Nature Trust of New Brunswick

Manawagonish Island – Saint John, NB

Photo Credit: Nature Trust

Saint John, New Brunswick


This nature preserve of approximately 20 hectares (48 acres) consists of Manawagonish Island and Thumb Cap Island. They lie in the Bay of Fundy 1.5 km off Saint John. They are easily viewed from the Irving Nature Park. Manawagonish Island is an important sanctuary for sea birds.


The islands were donated to the Nature Trust in 1992 by the previous four owners who wish to remain anonymous. New Brunswick Museum scientists assisted with the acquisition of the site as well as with bird banding and research. Research on the effects of pesticides on seabirds was conducted on this island from 1940 to 1994 by New Brunswick Museum scientists, Will Astle (an enthusiast from New York) and by the Canadian Wildlife Service. There is a considerable amount of information on the establishment and changes that have taken place in this seabird colony.

Because the island now lacks trees large enough for the building of sea bird nests, in 2007 the Nature Trust, with the assistance of Marwood Ltd of Fredericton and J. D. Irving Ltd. of Saint John used helicopters to erect 5 poles with 20 platforms suitable for nests. Many of these have proven successful nesting sites.


The island, also known as Mahogany Island in the past, was originally covered with typical coastal forest of spruce and fir, but the increase in the bird population has led to great changes in the vegetation. Little now remains of the original forest. Today there are many double-crested cormorants, herring and greater black-backed gulls, great blue herons and common eider nesting on these islands. The rain of guano has led to the establishment of a diverse lichen flora on the cliffs.

Access and Activities

The islands may only be accessed by boat. Persons wishing to land on the islands should contact the Nature Trust since, during some seasons, the nesting birds may be very easily disturbed.

*No visiting is allowed between May 15 and August 15 due to the bird breeding season. For more information, please review Environment Canada’s guidelines to avoid disturbance to seabird and waterbird colonies in Canada. The property is undeveloped and there are a variety of hazards and risks associated with accessing this preserve. While this nature preserve is open for public access, visitors must assume responsibility for their own actions and safety and are to use the land at their own risk.*

View or navigate to this preserve via Google Maps.

Click the map below for more detail.


The Nature Trust of New Brunswick
404 Queen St. 3rd floor
P.O. Box 603, Station A
Fredericton, New Brunswick E3B 5A6
Phone: (506)457-2398
Fax: (506)450-2137

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