Justification of Red List Category
This species has an extremely large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend appears to be increasing, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.
The population size of Great Blue Heron is estimated at 500,000-4,999,999 mature individuals (Partners in Flight 2019).
Although trends differ between populations, the species overall appears to be increasing slowly (Partners in Flight 2019, Wetlands International 2020). Trends have been quantified across North America, where the population has been growing at >10% in total since the 1960s (Meehan et al. 2018, Pardieck et al. 2018).
The species is widespread across North and Central America as well as the Caribbean.
Text account compilers
Butchart, S. & Ekstrom, J.
BirdLife International (2021) Species factsheet: Ardea herodias. Downloaded from http://www.birdlife.org on 25/01/2021. Recommended citation for factsheets for more than one species: BirdLife International (2021) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 25/01/2021.