Nova Scotia Environments for Birds

This large area of land and water encompasses a great deal of geological and ecological diversity. The reader may find extensive information on the physiography and geology of the province in a monograph by Roland (1983) and also in a two volume survey of the natural history of the province prepared by Simons et al. (1984). A good summary of climate and weather in Nova Scotia is in Gates (1975). Here, only a brief discussion of environmental characteristics is made in the context of the birds that occur in the province. All significant place names and coastal areas in this section of the Introduction are shown on the regional map on pages 466-7.

The geographical setting of Nova Scotia has important effects on its birdlife. The province is virtually insular, thrusting out into the North Atlantic about halfway between the equator and the North Pole. Islands and peninsulas characteristically have a less diverse birdlife than is found on nearby mainlands (Macarthur and Wilson 1967). It is noteworthy that some birds nesting in Maine, southern Quebec and even nearby New Brunswick do not nest in Nova Scotia or do so rarely. However, the province is well situated to receive transient and vagrant birds from other parts of North America, offering a last landfall for birds coming from the west and a first landfall for birds migrating or displaced over the sea.

The weather in Nova Scotia is related to its geographical setting and influences its birdlife. The mean boundary between the tropical and arctic air masses passes northward in May and southward in September across the province. Airflow from much of the continent focuses on Nova Scotia; mean wind directions are southwesterly between spring and fall and more westerly in winter. Storm tracks from the southeastern and midwestern United States also converge on Nova Scotia, creating greatly variable weather conditions and frequent high winds. This convergence of windstreams on Nova Scotia has obvious consequences for migration and vagrancy of birds (see McLaren 1981b).

No part of the province is more than about 70 km from salt water, a considerable moderating influence on the climate. Thus average daily maximal and minimal temperatures at Halifax are about 0.5 and -6.6ēC in January and 22.7 and 13.8ēC in July. In comparison, temperatures at Kingston, Ontario, at almost exactly the latitude of Halifax, are more extreme: -3.6 and -12.3ēC in January and 25.7 and 15.5ēC in July. There is a temperature gradient within the province from Cape Breton Island to Yarmouth County, the latter averaging about 2ēC warmer than the former in January, but the two differing little in July. There is also an offshore-inland gradient in temperature: Sable Island averages almost 2.5ēC warmer and Kentville, in the sheltered Annapolis Valley, averages 2ēC cooler than Halifax in January; Sable Island is about 2.7ēC cooler and Kentville about 1.0ēC warmer than Halifax in July. These differences affect birdlife. Spring comes late and breeding seasons are delayed in Nova Scotia, especially in coastal areas, compared with regions well inland in eastern Canada. Autumn migration is relatively protracted in Nova Scotia, and many half-hardy birds linger into late fall or early winter compared with other places in eastern Canada. Within the province such late birds are more likely to be found in Atlantic coastal regions than in inland localities or along the Bay of Funds and Northumberland Strait.

Because it lies on so many storm tracks, Nova Scotia is rather wet. An annual average of 1100-1600 mm of precipitation spread rather evenly through the year is collected at most recording stations; this compares with about 870 mm at Kingston, Ontario. The proportion of this precipitation that appears as snow is greater inland and further northeast in the province about 9 percent on Sable Island, 17 percent at Halifax, 21 percent at Kentville and 21 percent in Cape Breton Highlands National Park. During some winters on the Eastern and Southwestern shores, very little snow stays on the ground, and seed-eating birds may thrive. During winters with heavy snowfalls, many more of these birds depend on bird feeders. Nearly all the province has cloudiness over 60 percent of the year; about 75 percent occurs on eastern Cape Breton Island. Coastal fog, especially along the Atlantic and Fundy shores, prevails from April through July. Even inland, the amount of bright sunshine is limited: at Greenwood, Kings County, it is about 25 percent in January and 50 percent in July. In some years, rain, fog, and low temperatures may considerably reduce the reproductive success of birds that feed their nestlings on insects.

