Experimental effects of early‐life corticosterone on the hypothalamic–pituitary–adrenal axis and pre‐migratory behaviour in a wild songbird
Bibliographic record
Abstract
Summary Although laboratory studies have shown that chronic exposure to elevated glucocorticoids during development can have profound effects on the physiology and behaviour of animals, we still have a poor understanding of the proximate and ultimate consequences of early life stress on individuals in the wild. In an island population of Savannah sparrows (Passerculus sandwichensis), we examined multiple hypotheses to explain how elevated glucocorticoid exposure during the nestling period influenced both hypothalamic–pituitary–adrenal (HPA) axis function during the nestling period and the subsequent movement and survival of young after they fledged the nest. We exposed nestlings to exogenous corticosterone from 2 to 6 days of age and then measured both baseline and stress‐induced (30‐min restraint) plasma corticosterone levels prior to fledging (day 7). We then recaptured young throughout the pre‐migratory period and used mark–recapture analysis to estimate temporary emigration from the capture site (movement) and survival. Corticosterone‐treated nestlings had higher baseline corticosterone levels and lower stress reactivity than untreated individuals, and were more sensitive to inclement weather. Although there was no evidence that corticosterone treatments influenced survival, treated individuals had higher rates of temporary emigration outside of the study site than sham or controls. Our results provide support for the ceiling hypothesis, which suggests that individuals with chronic elevated glucocorticoids can lead to a dampened HPA axis response. We also provide support for the CORT‐activity hypothesis, which suggests that elevated glucocorticoids can increase activity levels, at least 1–2 months after leaving the nest. Our study highlights the importance of tracking individuals across multiple stages of the annual cycle to understand how early life events carry over to influence both physiology and behaviour.
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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 | 0.001 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.001 | 0.002 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.001 | 0.002 |
| Insufficient payload (model declined to judge) | 0.002 | 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".