Bird migration on the edge: Experimental manipulation of corticosterone advances departure dates
Bibliographic record
Abstract
Endogenous reserves accumulated during migration stopovers help most migratory birds cope with environmental uncertainties and fuel energy demands associated with migration and/or reproduction. Migratory decisions, such as departure time, should thus be finely tuned to energy intake rate at stopover sites. However, the physiological drivers of these decisions remain poorly understood. Glucocorticoids such as corticosterone (CORT) are known to mediate the stress response in birds but also play a key role in the regulation of energy intake and behavior, particularly during demanding life-history stages. We investigated how baseline CORT influences bird energy acquisition and migratory decisions by manipulating the physiology of wild snow geese (Anser caerulescens atlanticus) through subcutaneous implantation of corticosterone pellets during spring stopover. Birds of similar body condition were paired, implanted with CORT or placebo pellets, and tracked with GPS-GSM collars and accelerometers to monitor foraging efforts, habitat use, and migration departure date. We measured foraging rates from accelerometer data and classified using an unsupervised algorithm calibrated with field video recordings. CORT-treated birds foraged 20% more on average than placebo individuals over 10 days, primarily by increasing foraging efforts rather than altering habitat use. Most of the difference occurred in the first days post-implantation (Foraging rates on Day 2, CORT: 0.4 [95% CI: 0.34, 0.47]; placebo: 0.3 [0.2, 0.36]) and gradually faded to zero afterward (Foraging rates on Day 10, CORT: 0.26 [0.21, 0.32]; placebo: 0.26 [0.21, 0.31]). These higher foraging rates advanced the median departure date of CORT-treated individuals by 2 days compared to placebo (median departure: CORT, May 17 [15, 17]; placebo, May 19 [17, 20]). Our experimental manipulation is one of the first to induce a positive shift in migration phenology and confirms the role of CORT baseline levels in modulating energy acquisition and migratory decisions in a wild bird species.
Fetched live from OpenAlex and de-inverted. Abstracts are not stored in this database: the inverted indexes are 8.6 GB of the frame’s 9.3 GB of text, and the host has 13 GB free.
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 | 0.001 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| 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".