Coastal Great Blue Heron populations of the Michigan Great Lakes

[From the U.S. Government Printing Office, www.gpo.gov]

COASTAL GREAT BLUE HERON
POPULATIONS OF THE MICHIGAN GREAT LAKES

William C. Scharf
U% Department of Biology
Northwestern Michigan College
-D Traverse City, Michigan 49684
0- (616) 922-1275

This dociiment was prepired in part
through f in'anc i7a I ass istpnco Provided by:'
tl-e Coast
a! ZO?-,e NAtInAvernent Act of 19712
@)v the Cf@f;cc.- @"f Cn@ 7,
-'sfal Zone @A,'In@@gament,
National Ocamig mid Atrro-spharic Adminigtra'tion

QL
696
C52
S33
1988

ACKNOWLEDGMENTS

I wish to thank the following people for
their assistance in the producing of this
report:

Donald DeRuiter, floatplane pilot;
Warren Alward, Jeanette Bailey and James
Ribbens, Division of Land Resources Programs,
Michigan Department of Natural Resources; Dr.
David Ewert,' Nature Conservancy, access to
Hat Island; Judith Reich, Susan Sheffer and
Kathy Graves, report preparation.

TABLE OF CONTENTS

Introduction ......................................... Page I

Methods .............................................. Page 2

Results .............................................. Page 4.

General ......................................... Page 4

Site by Site .................................... Page 6

Discussion and Conclusions ........................... Page 6

Literature Cited ..................................... Page 9

Tables 1 - 5 .......................................... Page 10

Figure 1 ............................................. Page 26

Mapsof Selected Heron Colonies .......................... Pages 27-41

Black and White Photographs (33) ... (submitted separately)

Marked DNR Maps .................... (submitted separately)

INTRODUCTION:

Coastal nesting Great Blue Hero ns choose islands and

peninsulas in the Great Lakes to escape human disturbance.

The very isolation the herons seek makes the knowledge of

their current populations and status of interest in assessing

both the health of the species and it's habitat. This study

shows-the changes in populations of costal and island nesting

colonies of Great Blue Herons (Ardea herodius.) and,

incidentally, Great Egrets (Casmerodius albus) since the last

complete census in 1976 and 1977 (Scharf, et al. 1978 and

Scharf 1979). The realization that Great Blue Heron colony

size and location is not static, but changes with the

dynamics of vegetation succession hastened by bird feces has

long been recognized (Weseloh and Brown 1971, Soots and

Parnell 1975, Wiese 1978, Mathiesen and Richards 1978, and

Scharf et al. 1978). Other factors emphasizing the need for

this study are changes in land use such as urbanization,

vacation home construction, and lumbering which have

eliminated both inland and costal heronries.

The study area includes the entire four Michigan Great

Lake coasts, the three connecting rivers, and Lake St. Clair.

These coasts were searched up to 1 km inland. The location,

size and changes in colonies along with the vegetation and

substrate data presented here are essential to the zoning of

Environmental Areas by the Michigan Department of Natural

Resources, Land Resources Division.

METHODS:

I used a Cessna 180 floatplane to locate, photograph,

and count heron nests from the air. Then, at most sites, I

landed to make ground counts of nests, and identify and

measure nest trees. While on the ground I recorded the

ground cover species assessed the condition of the nest

trees, recorded the substrate, and generally evaluated the

status of the colony. Click-type mechanical tallying devices

were used for counting both in the air and on the ground.

Nesting phenology and behavior were estimated by

previous experience.and also correlated with the Southern

Michigan study by Cotrille and Cotrille (1958). Latitudinal

differences in nest.phenology required that I begin my first

visit to the southerly colonies on 18 April, 1987. My last

visit to the most northerly colonies was on 08 July, 1987.

In each case, the goal was to visit each colony twice. The

first visit was timed from the peak of egg laying to

incubation, which was usually before heavy leaf emergence

which could screen the nests from view. The second visit was

during the late chick-rearing, pre-fledgling period.

The problem of layering of nests, in aerial counts,

which leads to hidden, uncounted nests, even without leaves,

is acknowledged. However, during this season.I have found

that there can be difficulty with gaining a complete count of

nests from the ground caused by nest layering and the

inability of,the ground observer to find far-flung nest

trees. It is apparent that the nest counter on the ground

could miss whole portions of a colony which can be easily

seen from the air. There is also a similar nest obscuring

factor due to the layering of nests viewed from the ground.

Therefore, the use of combined aerial and ground counts, as

with most of the colonies reported herei is probably the best

technique for overall accuracy.

Black and white 35 mm film with 125 ASA was used for

maximum contrast of nests in aerial photography. Most photos

wer e taken on the first or second pass over a heronry to

photograph the greatest numbers of birds present in the

colony. Photos were usually taken at an altitude of 150 to

250 m above the ground and the plane was banked to give as

near a vertical view of the colony as possible. Over 200

exposures were taken. Thirty two of the better quality

photos representing a wide variety of colonies were printed,

and accompany this report (Table 5). The rest of the

negatives are catalogued and available as prints upon

request.

