Diego Ocampo

Introduction: The taxonomy of Galliformes species, a group closely associated with humans since antiquity, remains unclear at various taxonomic levels, producing taxonomic changes constantly. Objective: Our objective is to provide morphological and acoustic data to support the recent taxonomic recognition of Colinus leucopogon (Spot-bellied Bobwhite) as a distinct species from Colinus cristatus (Crested Bobwhite). Methods: Using a combination of morphological and acoustic analyses, we assessed the differences between these two recently recognized species and compared them with the two other well-established species within the genus: C. nigrogularis (Black-throated Bobwhite) and C. virginianus (Northern Bobwhite). Results: Our acoustic analysis of male songs from 64 individuals showed significant differences in maximum amplitude frequency, song duration, and number of elements, which can act as a reproductive barrier between C. cristatus and C. leucopogon. Morphological analyses, however, revealed only limited differences, primarily in tarsus length and wing chord length. Conclusions: Our findings suggest that while male song characteristics strongly support the recognition of C. cristatus and C. leucopogon as distinct species, morphological differences are less pronounced, potentially due to ecological factors such as habitat similarity and altitudinal distribution. This study highlights the importance of including both acoustic and morphological traits in resolving taxonomic uncertainties and understanding species boundaries in Galliformes.

Introduction: Natural history collections play a vital role in research and education. However, their value and benefits are frequently overlooked, and the museum’s holdings tend to be unknown outside of museum personnel. Objective: We aim to evaluate and report the taxonomic and geographic coverage of the ornithological collections of the museum of zoology at the Universidad de Costa Rica (MZUCR). Methods: We estimated species-level and family-level representation across the six sub-collections of the collection of ornithology at MZUCR, and contrasted the taxonomic coverage and temporal patterns of the round-skin collection against other collections of Costa Rican birds housed in Costa Rica and abroad. Results: The eggs and nests collection represent only a small fraction of the Costa Rican breeding birds (569 nests from 128 species and 117 egg clutches from 78 species). The skeleton collection is the smallest with little growth over time (353 skeletons from 203 species). Tongues collection is growing (845 tongues from 329 species) and expected to fuel future research in comparative morphology. The tissue collection is the most recent and has the highest growth rate (1979 samples from 408 species), reflecting the importance of molecular studies in current research. The round-skin collection has the highest representation of the Costa Rican avifauna (5080 skins from 761 species), but it represents a small fraction of all the specimens collected in Costa Rica. Conclusion: These results highlight the importance of the MZUCR collection in documenting the Costa Rican avifauna, and its potential for ornithological research. However, the majority of species do not have the sufficient number of specimens required for robust population level studies. We underscore the importance of continuous growth and proper management of scientific collections for their use for future generations.

After establishing secondary contact, recently diverged populations may remain reproductively isolated or may hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the variable seedeater (Sporophila corvina) to examine how coloration and genetic divergence shape patterns of hybridization. We found that differences in plumage coloration are probably maintained by divergent selection across contact zones; however, the degree of plumage differentiation does not match overall patterns of hybridization. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage), populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later‐generation hybrids, suggesting frequent reproduction and high survivorship for hybrid individuals. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic structure between populations. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow.

Because studies of plumage coloration often focus on highly elaborate and conspicuous males, little is known about the factors driving the evolution of drab plumage in females of dichromatic species. We explored variation in the color properties of drab female plumage across subspecies of the Variable Seedeater (Sporophila corvina), and found a correlation between plumage brightness of male and female plumage patches. This correlation is consistent with the hypothesis that differences in plumage brightness among females result, at least partially, from a genetic correlation or shared developmental pathway with the more conspicuous male plumage traits that are shaped by sexual selection. Further, we modeled the perception of female plumage using the avian visual system and found that most of the variation in color among females is mostly undetectable by birds; therefore, it is unlikely for such variation to have evolved via direct sexual selection as a signal for recognition or assortative mating. Together, these results suggest that variation in S. corvina female color result from non-adaptive processes. However, we found a reduced variation on color of dorsal patches compared with that of ventral patches among females, which could be explained by natural selection operation on crypsis, reducing the variation on dorsal patches. Finally, we found little differences in plumage color between adult females and juveniles, which suggest selection for juveniles to resemble adult females possibly to reduce aggression from adult males. Additional within-population studies and behavioral experiments are needed to discern the evolutionary factors driving variation on S. corvina female color and its function.

