Description of residence for Roseate Tern (Sterna dougallii) in Canada

Section 33 of the Species at Risk Act (SARA) prohibits damaging or destroying the residence of a listed threatened, endangered, or extirpated species. SARA defines residence as: “a dwelling-place, such as a den, nest or other similar area or place, that is occupied or habitually occupied by one or more individuals during all or part of their life cycles, including breeding, rearing, staging, wintering, feeding or hibernating” [s. 2(1)].

The prohibition comes into effect in different ways depending on the jurisdiction responsible for the species. As a migratory bird protected under the Migratory Bird Convention Act, the Roseate Tern is under federal jurisdiction. This means the residence prohibition is in effect on all lands on which the species occurs immediately upon its addition to the legal list of species at risk. 

The following description of residence for the Roseate Tern (Sterna dougallii) was created for the purposes of increasing public awareness and aiding enforcement of the above prohibition. Roseate Terns are known to have one type of residence – the nest.

Species Information

Common Name - Roseate Tern

Scientific Name - Sterna dougallii

Current Committee on the status of endangered wildlife in Canada (COSEWIC) Status & Year of Designation - Endangered (1999)

Occurrence in Canada - Nova Scotia, Québec, New Brunswick (Figure 1)

Rationale for Designation - Predation, competition, human disturbance.

Figure 1. Known breeding distribution of the Roseate Tern (Sterna dougallii ) in Canada.
Triangles indicate sites where terns have nested since 1982.

Known breeding distribution (See long description below)
Description of Figure 1

Global range: Breeds worldwide, usually on marine islands. In North America, a northeastern population breeds from the Gulf of St. Lawrence (Magdalen Islands) to New York; a disjunct Caribbean population breeds from Florida and the Bahamas to the Lesser Antilles.

Canadian range: Since 1982, have bred at about 28 sites, most of which are coastal islands in Nova Scotia, and of which 12 or fewer sites are occupied in any given year. The location of colonies changes unpredictably among years, and may not always be known even with extensive searches. Only three colonies are known to have had more than 20 pairs in the last 10 years: The Brothers (33-86 pairs), Grassy Island (0-30 pairs), and Country Island (0-53 pairs). In some years, have bred at a variable subset of other sites, including three of the Magdalen Islands, Québec, Machias Seal Island, NB, and about 21 other sites in Nova Scotia (Whittam 1999, Leonard et al. 2004; Appendix B).

Percentage of global distribution in Canada: Pairs breeding in Canada constitute 3-4% of the northwestern Atlantic population, and less than 1% of the (poorly) estimated world population (Gochfeld et al. 1998).

1) The Nest

Physical Appearance and Context

The residence of a Roseate Tern is the nest. Terns usually breed on coastal islands1. The nest is built on the ground, often hidden in a tuft of vegetation, under a rock pile or beach debris, or in the case of managed colonies, in specially provided nest shelters. When used, these structures would be considered part of a residence. It breeds in mixed colonies with Common Terns (Sterna hirundo) and Arctic Terns (Sterna paradisaea).1

The clutch usually consists of one or two eggs1. The eggs, approximately 43 mm x 29 mm, are various shades of brown, with blackish-brown spots and streaks1. At hatching, the chicks are covered with down and are capable of walking. If left undisturbed, they may remain in or near the nest (within 10 cm) throughout the brood-rearing period. If they are forced to leave, they will hide nearby in vegetation or under a pile of debris, and may move up to 60 m to denser cover1.

Function

The nest residence is essential to the sheltering, incubation, and hatching of eggs, and the rearing and feeding of young.

Damage and Destruction of the Residence

Any activity that destroys the function of the nest would constitute damage or destruction of the residence. This includes, but is not limited to, moving or otherwise disturbing the eggs; changing the microclimate of the nest (such as the amount of light or internal temperature); blocking access to the nest; or, in the case of colonies where nest shelters are used, affecting the functionality of nest shelters. Roseate Terns rely on large colonies of Arctic and Common Terns because the additional number of terns provides protection from predators. Therefore any actions or activities that have an impact on the colony could impair the functionality of a Roseate Tern residence through decreasing nest success.

Period and Frequency of Occupancy

The species is present at breeding colonies from mid-May to late August2. Since the nest may be used by the young for a prolonged period, it must be protected not only during nest building, laying, incubation and hatching, but also during brood rearing, or roughly during at least 60 days following nest construction.

Additional Information

For more information on the Roseate Tern

For more information on SARA.

References

1 J. Burger and I.C.T Nisbet. 1998. Roseate Tern (Sterna dougallii) In The Birds of North America, Number 370 (A. Poole and F.Gills, Editors). The Birds of North America,Inc., Philadelphia, PA.

2 Kirkham, I.R. and D.N. Nettleship. 1986. Status of the Roseate Tern Sterna dougallii in Canada. Committee on the status of endangered wildlife in Canada, Ottawa, Ontario