A diameter breast height (DBH) tape was used to measure

nest trees. The spacing of nest trees was measured with a

.10 m rope and, where applicable, the rope was used to

establish 100 m2- quadrants to quantify the density of the

understory herbs and shrubs. The quadrant technique was used

less than anticipated this year because of the many

extremely, sparsely vegetated colonies, and others which were

so dense with woody vegetation that they made portions of the

colonies inaccessible.

RESULTS:

Population Trends:

Coastal and island Michigan Great Blue Heron populations

have shown a 70.8% increase (Table 1) since the last census

ten years ago (Scharf et al. 1978 and Scharf 1979).

Occupancy rates in colonies were nearly complete. Seldom

.were there nests which could be identified as abandoned

either from the air or ground (Table 4). Active nests are

identified because of their fecal whitewash or the presence

of eggs, chicks, or incubating adults. In addition, only two

colonies have been abandoned since 1976-77. They are Stoney

Island in the Detroit River, which has been changed by

industrial activity and Scammon point, which may have been

affected by recent residential construction in the nearby

Drummond Island area (locations on Tables 1 & 2 and Figure

1).

.The turnover rate (Erwin 1977 and Erwin et al. 1981)

calculated for the entire study area is only 5.2% per year

for the ten year interval since the last census. This

turnover rate indicates a stable to growing population. I

find further analysis of the sub-regional increases by

turnover rate misleading because of the large population

growth in new colonies, but it can be seen, by scanning Table

1, that new colonies are concentrated in two sub-regions.

One of the sub-regions of population increase extends from

the Eastern Mackinaw Straits area.of Lake Huronup the St.
Mary's River to Bay Mills Island in Lake Superior, just west

of.Sault St. Marie. The other increasing sub-region includes

most of the colonies numbered 27 thru 35 in Northern Lake

Michigan from the Straits west to the Green Bay - Bay de Noc

(Tables 1 & 2).

At colonies where increases in numbers of herons have

occurred, there appear to be two mechanisms of increase

within the colony. In southerly area, such as Dickinson and

Hesterman Islands, which have long-lived, mature hardwood

nest trees and relatively rich deep soils there has been a

trend toward greater numbers of nests per tree; up to 10-12

nests in some cases. In more northern colonies, where short-

lived trees are rooted in shallow, loose, sandy or rocky

,soils, colony expansion has been by expanding the area to

more individual trees. Ultimately, however, the causes of

this increase must indicate the availability of foraging

habitat, and the degree of protection the species enjoys. It

is unknown, at present whether the growth in coastal colonies

may be at the expense of declining inland populations.

Individual Colony sites:

The results of vegetation analysis and site by site

evaluation are given in Table 4.

DISCUSSION AND CONCLUSIONS

Whether or not, the present trend toward increasing

coastal heron populations is due to their continuing legal

protection and the maintenance of foraging habitat, or

because of increasing human pressure and disturbance at

inland sites, I endorse the recommended buffer zone of 250 m

around nesting colony sites to support the vegetation and

accessibility by the herons (Short and Cooper 1985), as a

minimum comfort zone for the birds. The recommendation of a

100 m buffer around foraging areas seems logical, but the

lack of documentation to support it in Michigan, and relative

isolation of the wetlands involved in this study combined

with other legal protection for wetlands makes specific

protection for heron foraging improbable.

In some instances, the flight distances to foraging

sites of the island nesting herons may be as far as 10-20 km.

Gibbs et al. (1987) have shown the positive correlation

between island heronries in Maine and the proximity,of

wetlands. They also speculate that food competition between

colonies limits their size. The flight distances to forage

and extreme isolation of the heronries described here serve

to underscore the importance of these sites to the

maintenance of the species in Michigan coastal waters. That

is, many of these colonies represent the last resort for

nesting herons, if pressures develop on mainland colonies. In

such a worst case scenario recreation on the islands and near

the foraging areas would have to be curtailed to maintain

their productivity. The absence of islands and coastal

wetlands explains why the area along the central to

southeastern Lake Michigan Coast has no coastal heronries.

One of the unexpected findings of this study is the

apparent stability of the vegetation and age of the trees in

some of the more southerly.colonies. The toxic effects of

feces apparently is not of great importance to long lived

tree species such as oak, hickory, and maple. The shorter

lived species such as aspens and birch, are more susceptible

to over fertilization, and in northern areas where they are

important nest trees, the soils are shallower and more porous

which leads to more frequent blown downs.

The health of coastal heronries seems assured at present

with a few exceptions noted in Table 4. Most of the

exceptions represent the development of vacation homes,

boating, fishing, and hunting activity in or near heronries.

While these are acceptable human pursuits, it is doubtful

whether they are necessary in area which could destroy

nesting or forag ing habitat of this important native bird

species. Continued monitoring of this resource is important

to insure its perpetuation and stop intrusions before the

damage is irreparable. Monitoring is done regularly in Maine

(Gibbs et al. 1987), Minnesota (Mathieson and Richards 1978),

Montana (Thompson 1982), and Pennsylvania (Dunn and Brucker

1986).

