Female Songbirds Can Initiate the Transition from a Migratory to a Reproductive Physiology during Spring Migration
Bibliographic record
Abstract
The high energetic costs of both migration and reproduction and the physiological changes to support these costs suggest that these life-history stages should be compartmentalized with little overlap between stages. In contrast, previous studies have shown that male birds can initiate reproductive development during migration before arrival on the breeding grounds with increases in plasma testosterone levels and testis size. However, sex differences in seasonal gonadal function are now recognized as profound, and few studies to date have shown that females can initiate the costly, but critical, estrogen-dependent final stages of gonadal maturation and changes in liver function (yolk precursor synthesis, vitellogenesis) while on migration. Here, we show that female yellow warblers (Setophaga petechia) arrive on the breeding grounds with elevated plasma triglyceride levels compared with males. Some females had plasma triglyceride levels of 5–7 mmol L−1, suggesting that they arrived in a relatively advanced stage of yolk precursor production. Furthermore, we show that females that arrived with higher plasma triglyceride levels took less time to initiate their first clutch. Adaptive plasticity in the timing of the transition from a migratory to a reproductive physiology might help migrant birds buffer against a mismatch between timing of arrival and conditions on the breeding grounds and allow them to advance timing of breeding to maximize breeding productivity.
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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) | 0.002 | 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".