Functional morphology as a barrier to the evolution of grasp-ejection in hosts of the Brown-headed Cowbird (<i>Molothrus ater</i>)
Bibliographic record
Abstract
Acceptance of eggs of the Brown-headed Cowbird ( Molothrus ater (Boddaert, 1783)) by hosts is enigmatic because hosts usually raise fewer of their own young when parasitized. Ejection may not be adaptive for small hosts because they cannot eject cowbird eggs efficiently. Grasp-ejection apparently has a negligible cost but requires a bill of a minimum length that is not known. In this study, we examined the limits of grasp-ejection of the American Robin ( Turdus migratorius L., 1766) and the Gray Catbird ( Dumetella carolinensis (L., 1766)). We determined the largest object width that each species is capable of grasping (limit width) by observing individuals grasping models larger than cowbird eggs in 104 video-recorded ejections and one direct observation. We standardized the limit width to the tomial length of each species (limit ratio) and extrapolated to the width of a cowbird egg to predict the minimum tomial length required for grasp-ejection. Our results suggest that the minimum tomial length required to grasp-eject a cowbird egg is 15.9–16.1 mm and the probability of host-egg damage during grasp-ejection does not increase as the limit ratio increases. Bill length may prevent the evolution of grasp-ejection in cowbird hosts with bills shorter than 16 mm.
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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 | 0.001 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 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".