Ornithology

Abstract Geographic and gender biases in the history of ornithology have led to missed opportunities, and in some cases, backwards understanding of key evolutionary and behavioral processes. In studies of elaborate coloration and song, female birds have historically been neglected. The main framework for thinking about the evolution of elaborate traits has been sexual selection, whereby competition for mates has led to elaborate coloration and long, complex songs in males. Females have often been ignored or assumed not to change. Here we review current understanding of how these elaborate traits have evolved in temperate versus tropical areas. Ongoing research on orioles, other blackbirds, and all songbirds indicates that female song is much more common than previously thought. Social selection acting on both females and males throughout the year likely played an important role in the original evolution of bird song in both sexes. In many cases, the evolution of sexual dimorphism in both coloration and song is driven by the loss of elaboration in females, rather than the gain of elaboration in males. Accounting for both male and female display traits will lead to a clearer understanding of the evolution of coloration and song, which will also facilitate a more comprehensive understanding of the full scope of topics in avian ecology, evolution, behavior, and conservation.

North American bee-clade hummingbirds (Mellisugini) frequently enter torpor during autumn migrations to save energy. The frequency with which they use torpor is mediated by lipid (fat) loads. To estimate frequencies and temporal patterns of torpor use, we measured fat loads and feather hydrogen stable isotope ratios (delta 2H) in 942 individuals of 4 species of migrating bee hummingbirds: Selasphorus rufus (Rufous Hummingbird), S. calliope (Calliope Hummingbird), S. platycercus (Broad-tailed Hummingbird), and Archilochus alexandri (Black-chinned Hummingbird), at a stopover site in Southwestern New Mexico. In a subsample of 63 juveniles across the 4 species, we constructed predictive functions relating fat loads and feather delta 2H to torpor incidence, using direct measurements of torpor use via respirometry. We used these functions, along with fat and delta 2H data from the remaining 563 captured juvenile birds, to estimate their temporal patterns of torpor use. Fat loads were significantly higher in adult S. rufus and S. platycercus than in juveniles, but did not differ with age in S. calliope and A. alexandri. In S. rufus, fat loads decreased with capture date, whereas in A. alexandri they increased. We found no effect of capture date on fat loads in S. platycercus and S. calliope. In all species, torpor incidence decreased with increasing fat in a predictable fashion. A large fraction (70%) of S. calliope and a smaller fraction (30%) of S. rufus individuals entered torpor, but these fractions remained constant over time. In contrast, the fraction of S. platycercus individuals entering torpor increased with capture date, whereas that of A. alexandri decreased. Our results revealed similarities and unexpected interspecific differences in fat loads and torpor incidence in migratory bee-clade hummingbirds. Some of these differences are likely the result of dissimilar migration strategies. Others remain unexplained but represent an opportunity to better understand the causes and consequences of torpor-mediated migration. We measured body fat loads and nocturnal torpor use in four species of migrating hummingbirds-Selasphorus rufus (Rufous Hummingbird), S. calliope (Calliope Hummingbird), S. platycercus (Broad-tailed Hummingbird), and Archilochus alexandri (Black-chinned Hummingbird)-to determine how they are influenced by migration timing and distance at a stopover site in southwestern New Mexico, USA. We used quantitative magnetic resonance to measure body fat, respirometry to measure torpor incidence, and feather hydrogen stable isotope ratios to infer migration distance. We predicted that juvenile birds flying longer distances would carry less fat, would be more likely to enter torpor, and that the interplay between fat and migration distance would vary with migration strategy. In all species, lower body fat loads increased torpor use; however, torpor probability varied among species, with longer-distance migrants having constant torpor frequencies over time, and medium-distance migrants showing opposite trends over time. Our results suggested that migrating hummingbirds of different species use diverse energy management strategies, according to migration timing and distance. Para ahorrar energ & iacute;a, los colibr & iacute;es migratorios Norteamericanos del clado abeja (Mellisugini) frecuentemente entran en torpor/letargo durante la migraci & oacute;n oto & ntilde;al. La frecuencia con la que usan torpor es mediada por las cargas de l & iacute;pidos. Con el objeto de estimar los patrones temporales de uso de torpor medimos cargas de grasa y composici & oacute;n de isotopos de hidr & oacute;geno (delta 2H) en 942 individuos de cuatro especies de colibr & iacute;es abejas migratorios: Selasphorus rufus (colibr & iacute; rufo), S. calliope (colibr & iacute; caliope), S. platycercus (colibr & iacute; de cola ancha), and Archilochus alexandri (colibr & iacute; gorjinegro), en un sitio de escala en el Sudoeste de Nuevo M & eacute;xico. En una sub-muestra de 63 juveniles construimos funciones para predecir la incidencia de torpor como funci & oacute;n de las cargas de l & iacute;pidos y valores de delta 2H usando medidas directas de torpor via respirometr & iacute;a. Usamos estas funciones junto con cargas de grasa y delta 2H medidas en los 563 colibr & iacute;es restantes para estimar patrones temporales de uso de torpor. Las cargas de grasa fueron significativamente m & aacute;s altas en adultos de S. rufus y S. platycercus que en juveniles, pero no difirieron con la edad en S. calliope and A. alexandri. En S. rufus las cargas de grasa decrecieron con fecha de captura, mientras que en A. alexandri aumentaron. No encontramos efectos de tiempo en las cargas de grasa de S. platycercus o S. calliope. En todas las especies la incidencia de torpor decreci & oacute; con las cargas de grasa de un modo predecible. Una fracci & oacute;n muy alta (70%) de individuos de S. calliope y una menor (30%) de S. rufus entraron en torpor, pero estas frecuencias se mantuvieron contantes en el tiempo. En contraste, la fracci & oacute;n de individuos de S. platycercus que entraron en torpor se incrementaron con la fecha de captura, mientras que aquella de A. alexandri disminuy & oacute;. Nuestros resultados revelaron similitudes, pero tambi & eacute;n diferencias inesperadas en los colibr & iacute;es abeja migratorios Algunas estas diferencias son el resultado de desemejanzas en estrategias migratoria, Otras a & uacute;n no tienen explicaci & oacute;n, pero representan una oportunidad para mejor entender las causas y consecuencias de la migraci & oacute;n mediada por el torpor.