LITERATURE CITED

COTTRILLE, W.P., and B. D. COTTRILLE. 1958. GREAT BLUE
HERON: BEHAVIOR AT THE NEST. University of Michigan Museum
Zoology. Ann Arbor. Misc. Publ. 102.
DUNN, J. P. and E. BRUCKER. 1986. PROJECT ANNUAL REPORT
COLONIAL NESTING BIRD SURVEY. Pennsylvania Game Commission
5 P.

GIBBS, J. P., S. WOODWARD, M. L. HUNTER, and A. E.
HUTCHINSON. 1987. DETERMINANTS OF GREAT BLUE HERON COLONIES
DISTRIBUTION IN COASTAL MAINE. 104:38-47.

MATHIESEN, J. and A. RICHARDS. 1978. STATUS OF GREAT BLUE
HERONS IN THE CHIPPEWA NATIONAL FOREST. THE LOON. 50:104-106.

SCHARF, W. C., G. W. SHUGART, M. L. CHAMBERLIN. 1978.
COLONIAL BIRDS NESTING ON,MAN-MADE AND NATURAL SITES IN THE
U.S. GREAT LAKES. Rep. WES-TR-D-78-10. U.S. Army Eng. Waterw.
Exp. Stn. Vicksburg, Miss. 140 pp.

SCHARF, W. C. 1979. NESTING AND MIGRATION AREAS OF BIRDS OF
THE U.S. GREAT LAKES (30 April to 25 August, 1976). U.S. Fish
and Wildlife Serv. Off.. Biol. Serv. FWS/OBS-77/2. 113 pp.

SHORT, H. L. and R. J. COOPER. 1985. HABITAT SUITABILITY
INDEX MODEL: GREAT.BLUE HERON. U.S. F.W.S. Washington, D.C.
Biol. Rep. 82. (10.99). 23 pp.

SOOTS, R. F., and J. F. PARNELL. 1975. ECOLOGICAL SUCCESSION
OF BREEDING BIRDS IN RELATION TO PLANT SUCCESSION ON DREDGE
ISLANDS IN NORTH CAROLINA ESTUARIES. Univ. North Carolina Sea
Grant Program Publ. UNC-75-27. North Carolina State Univ.,
Raleigh. 91 pp.

THOMPSON, L. S. 1982. A 1979 CENSUS OF GREAT BLUE HERON
COLONIES IN MONTANA. Proc. Mont. Acad. Sci. 41:23-27.

WEELSOW, D. V. and R. T. BROWN. 1971. PLANT DISTRIBUTION
WITHIN A HERON ROOKERY. Am. Midl. Nat. 86:57-64.

WIESE, J- H. 1978. HERON NEST SITE SELECTION AND ITS
ECOLOGICAL EFFECTS. WADING BIRDS. Natl. Audubon Soc. Res.
Rep. 7:27-34

TABLE 1

GREAT BLUE HURON and GREAT EGRET (GE)
COLONIES AND NUMBERS OF NESTS IN THE MICHIGAN GREAT LAKES

COLONY NAME LAT. AND LONG. 1976-77, 1987

1. Stoney Is. 4206-08308 14 + 29GE 0
2. Dickinson Is. 4237-08238 57 + 2GE 113 + 22GE
3. Hesterman Is. 4350-08326 0 125 + 6GE
4. L, Charity Is. 440 '0-08328 0 0 3GE
5. Bird Is. 4453-08320 0 3
6. Scare Crow 4455-08320 24 27
7. Gull Is. 4503-08314 33 55
8. South of Calcite 4525-08346 0 1
(Rogers City)
9. Big St. Martin Is. 4558-08426 0 38
10. Goose Is. 4555-08426 75 .87
11. Gravely Is. 4558-08414 11 9
(Crow Is.)
12. Saddle Bags Is. 4557-08402 32 32
13. Gravel Is. 4556-08346 4 22
14. Scammon Pt. 4556-08338 40 0
15. Cedar Is. 4605-08345 0 28
16. Round Is. 4606-08401 39 23
17. Love Is. 4606-08359 0 35
18. Roach Pt. 4612-08409 0 12
19. Moon Is. 4613-08410 0 23
20. Gem Is. 4626708411 43 44
21. Rock Is. 4623-08409 27 22
22. Bay Mills Is. 4627-08431 0 22
23. Williams Island 4629-08843 78 4
24. Huron Is. 4656-0880 0 53
25. Traverse Is. 4707-08816 62 89
26. Waugoshance Is. 4546-08504 33 26
27. St. Helena Is. 4552-08452 27 33
28. Hat Is. 4547-08518 3 7
29. W. Grape Is. 4547-08525 5 4
30. Squaw Is. 4551-08536 0 48
31. Epoufette Is. 4606-08513 32 21
32. L. Hog Is. 4604-08517 0 18
33. Big Gull Is. 4530-08643 0 19
34. St. Vital Is. 4548-08645 6 4
35. Round Is. 4545-08646 13 17

