Harbor Island is located at latitude 46 degrees 03' and longitude 083 degrees 46' in Potagannissing Bay north of Drummond Island, Chippewa County, Michigan. With approximately 300 ha (750 A) of land mass it is the largest of some 50+ islands in the bay, and as such is a significant reservoir for wildlife in the area (it is the only island known to support a deer population throughout the winter) and is most representative of the habitats indigenous to the islands in this region of the U.S. Great Lakes. Harbor Island supports the major regional habitat types mixed upland forest (oak-maple), mid-seral stage forest (aspen-ash-birch), boreal forest (cedar-balsam fir), old field (grass-herb) and marsh (rush-pondweed). Excluded on Harbor Island are the sand beaches and low dunes found on the north shores of Lake Huron along Michigan's upper peninsula. Having the highest elevation (680' above sea level) of all the islands in the bay, Harbor Island supports the greatest growths of deciduous species such as oak and maple, thus providing another niche, exploitable by both breeding and migrating avian species, not available on many of the smaller adjacent islands.Harbor Island almost completely landlocked the 60 ha (150 A) harbor which so appropriately is the island's namesake. The unique harbor is relatively immune from winds, except when out of a couple of degrees SSW. The marshy shoreline of the harbor provides nesting habitat for the Pied-billed Grebe, American Bittern, Black Tern, Long-billed Marsh Wren and Red-winged Blackbird and rearing habitat for broods of Mallards, Black Ducks, Wood Ducks, Common Goldeneyes, and Red-breasted Mergansers. The sheltered harbor and calm waters are important as a refuge and feeding ground for the waders (e.g. herons) and the Ospreys, which need shallow water and clear visibility for fishing. Four Great Blue Heron colonies are located within 18 km of the island. Thus the harbor is within foraging distances for some 242 herons, from U.S. waters alone (1977 data -see W.C. Scharf, M.L. Chaiviberlin & G.W. Shugart. 1978. Colonial Birds Nesting On Man-made And Natural Sites In The U.S. Great Lakes. U.S. Army Engineers Waterways Experiment Station. Vicksburg, Miss.). The significance of this uniquely protected marsh is greater due to the fact that all of the adjacent islands within a two-mile radius have rocky and deep shorelines essentially devoid of marsh vegetation. The east shore of the bay along Drummond lsland is also marshy however here the presence of resort complexes and fishermen is a continual source of disturbance and recreational and residential development is increasing. Currently all of the adjacent islands are privately owned. Many have a summer residence on them or, given the current trend, in all probability soon will. The significance of Harbor Island as a reserve of the flora (1, 23 species) and fauna (146 species) indigenous to this region will of course take on an ever increasing significance as the other islands are developed.Bald Eagles, Osprey and Great Blue Herons have traditionally nested in the bay. Harbor Island offers suitable habitat for these breeding species. Mrs. Ken Payment of Drummond located a large raptor nest "two years ago" which she believed to be an eagle's nest (although it was more likely an Osprey nest). We were unable to relocate the nest during either our ground searches or an aerial search by helicopter. The continuous presence of Black-crowned Night Herons on the island for the past several summers suggests a possible northern extension of this species' breeding range. Colonization by this species may well occur in the region within the near future and the Harbor Island habitat would be a very likely location. If this occurs it will become the northernmost Black-crowned Night Heron colony in the U.S. Great Lakes. Goose Island, Mackinaw County, Michigan (latitude 45 degrees 45') is currently the northernmost colony (Scharf, Chamberlin & Shugart 1978).Harbor Island, and the entirety of Potagannissing Bay, is an important stop-over for migrating waterfowl, hawks, shorebirds and passerines traveling in a southeasterly or northwesterly direction. During migration White-winged Scoters, even Surf Scoters, Bald Eagles, Whimbrels, Greater Yellowlegs, Short-billed Dowitchers, Ruddy Turnstones, Dunlins, Sanderlings, White-rumped Sandpipers, Least Sandpipers, Semi-palmated Sandpipers, Bonaparte's Gulls and 17 species of the northern warblers have been observed to utilize the area.The island is botanically and zoologically rich. Of special botanical value are the orchids, gentians and lobelias. The daily utilization of the island's habitats by Osprey, Harriers and Cooper's Hawks (all on Michigan's threatened species list) and the recurring presence of Michigan's largest carnivores (coyote, red fox, black bear, bobcat, lynx -the latter three observed by Benua) are of ecological importance to the maintenance of a healthy, complex food web in the region. The accompanying species lists speak for themselves.
The following species list was compiled from observations during intensive ground searches throughout the island's habitats and from banding operations conducted during 1-3 and 10-13 September 1978. Four standard 1, 2-foot, 4-panel nylon mist nets were set on the island (locations are given on the map). A total of 51 inpiduals of 26 species were banded. Also included in the inventory are species observed on the island by Chamberlin during annual spring/summer visits from 1972-78. During 1976-77 the island was visited by Chamberlin as part of a colonial bird survey of the U.S. Great Lakes (Scharf, Chamberlin & Shugart 1978). Additional observations during 1965-78 made by Louis Benua, seasonal resident on adjacent Bald Island, have also been incorporated. This inventory sets Harbor Island's avifauna at a minimum of 123 species.B- Known Breederb- Probable BreederP- Potential BreederM - MigrantX - Status Uncertain* On Michigan Threatened Species List** On U.S. Endangered Species List+ Being considered for Michigan & U.S. Endangered Species Lists1- Observed 1-3 & 10-13 Sept. 19782- Observed by Chamberlin 1972-783- Observed by Benua 1965-78
Searches of the various vegetational habitats of Harbor Island were conducted on 1-3 September and 10-13 September, 1978 during which the following list of plant species was identified. It is likely that spring-flowering species were missed because they are inconspicuous at that time of year. In most cases the taxonomy of the plant species refers to Helen V. Smith, Michigan Wildflowers , 1961, Cranbrook Inst. Sci., Bloomfield Hills, Mich. 465 p. for herbaceous terrestrial species; N. C. Fassett, A Manual of Aquatic Plants , 1957, University of Wisconsin Press, Madison, 405 p. for aquatic species; C. Billington, Ferns of Michigan , C~anbrook Inst-. Sci., Bloomfield Hills, Mich. 240p. for ferns; C. Billington, Shrubs of Michigan,1949 Cranbrook Inst. Sci.,Bloornfield Hills, Mich., 339p.for shrubs;.and C. H. Otis, Michigan Trees , 1913, Univ. Mich. Press, Ann Arbor, 362p. for trees.
* protected species
Eleven snap trapping lines (see map) were made of
varying lengths for 5 nights (1,2 and 10,11,1, 2 September, 1978) in varying
habitats for a total of 362 trap nights. Traps were spaced at 14 yard intervals
according to the method described by R. L. Smith, Ecology and Field Biology,
1966, Harper and Row, New York, p. 653, and 66 traps sampled 1 acre. There were
34 Peromyscus maniculatus gracilis trapped and one Clethrionomys gapperi.
Estimates of 6.5 Peromyscus per acre reveal a very high population of this
species. This is especially surprising, because trapping conditions were
sub-optimum due to heavy rain and wind each night we trapped.
Other inclusions on the mammal list come from the
observations of tracks, scats, and capture of bats in mist nets. Some of the
mammals are noted to be from the list of Mr. Louis Benua, Colombus Ohio from
adjacent Bald Island.
All appropriate hiding places and marshes were
searched, and the following species were found on Harbor Island.
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An X marks the back of this tiny treefrog. Although small in size spring peepers have a surprisingly loud peeping call commonly heard in the spring.