Portage Island National Wildlife Area Management Plan: chapter 2

2 Ecological resources

2.1 Terrestrial and aquatic habitats

Portage Island is a coastal sand dune ecosystem with alternating dune ridges and slacks running in a northeast to southwest direction along its length. The island is minimally disturbed by human activity. The tops of the dunes exhibit a well-defined succession from predominantly Marram Grass (Ammophila breviligulata) to shrub dune, lichen and shrub forest. Salt marshes are found predominantly adjacent to Gammon Cove and in dune slacks along the east side of the island, while brackish and freshwater marshes and swamps occupy the interior slacks. According to local historical knowledge, the Jack Pine (Pinus banksiana) forest covering the northern half of the island (Figures 4 and 5) has burned twice in recent years; the last large fire occurred in the late 1940s ( Malone 1978 ). To date, 51 plant species have been documented on Portage Island ( Malone 1978; Christie 1978; Hinds 1983; Hinds 2000; Roland 1998 ).

The island’s flora is dictated largely by the age of the underlying dunes. Shrub swamp dominated by Meadow-Sweet (Spiraea latifolia), Sweet Gale (Myrica gale), Blue-Joint (Calamagrostis neglecta), Water Parsnip (Sium suave) and Wire Birch (Betula populifolia) are common in the interior portions of Portage Island. Broad-leaved Cat-tail (Typha latifolia) and Saltmarsh Bulrush (Bolboschoenus maritimus) are also common. The majority of the interior shallow water ponds are influenced by marine waters and airborne salt, resulting in a dense growth of Widgeon Grass (Ruppia maritima) within them. Ponds in coastal salt marshes are often fringed by Salt-water Cord Grass (Spartina alterniflora) and hold some Widgeon Grass. Eelgrass (Zostera marina) is dominant in the large pond at the south end of Portage Island. Sago Pondweed (Potamageton pectinatus) and the uncommon Sparganium multipedunculatum are present in the large pond on the east side of the island ( Whitman 1970; Rothfels and Blaney 2004 ).

The salt marsh flora is consistent with other marshes of the region ( Hanson 2004 ). Dominant species such as Salt-meadow Grass (Spartina patens)and Black Grass (Juncus gerardii)occur throughout, and Broad-leaved Cattail, Red Fescue (Festuca rubra), Bog Rush (Juncus balticus) and Scaly Sedge (Carex palacea) occur on higher ground. Some patches of Seashore Saltgrass (Distichlis spicata) exist. Scotch lovage (Ligusticum scothicum) is common on areas enriched by wrack. Samphire (Salicornia europaea), Orache (Atriplex patula) and Sea-Milkwort (Glaux maritima) are also well represented in the National Wildlife Area (NWA).

Beaches surround the island, and except for occasional clumps of Beachgrass or Sea Lyme-grass (Elymus mollis), the beaches are devoid of vegetation. Areas of upper beach reaching inland to the east, caused by storm erosion, are becoming colonized by Sheep Sorrel (Rumex acetosella). Sea Lyme-grass and Beachgrass, the dune pioneering species, have stabilized the relatively new land on the south end. This widespread “Ammophila dune” offers protection for the establishment of such common species as Sea-beach Sedge (Carex silecia), Wild Rose (Rosa virginiana), Beach-pea (Lathyrus japonicus) and Bayberry (Myrica pennsylvanica).

2.2 Wildlife species

The unique coastal habitat of Portage Island NWA has greatly influenced wildlife species composition and abundance on the island. The mosaic of undulating dunes in different phases of plant succession, combined with interspersed wetlands, provides a diversity not seen on adjacent coastal islands.

2.2.1 Birds

The location of Portage Island NWA in the middle of the mouth of the Miramichi River results in substantial numbers of birds on and around this island. Although there are no large colonies of seabirds or other colonial waterbirds on Portage Island, the area is used extensively as a feeding and loafing site by a number of species. The forested portion of the island also hosts a large number of passerine species. To date, 77 species of birds have been observed on and around Portage Island NWA.

Double-crested Cormorants (Phalacrocorax auritus) and Common Terns (Sterna hirundo) feed in the shallow waters around the island and rest on its beaches, with maximum counts of 595 and 521 birds, respectively. Egg Island, just south of Portage Island, supports a colony of up to 610 pairs of Great Black-backed Gulls (Larus marinus), 441 pairs of Herring Gulls (Larus argentatus) and 558 pairs of Double-crested Cormorants ( MacKinnon 1996 ). Birds from these colonies undoubtedly frequent Portage Island.

Immediately north of Portage Island is Neguac Bar, a site that once supported a large Common Tern colony. Another Common Tern colony is present at “Little Huckleberry Island” approximately 10.5 km south of Portage Island NWA. In the late 1980s and early 1990s, these two colonies supported upwards of 1800 and 3500 Common Terns, respectively. However, due to human disturbance and the erosion of suitable nesting areas, they have decreased substantially in recent years. Portage Island holds the potential to provide alternative nesting sites free of the human disturbances that have negatively impacted these colonies. Large colonial nesters such as Great Blue Heron may, on occasion, relocate to suitable habitat near an existing colony or to nearby islands ( Davis et al. 2011; MacKinnon et al. 2005; MacKinnon and Kennedy 2006 ).

