Field research guided by citizen science and monitoring data reveal a novel alpine breeding distribution and vegetation associations of a declining, habitat-specialist songbird in Colorado, USA
Bibliographic record
Abstract
Documenting the breeding habitat and distribution of migratory songbirds is essential for accurately assessing their conservation status. The “sagebrush” subspecies of the Brewer’s Sparrow (Spizella breweri breweri) breeds in greatest abundance in sagebrush-dominated (Artemisia spp.) shrublands of western North America, and the “timberline” subspecies (S. b. taverneri) breeds in shrubs or krummholz at or above the tree line in mountain ranges from Alaska to Montana. Brewer’s Sparrows have also been reported at alpine sites in summer in mountain ranges across the western United States, but their taxonomic affiliation and breeding status are unknown. We reviewed monitoring, citizen science, and specimen data for Colorado and identified 186 historical summer observations of Brewer’s Sparrows at 59 alpine sites (3334–4288 m elevation). We surveyed 39 alpine sites in June–July 2021–2023, detected a total of 100 adults (mostly singing males) at 26 alpine sites (3395–3754 m elevation), and confirmed breeding at three sites. Males occupied mixed-species willow patches 0.9–1.8 m tall, often intermixed with sparse conifer krummholz. We recorded songs and captured, measured, photographed, and collected blood and feather samples from birds at a subset of alpine sites and nearby, lower-elevation sagebrush sites in May–July 2021. Vegetation associations and timing of breeding at alpine sites closely matched those of taverneri, but short songs, external morphology, coloration, and genetics of alpine birds overlapped with sagebrush birds and more closely matched those of range-wide breweri. Our results indicate that western Colorado supports a widely-distributed, but poorly-documented, population of alpine breweri breeding in willows with sparse conifer krummholz within a relatively narrow elevation band at or above the tree line. Whether alpine birds are itinerant breeders that first nested in sagebrush remains unknown. Our results complicate interpretation of differences in breeding habitat and breeding phenology as supporting criteria for subspecific identification and taxonomic delineation in this species.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".