Tracing salmon nutrients in riparian food webs: isotopic evidence in a ground-foraging passerine
Bibliographic record
Abstract
The predictable annual spawning of anadromous salmon (genus Oncorhynchus Suckley, 1861) provides an important marine resource subsidy to terrestrial species throughout the North Pacific. Using isotopic ratios of nitrogen (δ15N) and carbon (δ13C), we examine pathways of salmon nutrient uptake by a ground-foraging passerine, the winter wren ( Troglodytes troglodytes (L., 1758)), captured above and below waterfall barriers to salmon migration from two rivers on the central coast of British Columbia. Wren feathers exhibited substantial variation in δ15N (range = 18.6‰) and δ13C (range =7.9‰), approximating the isotopic range of invertebrates sampled at our study sites. Mean δ15N values of feathers and feces representing the fall diet of winter wrens were enriched by 4.8‰ and 8.0‰, respectively, below versus above the waterfall barriers. We observed positive relationships between δ15N and δ13C in fall-grown feathers and fecal samples below the falls but not above the falls, and large positive shifts (as high as 14.3‰) in15N from summer to fall within individual birds. The large isotopic variation observed in this system likely can be explained by the mobility of wrens, isotopic variation in their prey, and individual variation in the consumption of fly larvae from salmon carcasses. Our results identify both direct and indirect pathways by which salmon-derived nutrients are cycled into top-level consumers.
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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 | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 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) | 0.000 | 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".