof of the abrasive ability
of windblown sand.
_History in the Sand_
In your handful of sand you may find particles that are neither Quartz
nor Garnet. Minerals such as Feldspar, Biotite, Mica, Magnetite,
Hornblende, and others can be identified by the geologist and are a clue
to the original type of rock over which the glacier moved.
_Beach Porcupines_
These are hard-packed balls of twigs and grasses. Loose vegetable matter
is very light and may be blown along by the wind for many miles. As it
goes it adds other vegetation to itself, until packed into a very tight,
hard ball. It may also get its start in the water by being whirled into
a tiny ball; and later it is thrown onto the beach, to begin rolling
along. A most curious souvenir!
MORE ABOUT THE DUNES
The face of the land is a storybook waiting to be read. The following
books will help you piece together some of the story:
Henry Curtis Ahl, _Dunes and Beaches of Essex County_. Boston:
Massachusetts Audubon Society, 1949. $.25
N. E. Chute and R. L. Nichols, _Geology of the Coast of Northeastern
Massachusetts_. Massachusetts Department of Public Works and
U. S. Geological Survey Cooperative Geologic Project, Bulletin
#7. Boston, 1941. Out of print. Available in Museum of Science
Library.
John Henry Sears, _The Physical Geography, Geology, Mineralogy and
Paleontology of Essex County, Massachusetts_. Salem, Mass.:
Essex Institute, 1905. $6.00
Charles Wendell Townsend, _Sand Dunes and Salt Marshes_. Boston: L. C.
Page, 1913. Out of print. Available in Museum of Science
Library.
——, _Beach Grass_. Boston: Marshall Jones, 1923. $3.50