Abstract The large grackles in the subgenus Cassidix—Quiscalus mexicanus (Great-tailed Grackle), Q. major (Boat-tailed Grackle), and Q. palustris (Slender-billed Grackle)—form a clade with a complex evolutionary history of recent divergence and secondary contact. Quiscalus mexicanus is widespread from the western U.S. to Peru and encompasses 2 divergent mitochondrial lineages. Quiscalus major is found on the Atlantic and Gulf Coasts of the U.S. and shows striking geographic variation in eye color. Quiscalus palustris was endemic to central Mexico but went extinct during the early 20th century. Previous research has called into question the monophyly of Q. mexicanus and has suggested that Q. major and Q. mexicanus may hybridize in Texas and Louisiana. Additionally, the patterns of genetic structuring among subspecies within Q. mexicanus and Q. major are unclear. We resolved many of these questions by sequencing and analyzing data from nuclear ultraconserved elements (UCEs) and mitochondrial DNA collected from samples representing all 13 subspecies in the Cassidix clade. Our results show no evidence of admixture between Q. major and Q. mexicanus, suggesting that if hybrids occur in the contact zone, they are infertile or rare. Our results also support the monophyly of Q. major and Q. mexicanus, with Q. palustris likely sister to a unified Q. mexicanus, contrary to evidence from mitochondrial DNA. Finally, these data resolve intraspecific relationships in the Cassidix complex, several of which differ from current subspecies-level taxonomy, and show that geographic breaks, not eye color differences, structure genetic variation within Q. major.

The complex geological and geographic history of the Philippine Archipelago has shaped its terrestrial biodiversity and patterns of endemism. Some explanations for the structuring of Philippine diversity, such as the oceanic origin of the islands or Pleistocene Aggregate Island Complexes (PAICs), are well-supported and accepted predictors for patterns of biodiversity. Other factors, such as the recently documented Mid-Sierra Filter Zone, remain underexplored and in need of additional research. In the present study, we employ restriction site-associated DNA sequencing (RADseq) to reconstruct the evolutionary history of the Philippine-endemic bird genus Sterrhoptilus. We corroborate the paraphyletic relationship of the two black-crowned species (Sterrhoptilus nigrocapitatus and S. affinis) recently recovered by Hosner et al. and find that Sterrhoptilus broadly follows phylogenetic patterns predicted by PAICs. We also learn more about within-PAIC diversity and uncover numerous hybrid individuals in central Luzon, a well-known population turnover boundary for many taxa. The pattern of backcrossed individuals and unsampled geographic areas gives an incomplete picture of the hybrid zone but supports the possibility of a broad region of overlap and hybridization between two species in the Mid-Sierra Madre. We used genomic data to investigate the species- and population-level relationships in the bird genus Sterrhoptilus, which support the current 4-species delimitation recovered in an earlier study using mitochondrial DNA. We investigated a poorly known hybrid zone between S. dennistouni and S. affinis in the Mid-Sierra Madre, a common region for species turnover on Luzon. All individuals sampled from the putative hybrid zone showed some amount of hybrid ancestry, but no first- or second-generation hybrids were sampled. We suggest that the lack of early generation hybrids could be caused by a large or moving hybrid zone, historical hybridization, or reduced fitness of hybrids.