TOTALS 658 + 31GE 1064 + 31GE

TABLE 2

LOCATION OF'GREAT BLUE HURON COLONIES
BY TOWNSHIP AND RANGE
AND DNR AERIAL MAP AVAILABILITY

COLONY NAME

1. Stoney Is.
2. Dickinson Is. NO T2N, 15E
3. Hesterman Is. NO T17N, 9E
4. L. Charity Is. NO 19N, 8E
5. Bird Is. YES 29N, 9E
6. Scare Crow NO 29N, 9E
7. Gull Is. YES 31N, 10E
8. South of Calcite NO 34N, 6E
(Rogers City)
9. Big St. Martin Is. YES 41N, 3W
10. Goose Is. YES 41N, 1W
11. Gravely Is. YES 41N, 5E
(Crow Is.)
12. Saddle Bags Is. YES 41N, R3E
13. Gravel Is. YES 41N, 5E
14. Scammon Pt. YES 41N, R6E.
15. Cedar Is. YES 43N, R5E
16. Round Is. YES 43N, R3E
17. Love Is. NO 43N, R4E
18. Roach Pt. YES 44N, R2E
19. Moon Is. YES 44N, R2E
20. Gem Is. NO 47N, 2E
21. Rock Is. NO 46N, 2E
22. Bay Mills Is. NO 47N, 2W
23. Williams Island
24. Huron Is. NO 53N, R29W
25. Traverse Is. YES 54N, 31W
26. Waugoshance Is. NO 39N, 6W
27. St. Helena Is. YES 40N, 5W
28. Hat Is. YES 40N, 6W
29. W. Grape Is. NO 39N, 9W
30. Squaw Is. YES 40N, 1OW
31. Epoufette Is. YES 42N, 7W
32. L. Hog Is. NO 42N, 8W
33. Big Gull Is. NO 38N, 12W
34. St. Vital Is. NO 39N, 20W
35. Round Is. NO 39N, 20W

TABLE 3

GREAT BLUE HERON
NEST TREES

COLONY NAME -NEST TREES-

1. Stoney Is. None
2. Dickinson Is. White Oak, Red Oak, Shagbark Hickory,
Elm (dead)
3. Hesterman Is. Ash, Birch (dead), Red Maple, White Oak
4. L. Charity Is. Plum
5. Bird Is. Ash (dead)
6. Scare Crow' Ash
.7. Gull Is. Cherry, Ash
8. South of Calcite Elm (dead)
(Rogers City)
9. Big St. Martin Is. Red Maple, Quaking Aspen
10. Goose Is. Birch (dead & live), Quaking Aspen, Ash,
Balsam Poplar
11. Gravely Is. Ash, Birch
(Crow Is.)
12. Saddle Bags Is. Birch, White Cedar.
13. Gravel Is. Birch, Ash, Aspen
14. Scammon Pt. All trees down
15. Cedar Is. Birch, Ash, Aspen
16. Round Is. Birch (live & dead), Balsam Poplar
17. Love Is. Birch & Ash, Spruce & Cedar
18. Roach Pt. Balsam Poplar, Cottonwood
19. Moon Is. Balsam Poplar, Ash
20. Gem Is. Elm (dead & live)
21. Rock Is. Elm (dead & live), Birch
22. Bay Mills Is. Red Oak
23. Williams Island Spruce (live & dead), Quaking Aspen (live),
Birch (dead)
24. Huron Is. White Pines
.25. Traverse Is. Birch (live,& dead), Red Maple, Quaking Aspen
26. Waugoshance Is. Yellow Birch, Quaking Aspen
27. St. Helena Is. White Birch (dead), Quaking Aspen
28. Hat Is. Birch
29. W. Grape Is. Ash
30. Squaw Is. Birch (dead & live), Quaking Aspen
@ 1. Epoufette Is. Aspen
32. L. Hog Is. Aspen & Birch
33. Big Gull Is. Birch
34. St. Vital Is. Cottonwood
35. Round Is. White Cedar (dead) & Birch

TABLE 4

VEGETATION QUALITY AND POTENTIAL BUFFER ZONE INTRUSIONS
for
COASTAL MICHIGAN GREAT BLUE HERON COLONIES, 1987

COL NEST TREE SPECIES AND UNDERSTORY BUFFER ZONE
MEAN SIZE, SAMPLE SIZE)

----- ------ ------

2. Red Oaks 60.9 cm DBH (4) Prickly Ash, Deer browsing;
White Oak 73.6 cm DBH - Muscle Wood, hunters blinds
Elm 47.4 cm DBH (3) Bedstraw, Highly popu-
Shagbark Hickory Moss, Violets, lous area;
55.8 cm DBH (12) Nettle, 15cm Presently
Tree height: 23-30 m water under adequate, but
.trees in April needs to be
dry by June. monitored

3. Red Maple 48.2 cm DBH (5) Moss, Iris, Seems safe,
Ash 33.0 cm DBH (2) Open water up except for
Dead Birch to 60 cm deep, possible il-
White Oak 35.5 cm DBH (1) May Apple, , legal harass-
Tree height: 20-28 m Nettles, Grape ment by the
Vines, Prickly population
Ash. Many of sport-
Snakes fisherman.

4. Wild Plum 10.1 cm DBH (1) Nettle, (+,-) 24
Tree Height: 7 m or less Burdock, Herb Herring Gulls
Robert found shot
here; presum-
ably this has
neg. impact
on herons and
egrets too.

