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 is inferred to be stable, and so it does not approach the threshold 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 is estimated to number 120,000-130,000 individuals (Wetlands International 2018). This roughly equates to 80,000-90,000 mature individuals.
Data from the North American Breeding Bird Survey, combined for Aechmophorus occidentalis and A. clarkii, implies that the species has undergone a non-significant increase over the past three generations (24 years) (Sauer et al. 2017); whereas in Wetlands International (2018) the population trend is unknown. Given the uncertainty, and the fact that trend data is for these two species combined, the species is tentatively placed here as stable.
Text account compilers
Butchart, S., Westrip, J., Ekstrom, J.
BirdLife International (2023) Species factsheet: Aechmophorus occidentalis. Downloaded from http://datazone.birdlife.org/species/factsheet/western-grebe-aechmophorus-occidentalis on 29/11/2023.
Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from http://datazone.birdlife.org on 29/11/2023.