Age-related differences in fall migration timing and performance of juvenile and adult Wood Thrushes departing from a breeding site
Bibliographic record
Abstract
Juvenile passerines are expected to have lower migration performance than adults due to their inexperience with long-distance flights and morphological limitations, such as shorter wing length. From 2016 to 2019 we radio-tagged nestling and adult Wood Thrushes (Hylocichla mustelina) at a breeding site in southwestern Ontario and used the automated Motus Wildlife Tracking System to test if age class predicts timing of the onset of fall migration (date, time of night), flight speed during the initial migration flight across Lake Erie, and overall pace of migration southward through the eastern United States. We detected 60/117 (51%) adults and 82/119 (69%) juveniles departing the breeding area as they initiated fall migration. Compared with adults, juveniles departed at an earlier date in fall and later time in the evening. When crossing Lake Erie on their first migratory flight juveniles travelled about 25% slower than adults but this was due primarily to adults making better use of tailwinds. When travelling south through the eastern U.S. juveniles had a slower overall migration pace (47.3 ± 5.1km/day) than adults (71.6 ± 4.7km/day). Although we found evidence that juvenile Wood Thrushes have an earlier and slower fall migration than adults, identifying the proximate and ultimate mechanisms remains a challenge. There is no evidence that juvenile Wood Thrushes are inefficient in migration flight or refueling at stopovers, and it is unlikely that the fall migration pace in this species affects their ability to compete for wintering food resources. More tracking studies from breeding sites are needed to understand the ecological factors favouring and biological significance of, age-related differences in migration performance.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| 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) | 0.000 | 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 teacher head, 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".