Previous studies have shown that duration of the post-breeding molt in temperate-zone passerines is inversely related to migration distance. However, it is unclear whether this relationship arises directly-because long-distance migration selects for more rapid molt, or indirectly-because long-distance migration precludes double brooding and allows molt to begin earlier under more favorable environmental conditions. We investigated this issue by examining the effects of migration distance, frequency of double brooding, and wing length on the timing and duration of the post-breeding molt for 33 passerine species captured during banding operations at Powdermill Avian Research Center in southwestern Pennsylvania, USA. Consistent with predictions of the indirect pathway hypothesis, we found that long-distance migration is strongly associated with single brooding, and single-brooded species initiate flight-feather molt about one month earlier than double-brooded species. However, contrary to the predictions of the indirect pathway hypothesis, frequency of double brooding has no effect on molt duration; instead, molt duration increases with increasing wing length and decreases with increasing migration distance. The strong negative relationship between migration distance and molt duration is consistent with the direct pathway hypothesis and suggests that the time constraints imposed by long-distance migration lead directly to natural selection for rapid post-breeding molt. Our results also indicate that the rapid molt of long-distance migrants is achieved by an increase in the number of remiges being replaced simultaneously (molt intensity), and apparently also by an increase in the rate at which remiges grow. Unexpectedly, our estimates of molt duration were bimodally distributed, with 25 species showing rapid molt (40-65 days) and 8 showing slow molt (82-103 days). Overall, our findings clarify the effects of migration distance, double brooding, and wing length on phenology of passerine post-breeding molt, and highlight opportunities to expand avian life-history theory to incorporate interspecific variation in molt strategies. Adults of most songbird species in the northern temperate zone completely replace the feathers in their plumage during an annual post-breeding molt. Because it is energetically and nutritionally demanding, molt is usually scheduled to avoid overlap with two other demanding phases of the songbird annual cycle, breeding and migration. We investigated how migration distance, the frequency of double brooding, and wing length influence the timing and duration of post-breeding molt in 33 songbird species captured during banding operations at Powdermill Avian Research Center in southwest Pennsylvania, USA. Our results indicate that long-distance migrants are usually single-brooded, and single-brooded species initiate molt about one month earlier than double-brooded species that typically continue nesting through late summer. Although larger birds have longer molt durations, molt duration nonetheless decreases with increasing migration distance, suggesting that the time constraints imposed by long-distance migration lead directly to natural selection for rapid post-breeding molt. Estudios previos han demostrado que la duraci & oacute;n de la muda post-reproductiva en paseriformes de zonas templadas est & aacute; inversamente relacionada con la distancia de migraci & oacute;n. Sin embargo, no est & aacute; claro si esta relaci & oacute;n surge de manera directa-porque la migraci & oacute;n de larga distancia selecciona mudas m & aacute;s r & aacute;pidas-o indirectamente-porque la migraci & oacute;n de larga distancia impide la doble nidada y permite que la muda comience antes bajo condiciones ambientales m & aacute;s favorables. Investigamos esta cuesti & oacute;n examinando los efectos de la distancia de migraci & oacute;n, la frecuencia de doble nidada y la longitud del ala sobre el momento y la duraci & oacute;n de la muda post-reproductiva en 33 especies de paseriformes capturadas durante campa & ntilde;as de anillado en el Centro de Investigaci & oacute;n de Aves Powdermill, en el suroeste de Pensilvania, EUA. En concordancia con las predicciones de la hip & oacute;tesis de la v & iacute;a indirecta, encontramos que la migraci & oacute;n de larga distancia est & aacute; fuertemente asociada con una sola nidada, y que las especies con una sola nidada inician la muda de las plumas del vuelo aproximadamente un mes antes que las especies con doble nidada. Sin embargo, en contraste con las predicciones de la hip & oacute;tesis de la v & iacute;a indirecta, la frecuencia de doble nidada no tiene efecto sobre la duraci & oacute;n de la muda; en cambio, la duraci & oacute;n de la muda aumenta con la longitud del ala y disminuye con la distancia de migraci & oacute;n. La fuerte relaci & oacute;n negativa entre la distancia de migraci & oacute;n y la duraci & oacute;n de la muda es consistente con la hip & oacute;tesis de la v & iacute;a directa y sugiere que las restricciones temporales impuestas por la migraci & oacute;n de larga distancia conducen directamente a la selecci & oacute;n natural de una muda post-reproductiva r & aacute;pida. Nuestros resultados tambi & eacute;n indican que la muda r & aacute;pida de los migrantes de larga distancia se logra mediante un aumento en el n & uacute;mero de r & eacute;miges que se reemplazan simult & aacute;neamente (intensidad de la muda), y aparentemente tambi & eacute;n mediante un aumento en la tasa de crecimiento de estas plumas. De manera inesperada, nuestras estimaciones de la duraci & oacute;n de la muda presentaron una distribuci & oacute;n bimodal, con 25 especies que mostraron una muda r & aacute;pida (40-65 d & iacute;as) y 8 que mostraron una muda lenta (82-103 d & iacute;as). En conjunto, nuestros resultados aclaran los efectos de la distancia de migraci & oacute;n, la doble nidada y la longitud del ala sobre la fenolog & iacute;a de la muda post-reproductiva en paseriformes, y destacan oportunidades para ampliar la teor & iacute;a de historia de vida de las aves incorporando la variaci & oacute;n interespec & iacute;fica en las estrategias de muda.

