Origins of irruptive migrations by Common Crossbills <i>Loxia curvirostra</i> into northwestern Europe revealed by stable isotope analysis
Bibliographic record
Abstract
We used analyses of stable hydrogen isotope (δ2H) measurements in Common Crossbill feathers (δ2Hf) to infer the region of origin of Crossbills collected from different irruptions into Britain, Iceland and the Faeroes, comparing these values with those from birds sampled in breeding areas in Britain and elsewhere in the western Palaearctic. No differences in δ2Hf values were found between different species or sexes of Crossbills that could be presumed to have grown their feathers in the same region, but juveniles had lower δ2Hf values than adults that had grown their feathers in the same region. On the basis mainly of museum skins, immigrant birds were sampled from 30 different irruption years, spanning the period 1866–2009, with annual samples varying from one to 29 individuals. The variation in δ2Hf values within irruptions was substantially less than the variation between irruptions, indicating that irruptions in different years originated in different parts of the western Palaearctic boreal zone. Birds with lower δ2Hf values tended to arrive later in the migration season, which was consistent with the idea that they had travelled further. In 17 of the irruption years, the birds had mean δ2Hf values more than −120‰, suggesting that they had originated somewhere in the region extending from northern Scandinavia to northwestern Russia. In these years the birds arrived early, in June and July. In 10 of the irruption years, the mean δ2Hf values were between −120 and −130‰, suggesting origins further east, in northern Russia, east of Archangel (about 40°E). In only three of the 30 years (1898, 2002, 2009) the mean δ2Hf values were even lower (< 130‰), and these birds arrived in late July, August and September. Birds in these three irruptions had probably come from Siberia, east of the Ural Mountains. In at least three irruption years (1898, 1927, 1985) the observed range of δ2Hf values suggested that birds had come from more than one of these regions, including east of the Urals in 1898 and 1927.
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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 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| 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".