Threatened Roseate Terns on Brothers Islands, Yarmouth County

by: J. Sherman Boates, Gerald Dickie, Ted D'Eon, and Jack Ryan
SUMMER/FALL 1992


Dramatic declines in roseate terns has led to their designation as a "Threatened Species". Photo: Ted D'Eon

Those who spend time near the ocean during the summer are familiar with the distinctive kee-ar-r-r call of a small, mostly white seabird called a tern. Tern's are remarkable birds. Known locally as "mackerel gulls," they can be seen flying gracefully like swallows, diving into the water, often leaving with a small fish in their bills. They likely spend more time in the air and more hours in daylight than any other animal. Terns' oceanic wanderings take them from extreme northern to southern latitudes which may exceed 35,000 km in a single year! Three species of terns-common, Arctic, and roseate-now nest in Nova Scotia, and it takes a fair bit of practice to tell them apart.

Historically, terns nested in abundance along much of the North Atlantic coast including on the coastal islands around Nova Scotia. Recently, there has been much concern because of a dramatic decline in both the number of colonies and the number of pairs of breeding terns in Atlantic Canada and the northeastern United States. The roseate tern, the least abundant of the three, has shown the largest decline in recent years. As a result, the roseate tern has been designated a "Threatened Species" by the Committee On The Status of Endangered Wildlife In Canada (COSEWIC).

The only known breeding colony of roseate terns in Nova Scotia is located on the Brothers Islands, Yarmouth County. Some may know them as the "Twin Islands."

The Brothers Islands consists of two small islands, each approximately 1/3 hectare (3/4 acre) in size. The islands have low, grassy vegetation and therefore primarily provide habitat only for nesting terns. Each year. since 1983, Ted D'eon of West Pubnico has been monitoring roseate terns on the islands. This summer he found 418 tern nests of which 23 were roseate tern nests. All roseate tern nests were found on the more northern of the two islands where most of the other terns also nested. During a visit on July 2 1 s', Ted saw a number of young roseates flying around and only found one dead chick. It appears that the roseate terns have had a relatively good breeding season.

Awareness of the importance of the Brothers Islands to the roseate terns has been through the Canadian Roseate Tern Recovery Plan and the Atlantic Management Plan for Marine Terns. In response to this, the province, through the Department of Natural Resources, recently acquired half interest in one of the Brothers Islands. As soon as the Crown acquires title to both islands it is proposed that the islands be declared a Wildlife Management Area. This declaration will include regulations for the protection and management of terns and their habitat but, on a restricted basis, will also allow for human use.

The Brothers Islands will be managed according to the Canadian Roseate Tern Recovery Plan. Interested individuals from the community, government, and other groups, will assist the Department of Natural Resources with management activities on the islands. These activities may include regular surveys of roseate terns and other seabirds and estimates of their reproductive success to act as indicators of the population's health.

The impact of gulls and other predators on terns will be assessed. Based on this assessment it may be necessary to use barriers to keep predators from tern nests or to implement a program of gull removal.

Small-scale habitat alterations may be carried out to improve nest habitat. For example, more artificial nest structures, which have been shown to increase reproductive success, may be placed on the island.

The Department of Natural Resources and the Canadian Wildlife Service are interested in all species of terns. Roseate terns have threatened status; however, common and Arctic terns have also both shown signs of decline. We are keen to hear of any new tern colonies that you have happened upon, or tern colonies that you have seen in the past, but that have declined in numbers or have even disappeared. It is difficult to identify all the tern breeding sites around the province, but with your help we can track changes in the distribution and abundance of these fascinating seabirds.


Roseate Tern eggs. Photo: Ted D'Eon