Life-history theory predicts a trade-off between current and future reproductive effort and, in this context, the terminal investment hypothesis proposes that reproductive investment, and consequently breeding success, should increase at older ages. We analyzed how relative minimum age related to breeding investment and success in Tachycineta leucopyga (Chilean Swallow) females across 6 breeding seasons in northwestern Argentine Patagonia. We also examined age associations between laying date and physical condition. Our results showed no evidence that reproductive investment increased with age. However, older females laid earlier and achieved higher breeding success than younger ones, which may be related to age-associated differences such as experience or skill. We propose that older females may refine foraging efficiency, increasing the quality or quantity of food delivered per visit, while maintaining self-care; physical condition slightly improved from 1- to 2-year-old females but remained similar in older females. Given that migratory aerial insectivores are particularly vulnerable to global climate change, understanding how reproductive investment and success vary with age provides essential life-history data to identify critical demographic constraints. Such information is particularly scarce in South America, where information on breeding costs and survival remains limited and hinders the development of effective conservation strategies. Reproduction is demanding for birds, especially females, so they must balance the effort between raising young now and maintaining their own survival to reproduce again in the future. We studied how reproductive effort and breeding success changed with age in female Tachycineta leucopyga (Chilean Swallow), a migratory bird that feeds on flying insects. Older females laid their eggs earlier and had greater breeding success, even though they did not lay more eggs or feed their chicks more often. We suggest that older swallows gain experience, for example, by migrating at the right time and becoming more efficient at finding food, which helps them feed their chicks with better or more food on each visit during the nestling period, leading to higher breeding success. These findings help us understand how birds adapt to changing environments and why protecting older, experienced birds may have important consequences for population persistence. La teor & iacute;a de historia de vida predice un compromiso entre el esfuerzo reproductivo presente y futuro. Dentro de este marco te & oacute;rico, la hip & oacute;tesis de inversi & oacute;n terminal propone que la inversi & oacute;n reproductiva y, en consecuencia, el & eacute;xito reproductivo, deber & iacute;a aumentar en clases de edad mayores. En este estudio, analizamos la relaci & oacute;n entre la edad m & iacute;nima relativa y la inversi & oacute;n y el & eacute;xito reproductivo de las hembras de Tachycineta leucopyga a lo largo de seis temporadas reproductivas en el noroeste de la Patagonia Argentina. Tambi & eacute;n analizamos la posible asociaci & oacute;n entre la edad y la fecha de puesta o la condici & oacute;n f & iacute;sica. Nuestros resultados no mostraron evidencia de que la inversi & oacute;n reproductiva aumente con la edad. Sin embargo, las hembras mayores pusieron huevos m & aacute;s temprano y lograron un mayor & eacute;xito reproductivo que las m & aacute;s j & oacute;venes, lo cual podr & iacute;a estar relacionado con diferencias dadas por la edad en experiencia o habilidades. Proponemos que las hembras mayores podr & iacute;an mejorar la eficiencia en la b & uacute;squeda y obtenci & oacute;n de alimentos, aumentando la calidad o la cantidad de alimento entregado en cada visita al nido, al mismo tiempo que mantienen su propia condici & oacute;n f & iacute;sica; de hecho, la condici & oacute;n f & iacute;sica fue levemente mejor en las hembras de dos a & ntilde;os con respecto a las de un a & ntilde;o, aunque se mantuvo similar en las hembras m & aacute;s viejas. Dado que las aves insect & iacute;voras migratorias son particularmente vulnerables al cambio clim & aacute;tico global, entender c & oacute;mo var & iacute;an la inversi & oacute;n y el & eacute;xito reproductivo con la edad proporciona datos esenciales de historia de vida para identificar limitaciones demogr & aacute;ficas cr & iacute;ticas. Esta informaci & oacute;n es particularmente escasa en Sudam & eacute;rica, donde los datos sobre los costos reproductivos y la supervivencia siguen siendo limitados, dificultando el desarrollo de estrategias efectivas de conservaci & oacute;n.

