Population status

Red Knot
(Calidris canutus)

An assessment of the status of the national population of the Red Knot relies on the individual assessments of two of the three subspecies that occur in Canada, given that C.c. roselaari occurs in very small numbers and is therefore unlikely to influence the national status. In general, it appears that the Red Knot population in Canada has undergone a moderate decrease since about 1970, though trends differ among the subspecies and there is a paucity of data extending back to the 1970s. Thus, the reliability for this assessment is considered to be low.

Results from continental migration monitoring efforts, which likely represent rufa given that islandica winters in Europe, suggest a large decrease (-5.7% per year, see below), though precision is low and the proportion of birds monitored by these surveys is unknown. This result is consistent with other work done on rufa: aerial survey counts on the southern wintering grounds in Tierra del Fuego have shown an 80% decrease in population since 1982 (Morrison and Ross 1989, Andres et al. 2012). Surveys of wintering and stopover sites suggest a decrease during the 2000s, followed by a period of relative stability at lower levels than were seen in the 1980s and 1990s (ECCC 2017d). The wintering populations in Florida and northern Brazil have shown decreases of about 50% since the early 1980s (Dey et al. 2011, Andres et al. 2012). The global population is estimated to be about 42,000 individuals (Andres et al. 2012).

The islandica subspecies is believed to be the most numerous of the six recognized subspecies worldwide, with a global population of about 80,000 birds (Meltofte 2004, Andres et al. 2012). Winter counts in Europe suggest that the population of C. c. islandica has shown long-term fluctuations over the last 40 years (COSEWIC 2007f), but overall has shown little change or perhaps a slight decrease from the mid-1980s to 2015 (van Roomen 2015). The reliability of this assessment is considered to be low, because these winter surveys represent an unknown proportion of Canadian birds, and do not cover the entire winter range of the subspecies.

There is also considerable uncertainty about the size of the C.c. roselaari population because knowledge of the subspecies’ wintering distribution is incomplete (ECCC 2017d). Recent mark-resighting work estimates the global population to be about 17,000 (Andres et al. 2012); numbers previously reported to pass through Alaska on migration have varied widely from 20,000 to 110,000 (Buchanan et al. 2010, Niles et al. 2010, Morrison et al. 2006), though the number passing through Canada is thought to be <1% of the global population. COSEWIC 2007f and ECCC 2017d indicate that the subspecies has conservatively decreased by 47% over the last 15-20 years.

The national population goals for rufa and roselaari are drawn from the species’ Recovery Strategy and Management Plan (ECCC 2017d). The national goal for rufa is, at minimum, to bring the population back to levels observed in the late 1980s/early 1990s (100,000-150,000 individuals); the goal for islandica is to maintain the population at current levels (~80,000 individuals). The recovery goal for roselaari is based on the maintenance of stopover sites, which would support the current population of migrants (~170 individuals). The national population goal for roselaari is therefore the maintenance of current population levels. All three subspecies are considered to be below the lowest acceptable level relative to their national population goals until they are de-listed under the Species at Risk Act.

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Red KnotNot applicableNot applicableNot applicable
Red Knot islandica subspeciesLong-term recovery goal (SARA)Equal to goalNot applicable
Red Knot roselaari typeLong-term recovery goal (SARA)Equal to goalNot applicable
Red Knot rufa subspeciesLong-term recovery goal (SARA)Equal to goalNot applicable

Analyses of Shorebird Migration Monitoring Data

Additional information on: Analyses of Shorebird Migration Monitoring Data

Table 1: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 1 - footnote 1 Limits
LowerUpper
North America Select to view graph of the geographic area: North America 1974-2016; Analyses of Shorebird Migration Monitoring Data1974-2016-5.7-10.2-0.6
 

References