Description of Residence for the Ross’s Gull (Rhodostethia rosea) 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 Ross’s Gull 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 Ross’s Gull (Rhodostethia rosea) was created for the purposes of increasing public awareness and aiding enforcement of the above prohibition. Ross’s Gulls are known to have one type of residence – the nest.
Common Name – Ross’s Gull
Scientific Name – Rhodostethia rosea
Current COSEWIC Status & Year of Designation – Threatened (2001)
Occurrence in Canada –Manitoba and Nunavut (Figure 1).
Rationale for Designation –Very small population with low productivity1.
Figure 1. Known Ross’s Gull (Rhodostethia rosea)breeding locations in Canada.
1) The Nest
Physical Appearance and Context
Any site used by a Ross’s Gull for nesting is considered a residence. Ross’s Gulls mainly breed in the Old World Arctic, but a few breeding locations are known in Canada1. Ross’s Gulls are known to breed in varied habitats. The most common breeding habitat is marshy wetland in subarctic and boreal tundra2. However, they are also known to use high arctic tundra and gravel reefs3, 4. The breeding habitat around Churchill is wet tundra with small pools, hummocks supporting grasses, lichens and dwarf willows (Salix sp.), and lower areas with grasses and sedges1,3. On Prince Charles Island, Nunavut, the gulls nested in an area of poorly vegetated, dry tundra and gravel, surrounded by a network of medium-sized lakes4. At much higher latitudes on the Cheyne Islands, Nunavut, the gulls have been found nesting on reefs1 (small, low gravel islands supporting freshwater ponds and with prominent vegetation, mostly mosses). The only nesting requirement seems to be the presence of open water, such as lakes, ponds, or open leads in the pack ice3. Also, nests are often located in areas near Arctic Tern (Sterna paradisaea) colonies3.
Ross’s Gull nests can be a depression in the ground (a ‘scrape’), moss cup, or located in sedge tussocks3. Nests are approximately 10-15 cm in diameter and are lined with vegetation, such as dry grass, sedge, moss, willow or birch leaves, or seaweed3. The eggs are olive with faint reddish-brown markings5, and are approximately 30 x 43-46 mm4. Clutch size is generally three, but may contain one or two eggs. Nests are incubated by both parents3, for 21-22 days5, and chicks fledge at 20+ days after hatch5. In Canada, chicks hatch approximately mid-July3.
The function of the nest residence is to provide protection, shelter, and the required conditions for egg laying, incubation, and hatching, as well as the post-hatch rearing of young.
Damage or Destruction of the Residence
Any activity that destroys the function of nest would constitute damage or destruction of the residence. This would include, but is not limited to, preventing access to the nest, moving, taking or otherwise disturbing the eggs, destroying the nest, or changes to the microclimate of the nest. Ross’s Gulls are known to be disrupted by the presence of bird-watchers, photographers or tourists, and may have lower breeding success if disturbed. There is one known incident of a nest being abandoned because of a photographer beside the nest1. Approaching nests closer than 50 m is undesirable1, and should be avoided.
Period and Frequency of Occupancy
The nest should remain protected as a residence from the time of construction until the chicks fledge. This will typically occur between early June and early September each year.
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