Length of hackle iridescence increases with age in European Starlings ( <i>Sturnus vulgaris</i> )
Bibliographic record
Abstract
Bird ornaments, such as plumage and song, can reflect the age of individuals. Knowledge of an individual's age and potential past breeding experience is important to future mates and to scientists studying mate-choice decisions, levels of parental investment, and reproductive performance. The iridescent length of hackles (throat feathers) has been used to sex and age adult European Starlings (Sturnus vulgaris). We confirmed that males have longer portions of hackle iridescence and overall longer hackles than females. Although After Second Year (ASY) adults have longer hackle iridescence than Second Year (SY) adults, only two other studies that we know of have examined the iridescent length of hackles in the same individuals over time. We measured hackle iridescent length of returning adults over 8 years, and discovered that it continues to increase with age in both females (25/26) and males (21/21). It had the greatest increase over the 1-year period when breeding adults switched from the SY to the ASY age category. Total hackle length also continued to increase with age, albeit more reliably for males (18/21) than females (13/26). These results demonstrate that hackle iridescence is a potential signal of age throughout the lifespan of a European Starling.
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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 | 0.000 | 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".