Polygamous birds with lek-mating breeding systems often show site fidelity to display sites, leading to spatio-temporal stability of traditional leks that can persist for decades. Here, we used a mark-recapture framework to study between-year lek fidelity among adult male and female Gallinago media (Great Snipe), for two distinct breeding populations in Eastern Europe and Scandinavia. We evaluated the effects of individual body size, lek size, and distance among leks on the probability of changing lek between seasons. Moreover, we were able to obtain more precise estimates of annual survival for G. media beyond previously obtained population parameters from a single lek and for males only. G. media had a low but stable annual apparent survival across both sexes and breeding populations (S = 0.571 +/- 0.019 SE). Birds showed high between-year fidelity to their leks, as we detected a relatively low probability of changing leks between seasons (Psi = 0.18 +/- 0.019 SE). Despite pronounced differences in breeding behavior between sexes, as well as habitat differences between breeding populations, they did not influence lek fidelity, and neither did individual body size nor distance between leks. However, birds at larger leks were less likely to move elsewhere in the following years. Understanding the drivers of lek changing behavior provides insights into the evolution of a lek mating strategy, and accounting for site fidelity is crucial for studying population dynamics and space use patterns. Taking the inherent limitations of estimates based on mark-capture models into account, our estimates of annual survival and site fidelity for G. media can be used to inform management decisions and conservation strategies. Return rates to the same breeding site in different seasons vary among mating systems in waders. Monogamous birds tend to be more site faithful than polygamous ones, but in lekking species, both sexes are often highly faithful to the leks. We studied Gallinago media (Great Snipe) in two distinct breeding populations to measure both annual survival and lek fidelity, using long-term ringing data. We found that G. media rarely switch leks between breeding seasons, and high lek fidelity is shared by both sexes and both breeding populations of this species. Site fidelity likely explains how traditional leks can be in the same place for decades, frequently exceeding the lifespan of a single individual. Given the low annual survival estimates of adults, the information on lek locations must be easily accessible for the first-time breeders, additionally facilitating stability of traditional lekking sites. Las aves pol & iacute;gamas con sistemas reproductivos basados en leks suelen mostrar fidelidad al sitio de exhibici & oacute;n, lo que conduce a la estabilidad espacio-temporal de leks tradicionales que pueden persistir durante d & eacute;cadas. Aqu & iacute; utilizamos un enfoque de marcado-recaptura para estudiar la fidelidad interanual a los leks en machos y hembras adultos de Gallinago media en dos poblaciones reproductivas distintas de Europa oriental y Escandinavia. Evaluamos los efectos del tama & ntilde;o corporal individual, el tama & ntilde;o del lek y la distancia entre leks sobre la probabilidad de cambiar de lek entre temporadas. Adem & aacute;s, pudimos obtener estimaciones m & aacute;s precisas de la supervivencia anual de G. media m & aacute;s all & aacute; de los par & aacute;metros poblacionales previamente obtenidos a partir de un & uacute;nico lek y solo para machos. Gallinago media present & oacute; una supervivencia aparente anual baja pero estable en ambos sexos y poblaciones reproductivas (S = 0.571 +/- 0.019 EE). Las aves mostraron una alta fidelidad interanual a sus leks, ya que detectamos una probabilidad relativamente baja de cambiar de lek entre temporadas (Psi = 0.18 +/- 0.019 EE). A pesar de las marcadas diferencias en el comportamiento reproductivo entre sexos, as & iacute; como de las diferencias de h & aacute;bitat entre las poblaciones reproductivas, estos factores no influyeron en la fidelidad al lek, ni tampoco lo hicieron el tama & ntilde;o corporal individual o la distancia entre leks. Sin embargo, las aves en leks m & aacute;s grandes tuvieron menor probabilidad de desplazarse a otros sitios en los a & ntilde;os siguientes. Comprender los factores que determinan el cambio de lek proporciona informaci & oacute;n sobre la evoluci & oacute;n de la estrategia reproductiva basada en leks, y considerar la fidelidad al sitio es crucial para estudiar la din & aacute;mica poblacional y los patrones de uso del espacio. Teniendo en cuenta las limitaciones inherentes de las estimaciones basadas en modelos de marcado-recaptura, nuestras estimaciones de supervivencia anual y fidelidad al sitio para G. media pueden utilizarse para orientar decisiones de manejo y estrategias de conservaci & oacute;n.