5. Probably Ash about Bare Cobble Even though
20 cm DBH most trees are
Tree height: 15 m dead here,
there are
plenty that
could hold
more Great
Blue Heron
nests.' No
threat is
imminent to
this colony.

6. Ash and Elm Bare cobble Commercial
17.7 cm DBH (2) a few Nettles harvest of
Tree height: 15 m and Burdock. Carp trapping
is done here,
but that is
after the
nesting season
The Double-
crested Cormo-
rants have
gone from.
zero to 137
nests since
1976, but the
herons have
also increased
A few (2-3)
Black-crowned
Night Heron
usually nest
here too.

7. Cherry 16 cm DBH; and Varies from Much of the
Ash 18-35 cm DBH sand and cobble former woody
Tree height: 4-12 m to Ground Hem- vegetation on
lock and small this island is
Choke Cherry- blown down;
present nest
trees are dy-
ing and Cor-
morants are
taking others;
therefore, re-
cent increases
in Great Blue
Herons may be
only temporary
The island
seems fairly
safe from most
human intru-

sions.

8. Single large, dead Elm Edge of a This nest ap-
Tree height. 10 m marsh with pears to be
some open abandoned but
water. the foraging
area and abun-
dance of suit-
able nest
trees make
this site an
attractive one
for recoloni-
zation.

9. Red Maple Surrounded by No threats to
Quaking Aspen 15-40 cm DBH Cedar swamps; this heronry
Tree height: 10-15 m Some standing are evident;
water. the farm at
the northern
part of the
island seems
to have ample
fire wood, and
the heronry
would not be
suitable for
logging.

10. Live and dead Birch Some water to The Great Blue
35 cm DBH, some a depth of 45 Heron nesting
Dead Aspen 28.7 cm DBH cm; Jewelweed area on this
Ash, Balsam Poplar Nettles, Cow island has ex-
Density 25 stems/100 m2, Parsnip, Red pande'd greatly
and 3-4 stems Aspen/100 M2 Elder, high from 1976-77;
bush Cranberry, the takeover
White Cedar, of Cormorants
Red Osier Dog- of nest trees
wood, other on the South
areas are bare end has forc-
.because of ed the herons
over-fertili- north to
zation with healthier
feces. trees;

10. Continue com-
pletely dis-
agree that
there is a
zone which
could allow a,
structure to
be built here
without signi-
ficant nega-
tive impact on
the bird popu-
lations.

11. Ash and Birch See Detailed Two of the
map - this nests look a-
report. bandonded here

12. Birch and White Cedar See Detailed Despite the
map - this structure on
report. this land, the
heron popula-
tion persists.

13. Birch, Ash, Aspen See Detailed Population has
map - this increased 5
report. times 1976-77
numbers.

14. All trees down ----------- The demise of
this heronry
could be from
the nearby
residential
development.

15. Birch 26.5 cm DBH (5) Dense Balsam Deer and
Ash 28 cm DBH (8/100 m2), beaver are
Aspen 25 cm DBH plus Choke eating the
Balsam Poplar 22.3 cm DBH Cherry, White woody vegeta-
Cedar tangle, tion here;
Moosewood, Cur- possibly a
rant, Violets; moose present
and Ferns; here too! No
Jewelweed and threat to this
raspberry under isolated area.
trees where
whitewash hits.

Elm (dead) about Border of This is one of
30.5 cm DBH; White Cedar the few colon-
Birch about 25.4 cm DBH tangle of ' ies which is
Red Maple about Canada Yew and declining in
32 cm DBH fallen trees numbers; the
Tree height: 15-17 m in interior decline is at-
where heron tributed to
nests are; the loss of
See map in nest trees due
this report. to the death
and blow down
of the birch
and elm; this
seems to be a
natural sue-
cessional se-
quence which
is exaggerated
because of the
shallow soils
on the island.
If further,
human devel-
opment is pre-
vented, how-
ever, this
colony should
persist in its
reduced state
for some time
in the future.
The rise of
the Love Is.
(#17) colony
is probably a
result of the
decrease at
this colony.
That is, as
the trees at
one become un-
suitable the
birds moved to
the most suit-
able nearby
colony.

17. Dead (15 of 30 trees) ---------- This is
or dying White Birch probably the
20-30 cm DBH new" colony
A few nests in Black began after
Spruce and White Cedar decline of the
Tree height: 10-15 m previous one
(#16); Cedar as
the dying Birch
nest trees go
down there is
about 1/3 of
the island left
to place nests
in, and the
herons are also
nesting in the'
Conifer species
too.

18. Live Cottonwood 31 cm DBH Nettle, Rasp- the decline in
Balsam Poplar 28.3 cm DBH. berry, Bedstraw numbers in this
(2) sedge, Jewel- colony is prob-
Tree height: 18-20 m weed, Choke ably due to
Cherry, May several of the
flower, and large nest
Sweet Cicely. trees being
A border of broken in a
Cedar Balsam storm. This
and Alder has produced
surrounds the a few openings
point and the in the wooded
nest tree area. canopy of 30-40
M2.

