Can endocranial volume be used as an estimate of brain size in birds?
Bibliographic record
Abstract
Endocranial volumes of vertebrate skulls and brain masses are often used interchangeably in comparative analyses of brain size. We test whether endocranial volume can be used as a reliable estimate of brain size in birds by comparing endocranial volumes with brain masses across 82 species using absolute values and with respect to body size. The results of paired tests across all 82 species and within two orders, Passeriformes and Psittaciformes, did not yield a significant difference between the two measures. These results were supported by correlational analyses that showed a significant positive relationship between endocranial volume and brain mass. Unpaired tests within short-tailed shearwaters (Puffinus tenuirostris) and paired tests within budgerigars (Melopsittacus undulatus) also yielded no significant differences between endocranial volume and brain mass. Thus, a combination of interspecific and intraspecific comparisons indicates that endocranial volume does provide a reliable estimate of brain size. Although this may enable more rapid collection of avian brain size data, endocranial volume should be used with caution because it cannot account for seasonal and age-related variation and cannot be used to measure differences in brain structure.
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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 | 0.002 | 0.013 |
| Meta-epidemiology (narrow) | 0.001 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.003 | 0.002 |
| Science and technology studies | 0.000 | 0.001 |
| Scholarly communication | 0.001 | 0.002 |
| Open science | 0.001 | 0.001 |
| Research integrity | 0.001 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.001 |
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".