Parental investment can shape offspring growth, with consequences for sibling-sibling competition and survival. Altricial birds often face severe mortality bottlenecks before they reach independence; their eggs can vary in attributes including size, amounts of internal components (yolk, albumen), and concentrations of micronutrients (e.g., carotenoids, vitamins) and hormones. Egg composition may vary with maternal resource availability and egg-laying order. If eggs within the clutch hatch asynchronously, variation in contents with laying order could exacerbate nestling size hierarchies to promote adaptive brood reduction or could mitigate the cost of maladaptive asynchrony by enhancing embryonic growth in later-laid eggs. We reviewed the avian egg-laying order literature to identify existing knowledge gaps and quantified the mass of multiple egg components, eggshell coloration, and concentrations of 12 yolk steroids and 8 yolk vitamins and carotenoids in freshly laid eggs (n = 100) of wild Turdus migratorius (American Robins) collected in Illinois, USA, in the early and late halves of their breeding season. Laying order significantly influenced eggshell color, egg and yolk mass, and the concentrations of 4 yolk steroids and 7 yolk vitamins and carotenoids. First-laid eggs, regardless of seasonal timing of lay, were lightest and had the highest concentrations of yolk androgens and progestogens. Yolk carotenoid concentrations decreased with laying order in the early breeding season, and eggshell coloration covaried with carotenoid concentrations. To test for laying order effects on embryonic development, we also incubated eggs of known laying order (n = 64) and assessed embryonic metabolic development, shifts in yolk hormone and carotenoid concentrations, and size similar to 4 days before hatch. In lab-incubated eggs, embryonic heart rate, shifts in yolk carotenoid and hormone concentrations, and pre-hatch size were not related to laying order. If first-laid eggs receive reduced maternal investment to promote brood survival in this population, the effects of this investment strategy are not realized in embryonic traits. Parents are constrained by time and resources, and parental investment in offspring can vary, even among siblings in the same family. Birds may lay multiple eggs in a single family, but may not allocate each egg the same resources, perhaps to influence sibling competition once the eggs hatch. While past research has assessed some egg components and their relationship to the order eggs were laid in a single family, little is known about how each component relates to each other and to parental strategies. We studied the resources invested in Turdus migratorius (American Robin) eggs, asking which resources varied among eggs and time of year. The first egg robins laid in each clutch were smaller than the rest but had higher concentrations of carotenoids, vitamins, and steroid hormones. When artificially incubated in a laboratory, the eggs of different laying orders did not produce embryos of different sizes despite differences in egg resources. La inversi & oacute;n parental puede moldear el crecimiento de la descendencia, con consecuencias para la competencia entre hermanos y la supervivencia. Las aves altriciales a menudo enfrentan cuellos de botella severos de mortalidad antes de alcanzar la independencia; sus huevos pueden variar en atributos que incluyen tama & ntilde;o, cantidades de componentes internos (yema, alb & uacute;mina), y concentraciones de micronutrientes (e.g., carotenoides, vitaminas) y hormonas. La composici & oacute;n del huevo puede variar seg & uacute;n la disponibilidad de recursos maternos y el orden de puesta. Si los huevos dentro de la puesta eclosionan de manera asincr & oacute;nica, la variaci & oacute;n en el contenido seg & uacute;n el orden de puesta podr & iacute;a exacerbar las jerarqu & iacute;as de tama & ntilde;o entre polluelos para promover una reducci & oacute;n adaptativa de la nidada, o bien mitigar el costo de una asincron & iacute;a no adaptativa al mejorar el crecimiento embrionario en los huevos puestos m & aacute;s tarde. Revisamos la literatura sobre el orden de puesta en aves para identificar vac & iacute;os de conocimiento existentes y cuantificamos la masa de m & uacute;ltiples componentes del huevo, la coloraci & oacute;n de la c & aacute;scara, y las concentraciones de 12 esteroides de la yema y 8 vitaminas y carotenoides de la yema en huevos recolectados reci & eacute;n puestos (n = 100) por individuos silvestres de Turdus migratorius en Illinois, EUA, durante la primera y la segunda mitad de la temporada reproductiva. El orden de puesta influy & oacute; significativamente en el color de la c & aacute;scara, la masa del huevo y de la yema, y en las concentraciones de 4 esteroides de la yema y 7 vitaminas y carotenoides de la yema. Los primeros huevos puestos, independientemente del momento de la temporada en que se produjo la puesta, fueron los m & aacute;s livianos y presentaron las mayores concentraciones de andr & oacute;genos y progest & aacute;genos en la yema. Las concentraciones de carotenoides en la yema disminuyeron con el orden de puesta en la primera parte de la temporada reproductiva, y la coloraci & oacute;n de la c & aacute;scara covari & oacute; con las concentraciones de carotenoides. Para evaluar los efectos del orden de puesta sobre el desarrollo embrionario, tambi & eacute;n incubamos huevos con orden de puesta conocido (n = 64) y evaluamos el desarrollo metab & oacute;lico embrionario, los cambios en las concentraciones de hormonas y carotenoides de la yema, y el tama & ntilde;o aproximadamente 4 d & iacute;as antes de la eclosi & oacute;n. En los huevos incubados en laboratorio, la frecuencia card & iacute;aca embrionaria, los cambios en las concentraciones de carotenoides y hormonas de la yema, y el tama & ntilde;o previo a la eclosi & oacute;n no estuvieron relacionados con el orden de puesta. Si los primeros huevos puestos reciben una inversi & oacute;n materna reducida para promover la supervivencia de la nidada en esta poblaci & oacute;n, los efectos de esta estrategia de inversi & oacute;n no se manifiestan en rasgos embrionarios.