19. Ash 22.8 cm.DBH (2) Red Osier Dog- This is a
Balsam Poplar 25.1 cm DBH wood, Sand Bar classic example
Tree height: 12-16 m Willow, Jewel- of the shift
weed and bare from one
Sand-muck. colonial
See map in species (Ring-
this report. billed Gulls)
which are
declining as
the Great Blue
Herons are
increasing with
the successiori
to trees.

19. Continue However, this
dredge mate-
rial island
which is
subject to much
wash by passing
ship traffic is
rapidly washing
away and is
only 20-30 m'
wide. How long
this colony
will exist
depends on the
speed of
erosion of
the island.
Beavers have
cut down some.
trees at this
site too.

20. One dead Elm 78.2 cm DBH Red Osier Dog- It is only a
holds 27 of 44 nests. wood, Nettle & matter of time
Live Elm 35.5 cm DBH has Jewelweed. See until the two
14 of 44 nests. map in this main nest trees
2 Ash and I White Birch report. fall and cause
hold other nests, a few years of
25 cm DBH decline until
Tree height: 14-18.5 m the other trees
grow larger. No
threats are
seen to this
colony other
than tree loss.

21. 12 of 22 nests in Dead Cow Parsnip The only threat
Elm 60.4 cm DBH Red Ostier to this colony
4 of 22 nests in Live Dogwood, Nettle is loss of
Elm 26.1 cm DBH and Jewelweed. trees.
3 more in Live Birch See map in this
20 cm DBH report.
3 more in smaller Live
E 1M
Tree height: 12-16 m

22. Red Oak 36.8 cm DBH (4) June berry, The proximity
A few Birch 22 cm DBH Choke Cherry, of this island
Tree height: 16.5 m Thimble berry, to Bay Mills
Red Elder, tribal resi-
Ground Hemlock, dences and
Striped Maple, fishing docks
Soloman's Seal, as well as the
Cow Parsnip, fact that
and Bane berry. fishing boats
frequently seek
lee moorings at
the island make
it possible to
be disturbed
unduly.
However, the
colony seemed
veryvigorous
this season.

23. Live and Dead Aspen See photo Summer home in
Tree height: 12 m showing prox- proximity of
imity of the colony maybe
cabin in this responsible for
report. the drop in
numbers here.
Further devel-
opment of
residences will
probably cause
more damage to
the herons.
24. White pine 45.2 cm DBH Bear berry, Two groups of
Tree height: 15-17 m June berry, nests (as many
Choke Cherry, as 6 per tree)
Dwarfed Balsam, 18 on west
and bare gran- colony and 3 on
ite rock. east of Middle
Island. 4 more
nests are on
Eastern smaller
island. The
undisturbed
quality of this
colony seems
assured by the
status as a
National
Wildlife
Refuge.

25. White Birch (many dead) Spinulose tree Herons have
30.5-35.5 cm DBH fern, Mountain lost much
Quaking Aspen 25-30 cm DBH Maple, Mountain habitat at the
Red Maple Ash, Red Elder, southwest point
Tree height: 12-16 m Canada Yew, where Cormor-
Raspberry, ants have taken
Currant, Pin over, but the
Cherry. herons have
responded by
moving North-
easterly and
splitting into
at least 3 sub-
colonies. Many
former heron
nest trees have
blown down near
the south-
central portion
of the island,
still the col-
ony continues
to increase.
The line for
the Environ-
mental Area
shown of the
DNR map should
be re-drawn.
A recent
campsite was
located near
the central
part of the
heron colony
along the
shore.

26. Quaking Aspen 40.3 cm DBH Much ground Many trees
Yellow Birch 44 cm DBH dead; some blown down.
White Birch 35 cm DBH bare ground, This is prob-
Tree height: 15-17 m large patches ably what
of Hounds caused this
Tongue, Wood colony to move
Nettle, and to the north-
Yellow Rocket west quarter of
Some Columbine the island. The
and Chickweed, understory
Violets, moss, shows much
and Jack-in- stress from
the-pulpit. whitewash which
is probably
killing trees
too. Fishing
pressure is
very high in
this area. Even
though it is
State Park
land, I have
found Terns
shot here
before, and
presumably
that could
happen with
herons also.

27. Dead White Birch Red Elder, As long as this
Live Quaking Aspen Raspberry, island stays in
Tree height: 16-18 m Canada Yew, an undeveloped
Jewelweed, state the con-
and border of tinuance of the
Cedars between herons seems
the edge of the assured. They
colony and the have already
cobble shore. moved from the
East end in
1976 because
some of the
woods either
burned or were
blown down.

28. 4 Birch 30 cm DBH Toothwort, The herons are
contain 7 nests Columbine, assured safety
Tree height: 10-12-m Cow Parsnips, by the owners,
Choke Cherry, Nature.Conser-
Red Osier Dog- vancy, who have
wood, Red El- restricted
derberry. access to the
island. The
only threat
would be the
loss of nest
trees.

29. Large Choke Cherry, Bare sand and The take over
Elm, Ash; less than stone, some of nest trees
30 cm DBH Burdock and by 127 Double-,
Tree height: 6-10 m Cow Parsnip Crested Cor-
morants has
probably
discouraged the
herons and
killed many
nest trees.-
The biggest
threat here,is
high water and
waves that wash
over this
island
occasionally.

