COSEWIC Assessment and Status Report on the Red Knot in Canada
- Assessment Summary
- Executive Summary
- COSEWIC History, Mandate, Membership and Definitions
- Lists of Figures and Tables
- Species Information
- Population Sizes and Trends
- Limiting Factors and Threats
- Special Significance of the Species
- Existing Protection or Other Status Designations
- Technical Summary
- Acknowledgements, Authorities Consulted, and Information Sources
- Biographical Summary of Report Writers and Collections Examined
The global distribution of the six currently recognized subspecies of Red Knots is shown in Figure 1 and described in the subspecies section.
Wintering Grounds (outside Canada)
The major wintering areas used by rufa knots were discovered in Tierra del Fuego and Patagonia, Argentina and Chile in the 1980s by Morrison and Ross (1989). In the 1980s, sites in Tierra del Fuego and Patagonia held 79% and 21% of the southern wintering population of birds, but by the early 2000s, Tierra del Fuego held about 98% of the total and the “peripheral” sites in Patagonia held only about 2%. The population thus appears to have contracted to the core sites, leaving few birds at the Patagonian sites (Morrison et al. 2004). The major wintering areas used by roselaari type knots include the i) Pacific coast of the Americas, from California south to Baja California and parts of northwest Mexico around the Gulf of California (Pacific coast population), ii) southeastern US including Florida and Georgia, with smaller numbers in South Carolina and Texas (Florida/SE US population) and iii) Maranhão on the north-central coast of Brazil (Maranhão, Brazil population). Islandica knots winter on the European seaboard (Salomonsen 1950; Godfrey 1953, 1986; Morrison 1975).
The breeding range of C. c. rufa falls entirely within the central parts of the Canadian Arctic, while about 40% of the breeding population of C. c. islandica breed in the northeastern Canadian Arctic. Knots breeding in northern and western Alaska and the western Canadian Arctic belong to roselaari type (Figure 5).
Within the central Canadian Arctic, suitable habitat is not continuous, so there are discontinuities within the range and it appears that not all suitable potential habitat is occupied (Figure 6). Rufa breeds on Coats and Mansel islands in northern Hudson Bay, on Southampton Island, on the east coast (Godfrey 1986) as well as the islands of the Foxe Basin (e.g., Prince Charles Island, Rowley Island, but not on Air Force Island (V. Johnston pers. comm. 2005) and the west coast of Baffin Island (RIGM pers. observation; Niles et al. 2005), probably through the Boothia Peninsula area, on King William Island, and on the southern parts of Victoria Island (Parmelee et al. 1967). Suitable habitat does not appear to occur on land between northern Hudson Bay and the Rasmussen Basin (Niles et al. 2005), and the species was not recorded in this area (Godfrey 1986, 1992) or in the Rasmussen Lowlands (Johnston et al. 2000). Rufa appears to breed on the west side of the Boothia Peninsula and on King William Island (Niles et al. 2005), but it is replaced by islandica on Prince of Wales Island to the north (Manning and Macpherson 1961; Godfrey 1992). Although there appears to be suitable habitat on Banks Island at the western edge of the Arctic Islands, knots have not been recorded breeding in this area (Manning et al. 1956; V. Johnston pers. comm. 2005).
C. c. rufa occupies areas in the Central Canadian Arctic, and breeds entirely within Canada. C. c. roselaari populations wintering in Florida/SE US and Maranhão may share parts of this range, most likely towards the western portion. C. c. roselaari wintering on the Pacific coast of the Americas occupy breeding areas in northwestern Alaska (and Wrangel Island). Knots in the High Arctic regions of northeastern Canada and of Greenland are C. c. islandica. Broken lines enclose overall likely range of each subspecies and solid areas represent likely occupied suitable habitat within the range.
Figure 6: Predicted Locations of Nesting Habitats of Red Knots Based on Land Cover Types in the Central Canadian Arctic (and point locations [circles] of Red Knots located on the nesting grounds after being radio-tagged in Delaware Bay during northward migration)
From Niles et al. 2005.
C. c. roselaari wintering on the Pacific coast of the Americas occupy breeding areas in northwestern Alaska and Wrangel Island. Breeding grounds occupied by Florida/SE US and Maranhão wintering populations are not clearly delineated, but are likely to involve the more westerly parts of the breeding range in Canada. Onepiece of evidence to support this hypothesis is the recovery of a banded bird wintering in Florida in Manitoba on northward migration. This recovery suggests that it was headed towards the western end of the range as opposed to going up the Atlantic coast to the eastern breeding grounds.
