Ted C. D'Eon - February 1996


  • The Roseate Tern (Sterna dougallii).

  • Committee on the Status of Endangered Wildlife in Canada (COSEWIC) status - threatened.

  • Roseate Tern Recovery Plan established in 1992 - chaired by Dr. Sherman Boates of the Wildlife Division of the Nova Scotia Department of Natural Resources.

    There are two small islands near my home in West Pubnico where Roseates have been nesting since at least 1982. On the more recent charts, these islands are referred to as "The Brothers". On older charts they were known as the "Twin Islands". The first time Roseate Terns were noticed there by the local birders was on May 26, 1983 when a group of us, on our yearly census visit to the island bird colonies, stopped on The Northern Brother (Northern "Twin Island"). Delisle d'Entremont of Lower West Pubnico, brought our attention to about 40 Roseates, from a colony of 1000, mostly Common terns. Since then I have been observing their yearly progress. In 1983 we were not aware that during the previous Summer, Dr. Tony Lock, of Canadian Wildlife Service, had already located Roseates in this colony.

    In Atlantic Canada, Roseates will be found nesting with Common and/or Arctic Terns in only a very few tern colonies. The easiest and fastest way to establish their existence in a colony is by their call. Once the observer's ears become sensitized to their short and raspy "aaak" alarm call, locating the birds becomes quite simple. After hearing its distinctive call, one must look in the direction of the sound for a tern of whiter appearance with a longer white streaming tail. Its upperwing is mostly very pale grey. The primaries often appearing as a dark grey leading edge. At the time of their arrival to "The Brothers", around mid-May, the bill of the adult Roseate Tern is completely black. Later, as Summer progresses, the bill will begin to show more and more red-orange on it's basal half. Also, the faintly rosy underparts may help to assure identification.

    On May 7, 1991, from a suggestion by Dr. Ian C. T. Nisbet of the Massachusetts Audubon Society, at our 1990 Atlantic Canada Tern Working Group (ACTWoG) meeting, I placed my first Roseate Tern nesting boxes on "The Brothers". These had a 16 in. x 16 in. plywood top and three 5 in. high sides. The fourth side was left open as an entrance to the shelter; there was no floor. A heavy rock was placed on top of the structure so it would not be blown away. The structures worked, and with some nest identification pointers from Dr. Tony Lock, I was even able to identify my first Roseate Tern nests outside of these and other shelters.

    Nest and egg identification is difficult at its best. The preferred nesting habitat generally provides more cover than what we see for Common and Arctic Terns. They usually nest adjacent to clumps of vegetation, under boulders, under washed up wooden boards and planks and other driftwood where they can find shelter or seclusion. They, however, like the proximity of others of their kind and therefore form a sub-colony within the tern colony as a whole.

    Roseate Terns usually lay one or two eggs, rarely more. The eggs are laid 2 or 3 days apart, and hatch accordingly. The nest itself may be a shallow scrape with little nesting material, but from my observations on "The Brothers", the Roseate nests there, generally contain more plant material than those of Common and Arctic Tern's. Pieces of plant stalks (6 to 15cm long) from previous years growth, give the nest the appearance of varying amounts of matted straw.

    Egg colour and size variations among our three species, present another problem. The eggs are usually longer and narrower than those of Common and Arctic Terns. The eggshell background colour is usually light sandy-brown (rarely with olive, and never with blueish cast)with blackish-brown speckles, spots, and scrawls more apt to be on the larger end. The markings are usually finer than those of the other species.

    The Common and The Arctic Tern may lay eggs which also fit the above field marks, but their eggs are more likely to be rounder and darker, with larger spots and speckles, and the eggshells background colour with a blueish, pale greenish or olive cast.

    Identifying the Roseate Tern nestling in these colonies presents no problem, even to the novice. The filament tips of the greyish-brown down of the young Roseate Tern is gathered in tufts (even when dry) giving it a spiky appearance. The legs and feet of the newly hatched start out purpleish-pink but within a few days darken to almost black. Those of the Common and Arctic's are yellowish-orange to orange.

    Since 1989, I have been collecting data on the tern colonies of the Lobster Bay Area and reporting my findings to Canadian Wildlife Service and the Nova Scotia Department of Natural Resources (NSDNR), Wildlife Division.

    The following table shows the tern nest count breakdown from 1991 to 1995 on the Northern Brother.

                    1991    1992    1993    1994    1995
     Total nests     454     413     367     380     457
     Roseate nests    20      23      30      34      33

  • Tern Report-1997
  • In 1993, the Nova Scotia Department of Fisheries issued a permit to some local fishermen to place an aquaculture structure in the waters adjacent to the Northern Brother. This was after the NSDNR, Wildlife Division had been working a couple of years acquiring and getting clear title to the lands of "The Brothers" in an attempt to create a wildlife management area, since, at this time, the Northern Brother comprised the only recognized Roseate Tern colony in Canada. A couple of years earlier work was begun for a Canadian Roseate Tern Recovery Plan of which I am still a member. We had a concern that the aquaculture operation could disturb the tern colony enough to reduce its productivity, or worse, by the twice daily ins and outs of the fishermen and the possible increase in the gull density near the island. We felt it was very poor judgement on the part of the Minister of Fisheries.

    However, it was done. On May 9, 1994, an aquaculture pen was towed in place and anchored to the east of the island. The first fish (Steelhead Trout) were placed into it on May 16.

    As it turned out, the aquaculture activities did not seem to disturb the terns, and they nested well. Gulls were not attracted to the area even when the fish were being fed. 1994 was, however, a poor year for egg hatching and fledgling success. Only about 18% of the eggs hatched and very few chicks fledged. It would be easy to say aquaculture was the cause but from my observations, I do not believe it to be so. Instead, the poor, wet and cold weather during the incubation stage and the appearance of a Snowy Owl in early July were likely the major candidates.

    The 1995 nesting season on the Northern Brother was superb, eventhough the aquaculture project had expanded to four pens. Fledgling success was high. The Roseate Terns did well.

    The NSDNR, Wildlife Division has now identified two more tern colonies in Nova Scotia, containing numbers of Roseate Terns similar to those of "The Brothers".

    Ted C. D'Eon

    P.O. Box 100 West Pubnico Nova Scotia B0W 3S0 Canada phone - Home 1-902-762-2097 - Work 1-902-762-2793 - FAX 1-902-762-2885
    Send E-Mail to: deonted@fox.nstn.ca

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    © Ted C. D'Eon, 1996