The geological history of Nova Scotia has shaped some aspects of present-day bird distributions in the province. Nova Scotia is part of the Appalachian Region of eastern North America, in a section where the land has been exposed to subaerial erosion since the Carboniferous period, some 280 million years ago. An uplift of the much levelled landscape during the early Tertiary period led to some 50 million years of levelling and dissection of river valleys, accelerated during the Pleistocene epoch, with its succession of ice sheets. The present landscape is a result of deep erosion of the softer rocks of the old landscape. Hardrock areas have remained as hills and plateaus: the Cobequid and North mountains in central and south Nova Scotia, small areas in Pictou and Antigonish counties and in southern Cape Breton Island, and the extensive Cape Breton Highlands in the northeast. The maximum mainland elevation is Mount Nuttby in the Cobequids at 360 m, but the maximum overall is North Barren in Cape Breton Highlands National Park at 530 m. This relief is modest by world standards—there are no alpine birds in Nova Scotia and no arctic or subarctic species lingering to nest on our hilltops, such as found in Newfoundland, southeastern Quebec and even New England (e.g.,Water Pipits on Mount Washington). The ornithological significance of our hills is that they offer relatively inaccessible areas where shyer birds, such as raptors, may nest undisturbed.

Hardrock areas along the coast, particularly on the Eastern Shore and on Cape Breton Island, offer considerable opportunities for cliff-nesting or islet-nesting species. In such areas, cormorants and eiders breed in some numbers, and our only colonies of such birds as Black-legged Kittiwakes are to be found.

An important consequence of glaciation is the extensive deposits of till, forming large eskers and drumlins in many areas and supplying materials for redistribution by rivers and coastal currents. The sea level continues to rise relative to the rebound of the land unburdened of its Pleistocene ice, and parts of the coast are characterized by drowned estuaries with extensive salt marshes and often by unstable sandbars and dune beaches. These "softer" coastal landscapes, particularly along the Southwestern Shore, the inner Fundy Shore, and the Northumberland Strait offer many opportunities for marsh birds, shorebirds and waterfowl. On the Bay of Fundy side, the massive tides and greater rates of erosion have produced extensive salt marshes and mudflats in the Minas and Cumberland basins. These areas are major stopovers for migrating shorebirds, particularly Semipalmated Sandpipers, in eastern North America. At places where the lowlands meet the sea, particularly in the Minas and Cumberland basins, dykes were built by the French settlers, beginning in 1632. In time, former mudflats and salt marshes have become rich meadows which today attract open-country birds, particularly raptors in winter. In recent years, the creation of freshwater impoundments in former salt marshes has produced valuable habitat for marsh birds and waterfowl.

In general, however, the characteristics of birdlife in Nova Scotia are determined by the plant cover rather than geological circumstances. The province is largely forested and lies within the Acadian Forest Region (Rowe 1972). This region is transitional in nature, although the Red Spruce generally is confined to it. Thus many different plant associations occur in the forests, which may be purely coniferous, purely broad-leaved or various admixtures.

A narrow belt of largely coniferous forest extending 5–25 km inland along the Atlantic coast is characterized by poor growths of Balsam Fir and White and Black Spruce, with some Red Maple and birches. Characteristic birds in these forests include the Gray Jay, Boreal Chickadee and rarely Spruce Grouse and Black-backed Woodpecker. The plateau of northern Cape Breton Island was occupied by a forest of almost pure Balsam Fir which was largely killed by spruce budworm defoliation in the mid-to-late 1970s. Most of the dead forest has been clearcut and areas are being replanted with spruce, with unknown consequences for the birds that once nested there or may nest there in future. In very exposed coastal or highland forests where the spruce may form a dense, stunted krummholtz, northern or mountain species such as Gray-cheeked Thrush, Blackpoll Warbler and Fox Sparrow may be found nesting.

Within the coastal forest and also in the Cape Breton Highlands are extensive bogs and barrens, the barrens often with wide expanses of bedrock and massive glacial boulders (as in the well-known barrens around Peggy's Cove, Halifax County). Although these are arctic or alpine in appearance, this is a consequence of thin and often acidic soil, the result of the sweep of glaciation or sometimes soil-destructive fires, rather than severe climate. Thus, except for a few nesting Greater Yellowlegs on Cape Breton Island and the northern mainland, the avifauna of these barren landscapes is not particularly northern in flavour. Rather, such species as Palm Warbler, Savannah Sparrow and Swamp Sparrow are commonplace.

