Population status

Loggerhead Shrike
(Lanius ludovicianus)

There are two subspecies of Loggerhead Shrike in Canada, excubitorides, which breeds in the Prairies, and migrans, which breeds in Ontario. However, recent genetic work suggests that the Loggerhead Shrike population in Ontario should be considered a unique subspecies separate from migrans. The larger Prairie population is monitored by the Breeding Bird Survey (BBS), which provides good coverage of the breeding population (see results for Prairie Potholes Bird Conservation Region [BCR] below). The migrans population is smaller, resulting in fewer detections during BBS surveys, and less reliable trends (see data for Lower Great Lakes/St. Lawrence Plain BCR below). Current BBS results indicate that both populations have undergone large, long-term decreases relative to about 1970. Further evidence of declines in the Prairie provinces is provided by dedicated Loggerhead Shrike surveys (Environment Canada 2015a) which show similar levels of decline, although differences in methodology and coverage between the two surveys make direct comparisons difficult. Once a regular breeder in the St. Lawrence lowlands in Québec, the migrans subspecies has become extremely rare and irregular in that province; it was observed in one atlas square in the most recent Quebec atlas as compared to 30 in the first atlas (Atlas of the Breeding Birds of Quebec 2017). The excubitorides subspecies of the Loggerhead Shrike is below the lowest acceptable level relative to its national population goal (see BBS Prairies Potholes graph below), which is consistent with the Recovery Strategy's objective to stop the decline and maintain a stable or increasing population (Environment Canada 2015a). The migrans subspecies is also below the lowest acceptable level relative to its the Recovery Strategy's population objective, which is to re-establish a viable population (80 pairs) by 2040 (Environment Canada 2015b).

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Loggerhead ShrikeNot applicableNot applicableNot applicable
Loggerhead Shrike Eastern subspeciesLong-term recovery goal (SARA)Equal to goalNot applicable
Loggerhead Shrike Prairie subspeciesMean abundance (first 5 years of survey)Goal minus 25% Not applicable

Breeding Bird Survey (BBS) - Canadian analysis

Additional information on: Breeding Bird Survey (BBS) - Canadian analysis

Table 1: Population trends by geographic area
Geographic areaTime Period Table 1 - footnote 1 Annual trend Table 1 - footnote 2 Limits
LowerUpper
Canada Select to view graph of the geographic area: Canada 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-2.4-3.6-1.4
Canada Select to view graph of the geographic area: Canada 2006-2016; Breeding Bird Survey (BBS) - Canadian analysis2006-2016-0.5-2.83.1
Prairie Potholes Select to view graph of the geographic area: Prairie Potholes 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-2.4-3.5-1.3
Lower Great Lakes / St. Lawrence Plain Select to view graph of the geographic area: Lower Great Lakes / St. Lawrence Plain 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-9.1-12.3-6.2
North America Select to view graph of the geographic area: North America 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-2.5-2.8-2.3
 

References