Understanding the ecological and demographic factors influencing reproductive success is essential for effective conservation planning. This is particularly critical for species like Ardea insignis (White-bellied Heron), which is critically endangered and survives in fragmented populations. We monitored 3-4 active breeding pairs in Bhutan from 2016 to 2025, focusing on the first egg-laying date and reproductive outcomes. Although all nests were spatially dispersed (7-70 km apart), pairs showed high site fidelity for multiple years. Nests were primarily built on broad-leaved trees near major river channels, at elevations of 280-540 m, often located in proximity to the confluence of the main river and a major tributary. The nests were in secluded areas with minimal disturbance, although not exclusively away from human settlement. Most nests were located on the opposite bank from human settlements, in narrow valleys where fast-flowing rivers serve as physical barriers to human approach. We observed variation in the first egg-laying dates from year to year, with this variability increasing in recent years. We also observed that some pairs consistently initiated early breeding and achieved higher success rates, while others experienced unpredictable outcomes. Overall, clutch sizes varied from 2 to 4 eggs with a mean of 3.10 +/- 0.52 SD, hatchlings ranged from 0 to 4 with a mean of 1.55 +/- 1.23 SD, and fledglings also ranged from 0 to 4 per nest with a mean of 1.12 +/- 1.24 SD. We recorded renesting attempts following early clutch failures; however, all these attempts were unsuccessful. An extremely small population with increasing variability and unpredictable breeding output suggests that the population is at risk of extinction. We recommend management actions that prioritize the protection of all breeding pairs and critical habitats, as well as further research on breeding phenology and reproductive performance. Ardea insignis (White-bellied Heron) is one of the rarest and most critically endangered herons, and a species of significant global conservation concern. Fewer than 60 mature individuals are estimated to exist in the wilds of Bhutan, Northeast India, Myanmar, and China, with a few active breeding pairs recorded only in Bhutan and Northeast India. We observed variability in breeding timing, with first egg laying dates ranging from as early as February 9 to as late as June 13 within a similar breeding habitat. Successful pairs tend to maintain long-term bonds, exhibit high site fidelity, and consistently initiate early breeding, achieving higher success rates, while others experience unpredictable outcomes. We observed that at least 50% of the pairs that failed in the first attempt re-clutched, especially if the nest failed at an early stage. However, none of the replacement clutches (from renesting attempts) succeeded in fledging any chicks between 2016 and 2025. Nest failures were mainly caused by egg predation by monkeys and mesocarnivores, disturbances, late nesting, sexual conflicts, infanticide, chicks falling from the nest, adult mortality, and hazardous weather. Comprender los factores ecol & oacute;gicos y demogr & aacute;ficos que influyen en el & eacute;xito reproductivo es esencial para una planificaci & oacute;n eficaz de la conservaci & oacute;n. Esto es particularmente cr & iacute;tico para especies como Ardea insignis, que se encuentra en peligro cr & iacute;tico y sobrevive en poblaciones fragmentadas. Monitoreamos 3-4 parejas reproductivas activas en But & aacute;n entre 2016 y 2025, enfoc & aacute;ndonos en la fecha de puesta del primer huevo y en los resultados reproductivos. Aunque todos los nidos estaban espacialmente dispersos (separados entre 7 y 70 km), las parejas mostraron alta fidelidad al sitio durante varios a & ntilde;os. Los nidos se construyeron principalmente en & aacute;rboles de hoja ancha cerca de los principales canales fluviales, a elevaciones de 280-540 m, a menudo ubicados cerca de la confluencia del r & iacute;o principal con un tributario importante. Los nidos se encontraron en & aacute;reas aisladas con m & iacute;nima perturbaci & oacute;n, aunque no necesariamente alejadas de asentamientos humanos. La mayor & iacute;a de los nidos se ubicaron en la ribera opuesta a los asentamientos humanos, en valles estrechos donde r & iacute;os de corriente r & aacute;pida act & uacute;an como barreras f & iacute;sicas que dificultan el acceso humano. Observamos variaci & oacute;n entre a & ntilde;os en las fechas de puesta del primer huevo, con un aumento de esta variabilidad en los & uacute;ltimos a & ntilde;os. Tambi & eacute;n observamos que algunas parejas iniciaron consistentemente la reproducci & oacute;n de forma temprana y lograron mayores tasas de & eacute;xito, mientras que otras experimentaron resultados impredecibles. En general, el tama & ntilde;o de puesta vari & oacute; entre 2 y 4 huevos con una media de 3.10 +/- 0.52 DE, el n & uacute;mero de polluelos eclosionados vari & oacute; entre 0 y 4 con una media de 1.55 +/- 1.23 DE, y el n & uacute;mero de volantones tambi & eacute;n vari & oacute; entre 0 y 4 por nido con una media de 1.12 +/- 1.24 DE. Registramos intentos de re-nidificaci & oacute;n luego de fracasos tempranos de la puesta; sin embargo, todos estos intentos fracasaron. Una poblaci & oacute;n extremadamente peque & ntilde;a con variabilidad creciente y resultados reproductivos impredecibles sugieren que la poblaci & oacute;n est & aacute; en riesgo de extinci & oacute;n. Recomendamos acciones de manejo que prioricen la protecci & oacute;n de todas las parejas reproductivas y de los h & aacute;bitats cr & iacute;ticos, as & iacute; como investigaciones adicionales sobre la fenolog & iacute;a reproductiva y el desempe & ntilde;o reproductivo.

