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 may be small, but it is not believed to 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 overall population trend is increasing, although some populations may be stable and others have unknown trends (Wetlands International 2006). This species has undergone a large and statistically significant increase over the last 40 years in North America (132% increase over 40 years, equating to a 23.4% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).
Text account compilers
Butchart, S. & Ekstrom, J.
BirdLife International (2020) Species factsheet: Ardea herodias. Downloaded from http://www.birdlife.org on 21/01/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/01/2020.