30. Quaking Aspen 26.9 cm DBH Red Elder, I see no threat
(4) Jewelweed, to these herons
White Birch 23.4 cm DBH (3) Canada Yew, as long as
Tree height: 12-15 m Balsam Fir. development by
See photos in humans is
this report. avoided.

31. White Birch Limestone rock The rocky
Quaking Aspen Shelf substrate nature of this
See photo in island seems to
this report. preclude future
development.
Colony is
separated into
13 nests on
East &"8 on
West.

32. White Birch - ---------- This colony has
Quaking Aspen no known threat
to it.

33. White Birch (a few dead) Rich ground This large
25.7 cm DBH (3) cover, Spinu- island seems
Tree height: 12-16 m lose Wood safe large
fern, Red numbers of
Elder, Smart- Canadian Geese
weed, Squirrel live in inter-
corn, White ior, and a
Cedar, Black campsite was
Spruce. Photo noted there.
in this report.

34. Cottonwood 38.1 cm DBH Some sand, No threats
Tree height: 16 m wet-marshy. known.
See map in
this report.

35. Dead White Birch 27 cm DBH Large clear The chief'
Dead White Cedar - area with threat to this
Tree height: 8.3-11.6 m blown down heronry is the
White Cedar. dead and dying
Cow Parsnip, trees which
Nettles, Jewel- seem to blow
weed, Canada. down very
Thistle. See easily in the
photo in this shallow soil.
report.

TABLE 5

KEY TO 8X10 BLACK AND WHITE PHOTOGRAPHS

COLONY NAME DATE OF EHOTOS AND (NUMBER)

1.
2. Dickinson Is. 18 April, 1987 (2)
3. Hesterman Is. 18 April, 1987 (2)
4. L. Charity Is. 18 April, 1987
5. ------ ------
6. Scare Crow 02 May, 1987; 06 June, 1987
7. Gull Is. 02 May, 1987 (2); 06 June, 1987
8. ------ ------
9. ------ ------
10. Goose Is. 10 June, 1987
11. ------ -------
12. ------ ------
13. ------ ------
14. ------ ------
15. Cedar Is. 16 May, 1987
16. Round Is. 16 May, 1987
17. Love Is. 16 May, 1987
18. Roach Pt. 16 May, 1987
19. Moon Is. 16 May, 1987
20. Gem Is. 30 May, 1987 (2)
21. Rock Is. 30 May, 1987
22. Bay Mills Is. 30 May, 1987
23. Williams Island 03 July, 1987
24. Huron Is. 30 May, 1987
25. Traverse Is. 24 May, 1987
26. ------ ------
27. St. Helena Is. 01 May, 1987
28. Hat Is. .01 May, 1987
29. ------ ------
30. Squaw Is. 01 May, 1987 (2); 10 June, 1987
31. Epoufette Is. 24 May, 1987
32. L. Hog Is. 24 May, 1987
33. Big Gull Is. 24 May, 1987
34. ------ ------
35. Round Is. 24 May, 1987

*23 2 2---- 21
0 - 0 9
3231 1
00 80 0

9
0 8
33

7
6 5

Fig. 1. Coastal Great Lakes Great Blue Heron Colonies - Michigan 1987

20 M

@ALPENA, Mi. 8 KM

DENSE HERRING
,,GULL NESTS

-EAQ@-CROWNED NIGHT'
HERO C, (k f-:
SMALL A H C -
GREAT SWE SH
HERONSIN
SH TREES
OPEN NETTLE AREA

HERB AND HRUB COBBLE BEACH

HERRING GULLS NESTS DISPERSED OVER ISLAND

GULLISLAND-7

200M

ST MARTIN ISLAND

38 6RZA'r isLus k Eju
LIVE A@W DEAO -519C

ST MARTIN ISLAND - 9

40ONE TO
MARQUETTE ISL7A/
3km OPEN BEACH

DECIDUOUS VEGETATION

WHITE CEDAR

PONDSjFLOODED AREAS

I BCNH NEST

7?9 HG NESTS DISPERSED OVER ISLAND

913CHN NES

B7 GBH NESTS

1&84 ho -TOTAL AREA

loom

CORMORA"rS Jt4 -nWCS

GOOSEISLAND

45* N E TO BEAR ISLAND
2600 SW TO STRONGS ISLAND /!!
1400m 550m
N

53 ho - Ix
WOODEN GRAVEL BEACH
DOCK lom

0 G BH NEST TREES (3 NE
COAST GUARD TOWER 241 HG NESTS71)I$
DENSEIY ENTIRE ISLAND
WOODED

CLEARING

U.S. CADASTRAL
SUR'&Y. MARKER

CROW -ISLAND

00 DUE NORTH TO MAINLAND

2W N E TO LITTLE SADDLEBAG
ISLAND 12 00 m

CABIN WOODY
VEGETATION

CLEARING

L64 ha -TOTAL AREA

ROCKY 20M
BEACH

3M HS NESTS DISPERSED OVER ISLAND

32 GSH NESTS

HERONRY

SADDLEBAG ISLAND - 12-

I0*NE TO DRUMMOND- ISLAND
2 km

2700 DUE WEST TO
WEST SHORE HURON BAY,
I km

000 N
0 275 ho TOTAL AREA

25M

DENSELY
WOODED

G 8 H NEST TREES (2.z fasrs)

