CRYPTIC DICHROMATISM AND SEASONAL COLOR VARIATION IN THE DIADEMED TANAGER
Bibliographic record
Abstract
We studied the patterns of sexual dichromatism and seasonal variation in plumage color in the Diademed Tanager (Stephanophorus diadematus), a species previously considered devoid of variation in adult plumage. The general coloration of this species is dark blue-violet, with a white-blue and red crown. Plumage reflectance of seven body regions from 33 study skins belonging to adults of both sexes was measured. Reflectance values were used in a principal components analysis (PCA) and hue, short-wave chroma, and UV chroma were also measured directly on the spectra. Both PCA factor scores and these latter variables were subjected to two-way ANCOVAs with sex and season as main factors and the year of capture as a covariate. We found that crowns of males were significantly brighter than those of females. In addition, the nape, chest, and belly showed significant differences in spectral shape, with relatively greater short-wave reflectance and less long-wave reflectance in males than in females. Although sexes were alike in hue, they differed in chroma in almost all body regions. Brightness also differed between seasons, and contrary to our expectation nonbreeding birds were brighter than breeding ones. This result may be a consequence of the particular molt program of tanagers that includes only a complete post-reproductive molt. Despite finding seasonal differences in spectral shape in various body regions, no significant changes in hue, short-wave chroma, or UV chroma were evident. To our knowledge, this is the first report of variation in adult plumage color for the Diademed Tanager, and we suggest that dichromatism in tanagers may be even more pervasive than is currently recognized. Dicromatismo Críptico y Variación Estacional de Color en Stephanophorus diadematus Resumen. Estudiamos los patrones de dicromatismo sexual y variación estacional en la coloración del plumaje de Stephanophorus diadematus, una especie previamente considerada carente de variación en la coloración del plumaje adulto. La coloración general de esta especie es azul violáceo oscuro, con una corona blanca azulada y roja. Se midió la reflectancia de siete regiones corporales en 33 pieles de estudio pertenecientes a adultos de ambos sexos. Los valores de reflectancia se utilizaron en un análisis de componentes principales, y además se midieron el tono (hue), la intensidad del color de onda corta y la intensidad del color de UV directamente sobre los espectros. Tanto los factores del análisis de componentes principales como las variables mencionadas fueron sujetos a ANCOVAs de dos factores, considerando el sexo y la estación como factores principales, y el año de captura como covariable. Estos análisis mostraron que la corona de los machos es significativamente más brillante que la de las hembras. Además, la nuca, el pecho y el vientre mostraron diferencias significativas en la forma espectral, presentando los machos mayor reflectancia en la zona de onda corta y menor en la zona de onda larga que las hembras. Si bien el tono no difirió entre sexos, la intensidad del color difirió en la mayoría de las regiones corporales entre machos y hembras. El brillo también difirió entre temporadas y, contrariamente a nuestra expectativa, los individuos capturados en la temporada no reproductiva fueron más brillantes que aquellos capturados en la temporada reproductiva. Este resultado podría deberse al programa de muda particular presente en Thraupidae, que incluye una única muda post-reproductiva completa. Si bien encontramos diferencias entre estaciones en la forma espectral en varias regiones corporales, no se detectaron diferencias en el tono, la intensidad del color de onda corta ni la intensidad del color de UV. Este es, de acuerdo a nuestro conocimiento, el primer estudio que muestra variación en la coloración del plumaje adulto de S. diadematus. Sugerimos que el dicromatismo en Thraupidae podría ser más común de lo que actualmente se piensa.
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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 | 0.000 |
| 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) | 0.000 | 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".