Age-specific effects on reproductive performance of grassland songbirds nesting in agricultural habitats
Bibliographic record
Abstract
Clutch size and number of young fledged has been shown to increase with female age until approximately mid-life, when reproductive performance declines. We used a long-term dataset (2002–019) to investigate age-specific effects on reproductive parameters of known-age female Savannah Sparrows (<em>Passerculus sandwichensis</em>, n = 60), and Bobolinks, (<em>Dolichonyx oryzivorus</em>, n = 75) breeding in managed hayfields and pastures in Shelburne and Hinesburg, Vermont, USA. Female Savannah Sparrows (age 1 to 6 years) showed evidence of reproductive senescence with the number of young fledged peaking at 2 years of age and declining in older age classes. Additionally, daily nest survival was strongly and negatively affected by female age. The effect of age on Bobolink reproductive performance was weak. We found an increase in the number of eggs laid from 1 to 2 years of age, no age effect on number of nest attempts or number of young fledged, and a weak, negative effect of age on daily nest survival. We found no support for an effect of grassland management treatment on daily nest survival, which may have been a result of unequal distribution of nesting attempts across treatment types. However, species-specific responses to hay harvest may have affected the relationship between age and reproductive performance. Savannah Sparrows renest rapidly and frequently after nest loss due to haying, which may constrain long-term investment in reproduction. In this highly managed system, older females may allocate less energy toward reproduction than younger females, potentially shifting those resources to behaviors that support annual survival. By contrast, Bobolinks may not invest as heavily in reproduction, generally renesting only once after nest failure and have a truncated breeding season because of their long fall migration to South America. Consequently, their reproductive success may not vary as strongly with age.
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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".