Biomarker of burden: Feather corticosterone reflects energetic expenditure and allostatic overload in captive waterfowl
Bibliographic record
Abstract
Abstract Allostatic load describes the interplay between energetic demand and availability and is highly context dependent, varying between seasons and life‐history stages. When energy demands exceed physiological set points modulated by glucocorticoid hormones, individuals may experience allostatic overload and transition between stages in sub‐optimal physiological states. Corticosterone, the major glucocorticoid hormone regulating energy expenditure in birds, is incorporated into growing feathers (CORTf), and it has been suggested that CORTfreflects long‐term records of allostatic load during feather growth. However, relationships between allostatic load and CORTfhave not been adequately evaluated. If such relationships exist, the use of CORTfto investigate cross‐seasonal effects could provide novel insights into impacts of past allostatic load and/or overload events. We tested whether experimental increases in daily workload during two adjacent life‐history stages would be reflected in CORTflevels, and examined if CORTflevels reflected either current energetic demand or allostatic load prior to feather growth. Daily workloads in female mallardAnas platyrhynchosducklings were increased over a 6‐week period using physical obstacles and/or carrying back‐mounted weights. We measured daily energy expenditure, growth, body mass, and CORTfin growing ducklings. Then, we induced feather moult and reapplied combinations of workload treatments for an additional 6 weeks to investigate whether effects of past energetic demands would be detected in future CORTflevels. Ducklings confronted with higher workloads during development had reduced body mass, growth rates and consequently higher daily energy expenditure and CORTfvalues compared to controls. When ducklings were fully developed, CORTfpatterns in birds re‐exposed to workload treatments reflected only current, rather than past, energetic demands. However, under allostatic overload conditions, past levels of CORTfwere positively associated with CORTfin the subsequent moult. Our study confirms the previously untested assumption that CORTfreflects energetic demand during the period of feather growth in a precocial bird. We show that allostatic overload conditions early in life, which temporarily suppress growth, can be detected using CORTf, an event potentially missed in studies which rely solely on measures of body condition alone. We suggest that CORTfcan provide a valuable biomarker of allostatic load and overload conditions during the period of feather growth, but highlight how context should be considered for studies using CORTfto investigate influences of carryover effects. Our study contributes to building a physiological foundation to inform interpretations of ecological patterns using CORTf. A plain language summary is available for this article.
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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".