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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds 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.
The global population is inferred to number 7.9 million mature individuals (Partners in Flight 2019).
The species has been undergoing a moderate decline at an average rate of 0.8% per year between 1970 and 2017 (Partners in Flight 2019). The population trend however varies locally, with some populations increasing while others are declining (Meehan et al. 2018).
Thryomanes bewickii ranges from south-west Canada through western and central U.S.A. to Mexico (del Hoyo et al. 2005). The subspecies brevicaudus and leucophrys, of Guadalupe Island (Mexico) and San Clemente Island (U.S.A.), respectively, are both now extinct (Anthony 1901, del Hoyo et al. 2005).
Text account compilers
Butchart, S. & Ekstrom, J.
BirdLife International (2022) Species factsheet: Thryomanes bewickii. Downloaded from http://www.birdlife.org on 02/12/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 02/12/2022.