Evolution of Clutch Size in Cavity‐Excavating Birds: The Nest Site Limitation Hypothesis Revisited
Bibliographic record
Abstract
There are two major competing hypotheses for variation in clutch size among cavity‐nesting species. The nest site limitation hypothesis postulates that nesting opportunities are more limited for weak excavators, which consequently invest more in each breeding attempt by laying larger clutches. Alternatively, clutch size may be determined by diet; the clutch sizes of strong excavators may be smaller because they are able to specialize on a more seasonally stable prey. We built a conceptual model that integrated hypotheses for interspecific variation in clutch size and tested it with comparative data on life‐history traits of woodpeckers (Picidae) and nuthatches (Sittidae). In most analyses, diet explained more variation in clutch size among species than did propensity to excavate. Migratory status was positively associated with clutch size but was difficult to distinguish from diet since resident species consumed more bark beetles (a prey available in winter) and had smaller clutches than migratory species. The literature suggests that cavities are not limited in natural, old‐growth forests. Although our data do not rule out nest site limitation, we conclude that annual stability of food resources has a larger impact on the evolution of clutch sizes in excavators than does limitation of nest sites.
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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 | 0.001 |
| Science and technology studies | 0.000 | 0.001 |
| 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".