After establishing secondary contact, recently diverged populations may remain reproductively isolated or hybridize to a varying extent depending on factors such as hybrid fitness and the strength of assortative mating. Replicated contact zones between hybridizing taxa offer a unique opportunity to explore how different factors interact to shape patterns of hybridization. Here, we used genomic and phenotypic data from three independent contact zones between subspecies of the Variable Seedeater (Sporophila corvina), to examine how coloration and genetic divergence shape patterns of hybridization. We found that plumage coloration has limited introgression across contact zones, but the degree of plumage divergence does not explain overall patterns of introgression. Across two parallel contact zones between populations with divergent phenotypes (entirely black vs. pied plumage) populations hybridized extensively across one contact zone but not the other, suggesting that plumage divergence is not sufficient to maintain reproductive isolation. Where subspecies hybridized, hybrid zones were wide and formed by later-generation hybrids, suggesting that hybrids present similar or higher fitness than parental subspecies. Moreover, contemporary gene flow has played an important role in shaping patterns of genetic diversity between populations. Overall, our results demonstrate that divergence in plumage coloration is important in reducing gene flow but insufficient in maintaining reproductive isolation in this clade, and that other factors such as divergence in song and time since secondary contact may also play an important role in driving patterns of reduced hybridization and gene flow.

Plumage coloration largely depends on the type and concentration of pigments present in feathers. Therefore, changes in pigment deposition may result in aberrant colorations, which, in turn, will likely interfere with the plumage color’s function (e.g., signaling, protection). Published records of aberrant plumage colors underestimate the type and frequency of these phenotypes, especially in the tropics. Here, we report five independent observations of phaeomelanic males of the Variable Seedeater (Sporophila corvina), in which typically white feathers were instead chestnut-red, likely due to the deposition of phaeomelanin. Our observations add to previous reports of aberrant melanin-based coloration in this species, suggesting that genomic region(s) influencing the expression of phaeomelanin are a biased target for mutations. Because mutations affecting the regulation of melanin deposition result in novel plumage phenotypes, we discuss aberrant phenotypes as an important source of variation fueling rapid divergence among populations of this avian clade.

The ratio of brain size to body size (relative brain size) is often used as a measure of relative investment in the brain in ecological and evolutionary studies on a wide range of animal groups. In birds, a variety of methods have been used to measure the brain size part of this ratio, including endocranial volume, fixed brain mass, and fresh brain mass. It is still unclear, however, whether these methods yield the same results. Using data obtained from fresh corpses and from published sources, this study shows that endocranial volume, mass of fixed brain tissue, and fresh mass provide equivalent estimations of brain size for 48 bird families, in 19 orders. We found, however, that the various methods yield significantly different brain size estimates for hummingbirds (Trochilidae). For hummingbirds, fixed brain mass tends to underestimate brain size due to reduced tissue density, whereas endocranial volume overestimates brain size because it includes a larger volume than that occupied by the brain.

Los factores biomecánicos, el comportamiento e historia natural de las especies pueden influenciar la forma y dimensión del ala en las aves. Por lo tanto, la morfología de las alas de cada especie podría estar adaptada al ambiente en el que habitan. En palomas (familia Columbidae) existe un gradiente de especies que tienden a volar mucho y otras que vuelan muy poco. El objetivo de esta investigación es determinar si la forma de las alas de seis especies de palomas se asocia con su capacidad de vuelo. Predecimos que las especies Patagioenas flavirostris y P. nigrirostris que tienden a volar largas distancias presentan alas relativamente largas y puntiagudas; mientras que Geotrygon montana que se desplaza principalmente caminando presenta alas relativamente anchas y redondeadas. Especies con capacidad de vuelo intermedio (Leptotila verreauxi, L. cassini y Zenaida asiatica) van a presentar alas con características intermedias. Estimamos la carga alar, proporción de la forma, conicidad alar, largo relativo y el área alar promedio para cada especie. Realizamos un análisis discriminante para determinar cuál combinación de variables explica mejor la diferencia morfológica de las alas entre las seis especies y probamos que tan robusto es este modelo mediante una prueba binomial. El modelo clasificó correctamente el 57 % de los individuos en su propia especie. Por lo tanto, encontramos que el tipo de desplazamiento predominante en cada una de las seis especies de Columbidae analizadas, se asocia con la morfología alar: alas adaptadas para vuelos en zonas abiertas en P. flavirostris y P. nigrirostris, alas adaptadas para vuelos muy maniobrables en hábitats densos en G. montana, y alas con características intermedias en L. verreauxi, L. cassini y Z. asiatica.