0 1 HG NEST

ROCKY AREA DEVEAD OF VEGETATION

A
GRAVEL ISLAND - 13

1.38 ho -TOTAL AREA

20m

400@ N E TO HAY POINT
2.2 km

,,--COAST GUARD LIGHT

ABANDONED LIGHT HOUSE

GREAT BLUE HERON
COLONY
23 NESTS

DENSELY
WOODED

1300 S E TO LIME IS ND\\
1. km

ROUND ISLAND -
LA
6

3250 NW TO KEMPS POINT.
1800M N

COAST GUARD LIGHT .61 ha - HG COLONY

200m

HERRING GULL COL Y AREA ENLARGED BELOW
IS NESTS WIDELY SC TTERED RING-BILLED GULL COLONY
AMD G KILAT bLfJrr- qF a

WILLOW N
56 ho - RBG COLONY
Im BLUFF
lom

DEVOID OF ASPEN ETTLES11 ASPEN
VEGETATION +
A O.5-I.Om CLAY BLUFF
"NETTLES"

ASPEN
ELDER PHRAGMITES

ELDER

1.0-1.5m CLAY BLUFF

OTHER WOODY AND
HERBACEOUS VEGETATION

MOON ISLAND - 19
ON
A r@ERED

72 ho -TOTAL AREA

lom

0
WOODED

DENSE CLEARING
SHRUBS

220 s W TO
WHIPPLE POINT
1400M 0

o AM. ELM GBH NEST TREES (44 NESTS)
0 WHITE BIRCH

27 HG NESTS DISPERSED OVER ENTIRE ISLAND

GEM.ISLAND-20

35-

.31 ho -TOTAL AREA

lom
/
400 N E TO PUMPKIN
POINT, 1600m

FJ NS
SHRUBS 0
2TOODUE WEST SHRUBS
TO SUGAR ISLAND CID W
soom

0 AM. ELM - GOH NEST TREE 42. NESTS)

B BRAMBLES

NS NIGHTSHADE

CP COW PARSNIP
N NETTLES

WR WILD RYE

BOULDER RIDGE
INTIL. BOUNDARY COMM. MARKER

53 HO NESTS DISPERSED OVER ENTIRE ISLAND

ROCK ISLAND-23
4(
P(

HERRING GULLS
CD

ool
/7 GREAT BLU
HERON NESIS

NO HERRING
GULLS

Q30

HiFFRING 0 Q
GULLS r,
lo-r

NO HERRING GULLS

SCALE I MM a 1.5 M

TREES AND
SHRUBS
SHORELINE
Ll.@ rit-
CONTOUR LINES1
HERRING
GULLS
----NESTING AREA
(HERRING GULLS)
dl

EDGE OF GROUND
% VEGETATION

,HAT ISLAND-248 CASPIAN TERNS

-37

SCALE I M
C,% TREES

SHORE

--4- CONID

ESTI
---N
Rl MG

%Aj

4 GREAT BLUE HERON NESTS

SCALE I MIV )D M
WEST GRAPE ISLAND-7-9

DIRT
RIDGE
GRAVEL GRAVEL

DOGWOODo NETTLES,
GRASS
14'rLROIV AIF-Sr
TREES AND SHRUBS
DENSE GROUND HEMLOCK

GRAVEL BEACH
2600
2200m TO ST DIRT
MARTIN ISLAND
COBBLE ROCK

30m P
A-

ROCK, COBBLE BEACH
HG NESTEDAROUND ENTIRE ISLAND,SOME SHORELINE RIDGE
CONCENTRATIONS ON THE NORTH TIP, SOUTH,
AND WEST SIDES.
TOTAL AREA ABOUT, 5.47 ho
VISITED 7-2-76
1000- 1230 HRS.

GULL ISLAND -33

SANDY POINT, DOGWOOD, SANDY BEACH
NETTLES,HG
LOW AREA )NITH STANDI

ASPEN, BIRCH,
BRUSH 0 HG N
WlLLOW, ASPEN THE NO
\240

I
LEDGE

BLACK-cRoWNED
NK3HT HERONS )MLLDWS SAN
ASPEN@ELM SMALL STAND CAT
200

ILLOWS
FLOODED W
SOIL SAMPLES:
Of GREAT BLUE HERON COLIONY
D
GREAT BLUE HERLW COWNY
ST. VITAL ISLAND -3+

N STONE COBBLE BEACH

HG COLONY

Vol SHALLOW POOLS OF WATER

GROUND
WHITE BIRCH GBH COLONY
WHITE CEDAR

RBG COLONY
(.99ha.)

TOTAL AREA(EST)-9ho
LOCATED: 45045-8'6046'

ROUND ISLAND - 35

IIMINIIIIIIIIIIIIIII
3 6668 14104 8415 _