Description of Residence for Whooping Crane (Grus americana) 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 Whooping Crane is under pre-existing 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 is a description of residence for the Whooping Crane (Grus americana), created for the purposes of increasing public awareness and aiding enforcement of the above prohibition. Whooping Cranes are known to have one type of residence – the nest.
Common Name – Whooping Crane
Scientific Name – Grus americana
Current COSEWIC Status & Year of Designation – Endangered (1978, 2000)
Occurrence in Canada –Nests in Northwest Territories and Alberta (Figure 1). Migrates through Saskatchewan and northeastern Alberta. Subadults occasionally summer in Saskatchewan, Alberta and Manitoba. Accidental (rarely sighted) in British Columbia.
Description of Figure 1
Whooping Cranes formerly bred in isolated marshes on the prairies and in aspen parkland. There are six primary nesting areas within and adjacent to Wood Buffalo National Park; between the headwaters of the Nyarling, Sass, Klewi and Little Buffalo rivers. The area is poorly drained and interspersed with numerous potholes. Wetlands vary considerably in size, shape, and depth, and most possess soft marl bottoms (Timoney et al. 1997). The wetlands are separated by narrow ridges, which support an overstorey of white spruce (Picea glauca), black spruce (P. mariana), tamarack (Larix laricina), and willows (Salix spp.) and an understorey of dwarf birch (Betula glandulosa), Labrador tea (Ledum groenlandicum), bearberry (Arctostaphylos uva-ursi), and several species of lichen, underlain by sphagnum moss (Novakowski 1966). Bulrush (Scirpus validus) is the dominant emergent in the potholes used for nesting, although cattail (Typha sp.), sedge (Carex aquatilis), musk-grass (Chara sp.), and other aquatic plants are common (Allen 1956; Novakowski 1965, 1966; Kuyt 1976a, 1976b, 1981). Nest sites are located primarily in shallow diatom ponds that contain bulrush (Timoney 1999).
Rationale for Designation – The Whooping Crane population is small at approximately 200 individuals and has slow reproductive potential due to delayed sexual maturity and small clutch size. In addition, the breeding and wintering areas are restricted in size making the population vulnerable to natural and human-caused catastrophic events. Habitat loss and degradation, disturbance and competition from other wildlife species on the wintering grounds, and human population growth in south Texas which reduces freshwater inflows into crane habitat are the most serious threats1.
1. The Nest
Physical Appearance and Context
Whooping Crane nests are protected as residences. Typically Whooping Cranes build an open nest with a shallow depression for the eggs, measuring approximately 1metre across. Both members of the pair actively construct the nest over a period of several days. The nest is usually situated in a stand of emergent vegetation either built up from the bottom of the pond or floating. Average water depth at nest sites is about 25 cm. Nests are constructed of surrounding material such as bulrush, sedge, cattail and moss or any combination of those (Figure 2). Nests are occasionally anchored to the base of a small willow. Although Whooping Cranes maintain a defended territory each breeding season the only location that can be considered a residence is the nest.
Clutch size averages two eggs, light brown or olive buff in colour, marked with dark blotches of various sizes concentrated near the large end of the egg4 (Figure 3). Young birds areprecocial (mobile within hours of hatching). The adults may use the nest to brood the young for 1 or 2 days post hatch before leaving the nest pond2.
The function of the nest residence is to provide protection, shelter, and the required conditions for egg laying, incubation, and hatching, as well as brooding hatchlings.
Damage and Destruction of the Residence
Any activity that destroys the function of nest would constitute damage or destruction of the residence. Whooping Cranes are sensitive to disturbance. Breeding pairs, although aggressive to intruders near the nest, may abandon the nest with prolonged or repeated disturbance by a predator, humans or low flying aircraft. Damage and destruction can be physical in nature or a disturbance that would cause the cranes to abandon the nest.
Period and Frequency of Occupancy
Whooping Cranes defend the same breeding territory from one year to the next. They typically arrive on their territories in late April or early May. Upon arrival they reestablish their territory through unison calling and actively chasing off intruders. Once the territory is established they begin nest construction. Whooping Cranes almost always change nest sites from year to year, however some pairs may use the same nest pond as previous years3.
The nest should be protected during the building, laying, incubation, hatching and immediate post hatching periods, a time frame of approximately 45 days at each site during the nesting period of April 15 - June 30 for each year.
1 Canadian Wildlife Service and U.S. Fish and Wildlife Service. 2004. International recovery plan for the Whooping Crane. Ottawa: Recovery of Nationally Endangered Wildlife (RENEW), and U.S. Fish and Wildlife Service, Albuquerque, New Mexico. 158 pp.
2 Johns, B. 2004. Canadian Wildlife Service. Personal Communication.
3 Kuyt, E. 1993. Whooping crane, Grus americana, home range and breeding range expansion in Wood Buffalo National Park, 1970-1991. Canadian Field Naturalist 107:1-12.
4 Kuyt, E. 1995. The nest and eggs of the whooping crane, Grus americana. Canadian Field Naturalist 109:1-5.
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