LC
Brewer's Sparrow Spizella breweri



Justification

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.

Population justification
The global population is estimated to number 17 million mature individuals (Partners in Flight 2019).

Trend justification
The species has been undergoing a moderate decline at an average rate of 1.1% per year between 1970 and 2017 (Partners in Flight 2019). Short-term trends suggest that the population has declined by 21% over the past ten years (Pardieck et al. 2018). However, population size estimates fluctuate between years and the trend estimate is biased towards end point values; therefore it is here assumed that the overall rate of decline does not approach the threshold for Vulnerable.

Distribution and population

This species is found in Canada, the U.S.A. and Mexico. The nominate subspecies breweri occurs in the arid intermountain west of the U.S.A. (stretching north into south-east Alberta and south-west Saskatchewan, Canada) (Byers et al. 1995; Rotenberry et al. 1999). Further north, it is replaced by subspecies taverneri (Byers et al. 1995; Rotenberry et al. 1999), whose range extends into south-eastern Alaska.

Ecology

Brewer's Sparrow breeds on sagebrush flats and other open scrubby areas. It winters from just south of the breeding range in south-western USA to central Mexico (Byers et al. 1995, Rotenberry et al. 1999), though the wintering grounds of subspecies taverneri remain largely unknown.

Threats

Habitat loss has accelerated owing to the invasion of exotic plants, particularly Cheatgrass Bromus tectorum, which has increased fire frequency and altered post-fire successional pathways (Rotenberry 1998).

Acknowledgements

Text account compilers
Hermes, C.

Contributors
Bird, J., Butchart, S., Harding, M. & Mahood, S.


Recommended citation
BirdLife International (2022) Species factsheet: Spizella breweri. Downloaded from http://www.birdlife.org on 03/07/2022. Recommended citation for factsheets for more than one species: BirdLife International (2022) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 03/07/2022.