Different colors reveal different information: how nutritional stress affects the expression of melanin- and structurally based ornamental plumage
Bibliographic record
Abstract
Avian plumage colors have emerged recently as model systems for investigating the types of information that can be signaled by showy sexual displays in animals. In many species, the brightness of carotenoid-based plumage reflects the health and condition of individuals and is used in mate selection. The information contained in melanin-based and structurally based ornamental colors in birds is less well resolved, however. We subjected male house sparrows Passer domesticus and brown-headed cowbirds Molothrus ater to stressful nutritional conditions during molt to test the hypothesis that melanin- and structurally based plumage colors are nutritionally condition-dependent. We restricted food access for treatment males during randomized 6 h periods on 4 days per week, while allowing control birds access to food ad libitum throughout the course of the molt. We found that the size and brightness of the melanin-based throat badges in male house sparrows were not affected by nutritional stress. Similarly, there were no differences between treatment and control male cowbirds in the size or brightness of the melanin-based brown hood. However, the structurally based iridescent plumage of cowbirds was indicative of the nutritional condition of males during molt. Nutritionally stressed cowbirds grew significantly less colorful plumage than did males with access to food ad libitum. These results are consistent with observations in other avian species that different types of plumage color communicate different sets of information. Melanin ornaments are less sensitive to nutritional conditions during molt and instead may reflect the hormonal status and/or competitive ability of males, whereas structural coloration appears to be an accurate signal of health and condition.
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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) | 0.001 | 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".