Southward and downslope extensions of breeding ranges of birds in southern California
Bibliographic record
Abstract
Range changes that appear contrary to predictions based on climate warming deserve examination for any shared factors opposing the general trend. Of the ~273 species of native birds currently or historically nesting regularly in southern California, there is, in the historic record, some level of evidence for a southward or downslope range extension in 52. A few apparent extensions may be illusory, based on more thorough exploration since the mid-20th century, but the great majority represent actual changes. These range from minor, involving only a few pairs at a few localized sites, to extensive, as in the cases of the Western Grebe (Aechmophorus occidentalis), Pacific-slope Flycatcher (Empidonax difficilis), American Crow (Corvus brachyrhynchos), Western Bluebird (Sialia mexicana), American Robin (Turdus migratorius), and Orange-crowned Warbler (Oreothlypis celata). Some expansions began as early as the 1930s (American Robin, Orange-crowned Warbler), whereas others, such as that of the Canada Goose (Branta canadensis), have gained momentum only in the 21st century. Roughly half of the species with expanding ranges are associated with coniferous forest or other montane habitats. Some of these expansions may be associated with the increasing density of California’s forests where not burned or logged, but others are by montane species that use shrubby habitats or open forest. Eighteen of the species with expanding ranges are associated with water, capitalizing on the many reservoirs, sewage ponds, and other water bodies created for importation, management, and control of water in southern California. Ten species exploit the urban habitat that now pervades southern California, but most of these have spread in natural or lightly modified habitat as well. We conclude that habitat modifications have been a leading force driving southward and downslope range expansions of birds in southern California.
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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 | 0.001 | 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".