IBA Bon Portage Island
Shag Harbour, Nova Scotia
Site Summary
NS015 Latitude
43.519° N
65.746° W
0 - 10 m
3.00 km²
coniferous forest (temperate), tidal rivers/estuaries, freshwater marsh, open sea, inlets/coastal features (marine)
Land Use:
Nature conservation and research, Fisheries/aquaculture, Hunting
Potential or ongoing Threats:
IBA Criteria: Globally Significant: Congregatory Species, Colonial Waterbirds/Seabird Concentrations
Conservation status: Research Station (privately owned)
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Site Description
Bon Portage Island is located about 3 km off the southwest coast of Nova Scotia on the Gulf of Maine side. It is a low island, being comprised of two drumlins that are connected by a gravel and marsh isthmus. The vegetation is characterized by open coastal areas with inland areas of coniferous forest (spruce and fir), and small areas of freshwater marsh. The climate is maritime, with much fog and high humidity. There is little snow in the winter, and the tide ranges from 3 to 4 metres.

Bon Portage Island supports the largest known Leach's Storm-Petrel colony in the Maritimes (though few others have been studied seriously). During the late 1980s a breeding population of over 50,000 pairs was estimated. This is greater than 1% of the estimated western Atlantic population.

Of additional ornithological interest is the presence of a mixed species heronry. Great Blue Herons are the most abundant and about 10 pairs of nesting Black-crowned Night Herons have also been recorded. Since the late 1980s, Snowy Egrets have been present during the breeding season, but nesting has yet to be confirmed. The only other place Snowy Egrets have bred in Canada is in Southern Ontario.

Since the fall of 1995, a migration monitoring station has been operating on Bon Portage Island as part of The Atlantic Bird Observatory (a second station is operated on nearby Seal Island, which is located about 15 km to the west). Migration monitoring occurs during both the spring and fall with about 2,500 birds of 75 species banded every year.

IBA Criteria
SpeciesT | A | I Links Date Season Number G C N
Great Black-backed Gull 2016 FA 1,500
Herring Gull 2014 - 2016 FA 3,000 - 4,000
Manx Shearwater 2013 FA 50
Manx Shearwater 2016 - 2018 SU 4 - 12
Northern Gannet 2014 - 2015 FA 2,000 - 3,500
Roseate Tern 2015 SU 2
Savannah Sparrow 1993 - 2014 FA 21 - 24
Note: species shown in bold indicate that the maximum number exceeds at least one of the IBA thresholds (sub-regional, regional or global). The site may still not qualify for that level of IBA if the maximum number reflects an exceptional or historical occurrence.
Conservation Issues
The former lighthouse-keepers (the Richardsons) were keen naturalists, and helped in the transfer of the island to Acadia University for use as a research station. Currently, the seasonal presence of research staff and students results in controlled visitation. Ecotourism/birding is encouraged, and regulated, but may need more restrictions in the future. In addition to ownership by Acadia University, a small parcel of land is owned by the coast guard, and the marine and intertidal areas are overseen by the federal Fisheries and Oceans Department.

The IBA Program is an international conservation initiative coordinated by BirdLife International. The Canadian co-partners for the IBA Program are Birds Canada and Nature Canada.
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