Size‐Related Advantages for Reproduction in a Slightly Dimorphic Raptor: Opposite Trends between the Sexes
Bibliographic record
Abstract
Abstract Despite many comparative analyses and more than 20 proposed hypotheses, there is still little consensus over the factors promoting the evolution of reversed sexual dimorphism (RSD) in raptorial species. Furthermore, intrapopulation studies, which may elucidate how RSD is maintained once evolved, have been surprisingly scarce and only focused on a handful of species with medium to high dimorphism. We examined the reproductive advantages associated with body size and condition, measured in the pre‐laying period, in a diurnal raptor with low sexual dimorphism, the black kite (Milvus migrans). The study population was essentially monomorphic in size. For females, there was an evidence of reproductive benefits associated with larger size and/or with better body condition. Larger females had also access to higher quality partners and territories, consistent with the ‘intrasexual selection’ hypothesis, by which members of the larger sex enjoy size‐related advantages in intrasexual competition over a scarce resource, the smaller sex. Opposite trends emerged for males: smaller, leaner males had higher breeding output, consistent with the ‘small efficient male’ hypothesis. Overall, the fact that we observed in an essentially monomorphic population the same selection pressures previously found in species with marked dimorphism suggests that such reproductive advantages may be counterbalanced in our study model by opposite selection pressures during other stages of the life cycle. This casts some doubts on the evolutionary significance of studies focusing exclusively on reproduction and calls for the need of more comprehensive analyses incorporating trait‐mediated differentials in survival and recruitment.
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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) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 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) | 0.003 | 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".