The largest portion of the province has forests typical of the Acadian Forest Region. Toward the south and southwest, conifers predominate, and hemlock, red spruce, and white and red pine are important. Red oak, sugar maple, and yellow and white birches are also present in varying admixtures. Deciduous trees are more abundant towards the north and east, along the slopes of the North and Cobequid mountains and on the mountain slopes of Cape Breton Island. Most forests in Nova Scotia have been cut over, burned or clearcut for farming, and the second-growth forests are often quite different in species composition from the original stands.

In the more coniferous parts of the forest, the Hermit and Swainson's Thrush, several wood warblers and the Dark-eyed Junco are conspicuous, together with a great number of species characteristic of boreal forests in southern and central Canada (Erskine 1977). Broad-leaved forests sustain a different assemblage of birds, depending on stage of succession (Nova Scotia examples in Freedman et al. 1981). Species such as the Common Yellowthroat, Chestnut-sided Warbler and White throated Sparrow are common on clearcuts, and the Least Flycatcher, Red-eyed Vireo and Ovenbird are found abundantly in more mature stands.

Here and there glacial or riverine deposits have produced soils suitable for farming, although there are no Grade-l agricultural soils in Nova Scotia. The most extensive agriculture is in the Annapolis Valley, a depression some 140 km long by 4-12 km wide, running from the Minas Basin in the northeast to St. Mary's Bay in the southwest. Extensive mixed farming in the valley, including the famed apple orchards, have produced habitats for birds (e.g., Eastern Meadowlark and, formerly at least, Eastern Bluebird) that have not nested elsewhere or do so rarely. The small old towns in the valley, which is more "summery" than the Atlantic coastal regions, have nesting birds such as the Northern Oriole that are uncommon elsewhere. In winter, waste grains in fields and around grain-storage facilities support large numbers of crows, flocks of blackbirds and the province's only substantial populations of Ring-necked Pheasants. Raptors are also more common, no doubt attracted by well-fed rodent populations.

Nova Scotia has a multitude of ponds, lakes and streams. Those of hardrock regions are highly acidic and generally have little or no emergent vegetation. Common Loons and some duck species nest on large lakes and smaller bodies of water, and bogs may have Common Snipe and a variety of water-associated land birds, such as Rusty Blackbirds. However, in general these more acidic waters support little birdlife, and their productivity may have been impaired in recent years by the effects of acid rain (the earlier-mentioned wind patterns of eastern North America bring industrial pollution from points west and southwest). Birdlife is much richer on ponds and streams in the less acidic parts of the province, notably in the Annapolis Valley, near the New Brunswick border and in scattered localities elsewhere. In these waters, emergent vegetation, such as cattails, and sometimes the enhanced aquatic productivity resulting from urban or agricultural runoff, encourages a much greater variety of water and marsh birds; American Bitterns, teal species and Red-winged Blackbirds are typical, and the first nestings of a number of waterfowl, as well as such birds as Black Tern and Common Moorhen, have occurred in such productive waters near the New Brunswick border.

The marine waters around Nova Scotia derive from the Gulf of St. Lawrence and the Labrador Current, a part of which curls south of Newfoundland and across the Scotian Shelf. The shallow Northumberland Strait warms considerably in summer, but the waters of the Scotian Shelf and the Bay of Fundy remain cold, especially the latter in which much tidal mixing with deep, cold water occurs. The warm Gulf Stream passes considerably to the south, outside territorial limits, although large, warm eddies detach at times and bring tropical waters over the Scotian Shelf.

The distributions of nesting inshore seabirds such as cormorants, Common Eiders, gulls and terns depend more on the availability of suitable nesting sites than on the character of the local waters, although the more turbid parts of the Bay of Fundy may be avoided. Wintering seabirds such as loons, grebes and sea ducks are widely distributed on all sorts of coasts.

The presence of truly pelagic seabirds almost defines our offshore waters. An extensive account of the distribution and seasonal abundances of such species in relation to the offshore environment is given by Brown et al. (1975). Our pelagic birds are mostly coldwater species that nest in the region, such as Leach's Storm-Petrel and Black-legged Kittiwakes, or come from further north, such as the Northern Fulmar and Dovekie. However, three subantarctic breeders, Greater and Sooty Shearwaters and Wilson's Storm-Petrel, predominate during summer. Our waters are not suitable for tropical or subtropical seabirds, which generally occur here as storm-driven vagrants; however, the outer limits of our pelagic zone have not been adequately explored, and some warmwater species may prove regular there.

Next Page