Lesser Scaup Aythya affinis


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 tentatively assessed to be stable, hence the species does not approach the threshold for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely 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.

Population justification
The global population is estimated to number 3,700,000 mature individuals and is currently stable (Meehan et al. 2018, Pardieck et al. 2018, Partners in Flight 2020).

Trend justification
The species is considered to have undergone a historical decline (Partners in Flight 2020, Wetlands International 2020), but recent North American Breeding Bird Survey and Christmas Bird Count data appears to show that the species has been roughly stable in the short-term (Meehan et al. 2018, Pardieck et al. 2018). Therefore, the species is assessed here as being stable.


Text account compilers
Hermes, C.

Butchart, S., Ekstrom, J. & Westrip, J.R.S.

Recommended citation
BirdLife International (2023) Species factsheet: Aythya affinis. Downloaded from on 31/03/2023. Recommended citation for factsheets for more than one species: BirdLife International (2023) IUCN Red List for birds. Downloaded from on 31/03/2023.