Population status

Dunlin
(Calidris alpina)

Dunlins winter along the Atlantic and Pacific coasts of North America, where they are well surveyed by the Christmas Bird Count (CBC). This survey suggests that the continental population has shown little overall change in abundance relative to 1970. However, the proportional representation of Canadian-breeding birds vs Alaskan-breeding birds is unclear. Dunlins are also surveyed by migration monitoring; results from this survey suggest a large decrease in abundance relative to about 1970. This discrepancy may suggest differences in trend among the subspecies of Dunlin. The majority of migration monitoring sites are in eastern North America, so the negative trend observed in these results may reflect trends in the eastern subspecies, C. a. hudsonia, which breeds in Canada. CBC counts are more evenly distributed across the continent, so these results may better reflect continental trends, because they include the much more abundant western subspecies, C. a. arcticola and C. a. pacifica, most of which breed in Alaska with smaller numbers in the Yukon (see numbers in Bart and Smith 2012). Therefore, based on migration monitoring results, which are more representative of Canadian breeders, the Dunlin is best assessed as having shown a large decrease relative to about 1970. However, contrasting CBC results indicate that confidence in this assessment could be improved by better monitoring information at the subspecies level. Future assessments of status may also be improved when results from the breeding grounds become available through the Arctic Program for Regional and International Shorebird Monitoring (Arctic PRISM). The Dunlin is currently below the lowest acceptable level relative to its national population goal (see migration monitoring graph below).

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
DunlinMean abundance (first 5 years of survey)Goal minus 25% Not applicable

British Columbia Coastal Waterbird Survey

Additional information on: British Columbia Coastal Waterbird Survey

Table 1: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 1 - footnote 1 Limits
LowerUpper
British Columbia coast1999-2016-10.7-14.5-6.6
 

Analyses of Shorebird Migration Monitoring Data

Additional information on: Analyses of Shorebird Migration Monitoring Data

Table 2: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 2 - footnote 1 Limits
LowerUpper
North America Select to view graph of the geographic area: North America 1974-2016; Analyses of Shorebird Migration Monitoring Data1974-2016-2.7-5.70.3
 

Picture of logo Christmas Bird Count (CBC)

Additional information on: Christmas Bird Count (CBC)

Table 3: Population trends by geographic area
Geographic areaTime PeriodAnnual Trend Table 3 - footnote 1 Limits
LowerUpper
North America Select to view graph of the geographic area: North America 1970-2016; Christmas Bird Count (CBC)1970-20160-1.41.54
 

References