The estimated extent of occurrence (EO) of rufa based on a compilation by the Canadian Wildlife Service (A. Baril, pers. comm. 2005) of breeding range maps from NatureServe, WildSpace, and Birds of North America is 205 534 km2. The area of occupancy (AO), or area of suitable habitat occurring within this range, is 128 375 km2 (97 750 km2 <50 km from coast plus 30 425 km2 >50 km from coast; based on potential suitable habitat types, see Figure 6, R. Lathrop, pers. comm. 2005). The estimated EO for the Florida/SE US and Maranhão, Brazil populations of C. c. roselaari is an unknown portion of the EO (i.e. 205 534 km2) assigned to rufa (i.e. it may overlap with some portion of rufa’s range) and the EO for the Pacific coast population is 41 396 km2, which includes the breeding grounds in Alaska. The AO for the Florida and Maranhão populations is some unknown portion of the AO for rufa (i.e. 128 375 km2), while the AO for the Pacific coast population is 25 856 km2 based on suitable breeding habitat in Alaska. The estimated EO for islandica is 455 669 km2, which includes their breeding range in Canada. The AO for islandica in Canada is 284 611 km2 based on suitable habitat.
On migration, large numbers of knots pass southwards through the southwest coast of Hudson Bay (Manitoba and Ontario) and west and southern coasts of James Bay during July and August (Ontario) (Hope and Shortt 1944; Manning 1952; Ross et al. 2003). The southeast corner of Akimiski Island also appears to be important for knots. Knots have also been recorded in small numbers (100-350) on the south coast of James Bay in Quebec (Aubry and Cotter 2001a).
The most important areas for rufa knots on migration in eastern Canada are currently along the north shore of the St. Lawrence River in Quebec (Figure 7). The sightings in theMinganIslandsarchipelago in 2006 of many colour-marked birds that had been captured in Argentina confirm the identity of the birds as belonging to the rufa population wintering in southern South America (Y. Aubry, pers. comm. 2006). Ouellet (1969) identified four knots collected from a flock of 200 on Anticosti Island as belonging to the rufa subspecies.
During northward migration, large flights of knots have been observed passing northwards through southern James Bay at the end of May or start of June (RIGM unpubl. data), having probably flown directly from Delaware Bay (Morrison and Harrington 1992). Large concentrations are occasionally found around Lake Ontario, though these probably represent weather-related dropouts from the main migration (McRae 1982; Weir 1989; see Morrison and Harrington 1992). The sighting of a bird colour-banded at Lagoa do Peixe in southern Brazil at Presqu’ile Provincial Park indicates the birds include migrants from the southern rufa population.
Locations shown on the map are: 1. Southwest coast of Hudson Bay (MB, ON) and west and south coasts of James Bay (ON, QC); 2. Saguenay River mouth, St. Lawrence River, QC; 3. Mingan Archipelago, north shore of St. Lawrence River, QC; 4. Miscou Island, NB; 5. Magdalen Islands, Gulf of St. Lawrence, QC; 6. North shore Prince Edward Island; 7. Upper Bay of Fundy (Mary’s Point), NB; 8. southern Cape Breton Island, NS; 9. Grand Manan Island, NB; 10. Cape Sable, NS. (Information compiled from Hope and Shortt 1944; Morrison and Harrington 1979; Morrison et al. 1980; Morrison and Gaston 1986; Hicklin 1987; Aubry and Cotter 2001a; Roberge et al. 2001; Ross et al. 2003; R.I.G. Morrison unpubl. data from Maritimes Shorebird Survey; R.K. Ross and R.I.G. Morrison unpubl. data from Hudson Bay and James Bay aerial surveys, EPOQ database pers. comm. Yves Aubry).
Less information is available to identify migration areas used by roselaari type knots wintering in Florida/SE US and Maranhão. Both groups are known to pass through Delaware Bay during the spring. However, a significant proportion of these groups likely migrates to the breeding areas through the interior of North America, as indicated by a band recovery of a bird wintering in west Florida in Manitoba during spring migration. The Pacific coast population of C. c. roselaari migrates down the Pacific coast of North America, including through coastal British Columbia.
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