Cuckoos do not select redstart hosts of better quality despite potential growth consequences for nestlings
Bibliographic record
Abstract
Common cuckoo, Cuculus canorus , females rely on host species to raise their young and therefore should benefit from targeting high-quality individuals that maximize their fitness. Empirical evidence for individual host selection is, however, mixed with some studies suggesting random choice. Nevertheless, it is possible that the lack of consistent evidence for host selection may be because spatio-temporal variation in host availability has rarely been accounted for, or because the implications of host choice on fitness outcomes have not been tested experimentally. Here, we combined long-term monitoring data with an experiment to examine whether cuckoo females parasitising common redstarts, Phoenicurus phoenicurus , target individual hosts of higher quality to optimize their nestlings' growth. We first explored the scope for cuckoos to choose, finding spatial and temporal variation in host nest availability and host quality (using completed clutch size as a proxy). Cuckoos may choose hosts at different spatial scales (i.e. near neighbours versus habitat patches), so we next investigated whether parasitism varied with host quality (1) across the study area and (2) among nests within putative breeding areas. However, we found no evidence that redstarts laying larger clutches were more likely to be parasitized. Finally, we conducted a crossfostering experiment to disrupt the cuckoo's choice of nest. Moving cuckoo eggs to nonparasitized nests and between parasitized nests had no effect on morphometric growth of nestlings (mass, tarsus and wing length). Nestlings raised by foster parents differing in quality (i.e. smaller/larger clutch size) from the original nest tended to grow faster but smaller in asymptotic mass and tarsus length. Together these results suggest that the potential fitness benefits of choosing high-quality hosts do not compensate possible costs of searching for hosts in this system, although using different proxies for individual quality could help resolve the complexities inherent to host choice.
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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) | 0.001 | 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".