Gulls rest and forage along the shore of Portage Island. Peak numbers of 23 Bonaparte’s Gulls (Larus philadelphia), 200 Ring-billed Gulls (Larus delawarensis), 465 Herring Gulls and 175 Great Black-backed Gulls have been recorded at the NWA.

The salt marsh ponds and inter-dune slacks also support several bird species. American Black Duck (Anas rubripes) is the most commonly observed and abundant species of waterfowl; however, lesser numbers of Green-winged Teal (Anas crecca), Mallard (Anas platyrhynchos), Blue-winged Teal (Anas discors), Northern Pintail (Anas acuta) and American Wigeon (Anas americana) have been recorded. Great Blue Herons (Ardea herodias) also frequent these ponds. Red-breasted Mergansers (Mergus serrator) have been observed in substantial numbers, with a peak of 333 recorded ( Christie 1978; Erskine 1978 ).

Shorebirds use the intertidal flats around the island, especially along the north and west side, making extensive use of Gammon Cove. Although surveys have been infrequent, 11 species of shorebirds have been observed. Nine of these are common migrants; 3 species, Willet (Tringa semipalmata), Spotted Sandpiper (Actitis macularia) and Common Snipe (Gallinago gallinago)

probably breed on the island. Black-bellied Plover (Pluvialis squatarola) is particularly abundant on the beaches of Portage Island NWA during spring migration.

One of the more obvious bird species nesting on Portage Island is Osprey. At least three nests were observed in 2000, and four active nests were observed in both 1987 and 1989. The forested portion of the island also supports a number of passerine species, although extensive surveys have not been conducted.

The endangered Piping Plover (Charadrius melodus) nests on Portage Island, preferring the exposed dunes and blown-out areas around the southern end of the island.

2.2.2 Mammals

Mammal diversity on Portage Island is low. The following species have been observed in the NWA: Meadow Vole (Microtus pennsylvanicus), Masked Shrew (Sorex cinereus), Snowshoe Hare (Lepus americanus), Mink (Mustela vison), Red Fox (Vulpes vulpes) and Grey Seal (Halichoerus grypus).

Walrus (Odobenus rosmarus) were once hunted on Portage Island. In 1968, R. D. Young collected a centuries-old walrus skull from the island. This specimen (NBMG 4584) is with the New Brunswick Museum ( Miller 1990 ).

2.2.3 Reptiles and amphibians

No reptile or amphibian species have been recorded on the NWA.

2.2.4 Fish

The salt marsh ponds and inter-dune slacks support stickleback and other brackish water fish, as inferred by the frequent sightings of foraging Great Blue Herons and Belted Kingfishers (Ceryle alcyon). However, these wetlands have not been sampled to determine species composition.

The beaches of Portage Island NWA frequently attract large numbers of birds that feed on spawning Sand Lance (Ammodytes americanus). On June 19, 1985, 173 Common Terns, 50 Greater Black-backed Gulls, 250 Herring Gulls and 50 Ring-billed Gulls were observed foraging for this fish along the southeast side of Portage Island.

2.2.5 Insects

A brief survey of conspicuous macroinvertebrates was recorded by the Atlantic Canada Conservation Centre ( Rothfels and Blaney 2004 ). These observations included three species of beetles, six species of butterfly and seven species of dragonfly, as well as an additional dragonfly specimen identified at the genus level only. One beetle, Trichodes nuttalli, associated with pine stands and sand prairie, is the first record for New Brunswick.

2.3 Species at risk

The endangered Piping Plover (melodus subspecies) has been recorded breeding on Portage Island for many years (Table 4; Figure 6). Portage Island supports upwards of 1% of the roughly 400 individuals in the Atlantic provinces ( Environment Canada 2012 ).

Portage Island NWA provides habitat for Piping Plover for breeding and possibly staging. This species prefers wide sand, gravel or cobble beaches as nesting sites; barrier islands, sand spits and peninsulas are preferred locations. The area of beach considered suitable for nesting, feeding and cover includes the intertidal zone from the low water mark up to the crest of the vegetated dune, typically identified by the presence of Marram Grass or other dune vegetation. Habitat for feeding and brood-rearing must be located in close proximity to nesting sites. Microhabitat features such as the presence of wrack, driftwood and ephemeral pools enhance habitat quality by providing feeding opportunities and shelter. The entire beach area is therefore an important component of critical habitat, from the low water mark and the intertidal zone up to the line of Marram Grass or other vegetation, or the peak of the vegetated dune ( Gratto-Trevor and Abbott 2011 ). Critical habitat has been identified for Piping Plover on Portage Island ( Environment Canada 2012 ).

No other species at risk are known to breed in the NWA, although the Peregrine Falcon (Falco peregrinus) is a spring and fall transient. Other bird species of interest, identified as either sensitive or at-risk by the Province of New Brunswick, are Black-crowned Night Heron (Nycticorax nycticorax), Brown Thrasher (Toxostoma rufum), Horned Lark (Eremophila alpestris) and Willet (Catoptrophorus semipalmatus).