Population status

Green Heron
(Butorides virescens)

The Breeding Bird Survey (BBS) provides the only long-term results for the Green Heron and suggests a moderate decrease in abundance since 1970 (all Bird Conservation Regions for which there are reasonably reliable BBS results in Canada are shown below). However, with the species' scattered breeding distribution, relative rarity and wetland breeding habitat, the BBS methodology is not ideal for this species (Davis and Kushlan 1994, Sandilands 2007a). With the majority of Canadian breeders in Ontario, the Atlas of the Breeding Birds of Ontario provides good coverage of the Green Heron population, though results only cover the 20-year period between the first and second Atlas. Atlas results also suggest a moderate decrease in distribution during this time, including significant decreases in the probability of observation in all regions where it nested (Sandilands 2007a). Results from the BBS suggest an even stronger decline at the continental scale. Overall, the Canadian population of the Green Heron has likely suffered a moderate decrease in abundance since 1970; the agreement between the surveys, despite their limitations, suggests a degree of high reliability. The Green Heron is currently below tthe lowest acceptable level relative to its national population goal (see Canada BBS graph below).

 

Population goal and acceptable levels of variation

Species/groupGoalLower levelUpper level
Green HeronMean 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 analysis1970-2016-0.8-1.70.2
Boreal Hardwood Transition Select to view graph of the geographic area: Boreal Hardwood Transition 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-0.8-2.61.2
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 analysis1970-2016-0.8-1.80.5
North America Select to view graph of the geographic area: North America 1970-2016; Breeding Bird Survey (BBS) - Canadian analysis1970-2016-1.7-2-1.5
 

Atlas of the Breeding Birds of Ontario

Additional information on: Atlas of the Breeding Birds of Ontario

Table 2: Population trends by geographic area
Geographic areaTime PeriodAnnual trend (%) Table 2 - footnote 1 Limits
LowerUpper
Ontario1981/85 - 2001/05-1.7-2.4-1
 

References