Animal diets are shaped both by the availability of resources and preferences for certain food items over others. Environmental conditions can affect the availability of arthropod prey, and animals that rely on arthropods for food may need to shift their diet across years with different climatic conditions. Here, we tested for differences in Poecile gambeli (Mountain Chickadee) nestling diet between two elevational sites and across two years with extreme climatic differences. We present the first study characterizing P. gambeli nestling diet using fecal DNA metabarcoding. Fecal samples were obtained from nestlings at high- and low-elevation sites in the northern Sierra Nevada mountains, USA in 2022 and 2023. We also sampled arthropods on conifer trees during the fecal sampling period. The first year was characterized by low-to-average snow accumulation, while the second year was a heavy snow year. We used these naturally occurring climatic extremes to test for differences in diet and food availability between years and elevations. There were significant differences in the family-level community composition of available arthropods between elevations and years, except at low elevation, where community composition was not significantly different between years. There were also significant differences in the community composition of nestling diet between elevations and years. Differences in diet were associated with differences in food availability for commonly sampled arthropod families, but chickadees exhibited both selection for and avoidance of some prey families. Overall, chickadees utilized prey resources from a diverse suite of taxa and showed flexibility in provisioned diet both across small spatial scales and between years, potentially making them highly resilient to climate-related changes in prey availability. We studied Poecile gambeli (Mountain Chickadee) nestling diet and prey preference at 2 elevational sites in the Sierra Nevada mountains across 2 years with extreme differences in overwinter snow accumulation.Fecal DNA metabarcoding was used to document arthropod prey in nestling diets, and beat sheet sampling was used to measure the availability of arthropod prey in the environment.Family-level composition of arthropod communities in the environment differed between years and elevations, except at the lower elevation site, where the comparison between years was not significant.Nestling diet composition was significantly different between years and elevations, reflecting differences in the availability of certain prey taxa.Chickadees showed preferences for certain arthropod prey and avoided others, but overall, parents were more likely to feed their young items that were more available based on arthropod sampling. Las dietas animales est & aacute;n determinadas tanto por la disponibilidad de recursos como por la preferencia por ciertos & iacute;tems alimenticios sobre otros. Las condiciones ambientales pueden afectar la disponibilidad de presas artr & oacute;podas, y los animales que dependen de artr & oacute;podos como alimento pueden necesitar modificar su dieta entre a & ntilde;os con diferentes condiciones clim & aacute;ticas. Aqu & iacute; evaluamos diferencias en la dieta de polluelos de Poecile gambeli entre dos sitios a distinta elevaci & oacute;n y entre a & ntilde;os con diferencias clim & aacute;ticas extremas. Presentamos el primer estudio que caracteriza la dieta de polluelos de P. gambeli mediante metabarcoding de ADN fecal. Se obtuvieron muestras fecales de polluelos durante dos a & ntilde;os en sitios de alta y baja elevaci & oacute;n en el norte de las monta & ntilde;as de Sierra Nevada, EUA. Tambi & eacute;n muestreamos artr & oacute;podos en & aacute;rboles de con & iacute;feras durante el per & iacute;odo de muestreo fecal. El primer a & ntilde;o se caracteriz & oacute; por una acumulaci & oacute;n de nieve entre baja a promedio, mientras que el segundo fue un a & ntilde;o de intensa acumulaci & oacute;n de nieve. Utilizamos estos extremos clim & aacute;ticos naturales para evaluar diferencias en la dieta y en la disponibilidad de alimento entre a & ntilde;os y elevaciones. Hubo diferencias significativas en la composici & oacute;n comunitaria a nivel de familia de los artr & oacute;podos disponibles entre elevaciones y a & ntilde;os, excepto en la elevaci & oacute;n baja, donde la composici & oacute;n comunitaria no difiri & oacute; significativamente entre a & ntilde;os. Tambi & eacute;n hubo diferencias significativas en la composici & oacute;n comunitaria de la dieta de los polluelos entre elevaciones y a & ntilde;os. Las diferencias en la dieta se asociaron con diferencias en la disponibilidad de alimento para las familias de artr & oacute;podos com & uacute;nmente muestreadas, pero los carboneros mostraron tanto selecci & oacute;n como evitaci & oacute;n de algunas familias de presas. En conjunto, los carboneros utilizaron recursos presa provenientes de un conjunto diverso de taxones y mostraron flexibilidad en la dieta suministrada tanto a peque & ntilde;as escalas espaciales como entre a & ntilde;os, lo que potencialmente los hace altamente resilientes a cambios en la disponibilidad de presas asociados al clima.

Unequal representation of focal research areas can arise during the initial stages of project development when investigators make decisions about what, when, and where to study. Regarding when research is conducted, publications on vertebrates are strongly skewed toward breeding-stage studies, leaving sizeable gaps in our knowledge pertaining to behavior and demography in nonbreeding stages. Here, we quantified how the focus on different annual cycle stages has changed over the past 64 years in the field of ornithology, and tested 3 hypotheses to explain underlying correlates of the focus on different stages. We surveyed field-based studies published in Ornithology from 1960 to 2024 and documented the annual cycle stages examined, regions of study, migratory strategies of focal species, and author affiliation for each paper. The tendency to conduct breeding-stage research in ornithology became more, rather than less, pronounced over the 64-year interval, and breeding-stage research was more common when field work focused on migratory species. Therefore, investigators, authors, and editors could likely increase representation of other annual-cycle stages by supporting, conducting, and publishing more studies in the tropics and more studies using remote tracking technologies. More nonbreeding and year-round studies are necessary to fully understand the ecology and evolution of species and develop the most effective strategies for conservation. Our collective scientific knowledge is based largely on published research, but unequal representation in the context and focus of studies can lead to gaps in understanding. We summarized the timing, location, authorship, and focus of field research on birds published in Ornithology between 1960 and 2024. Research published in Ornithology was heavily focused on the breeding stage, and this skew increased over time. The overrepresentation of breeding-stage topics in research was linked to constraints imposed by species traits. Our results highlight gaps in avian research, which future investigators can fill by focusing on less-studied, but important, stages in the annual cycle of birds. La representaci & oacute;n desigual de las & aacute;reas de investigaci & oacute;n focales puede surgir durante las etapas iniciales del desarrollo de los proyectos, cuando los investigadores toman decisiones sobre qu & eacute; estudiar, cu & aacute;ndo hacerlo y d & oacute;nde. En cuanto al momento en que se realiza la investigaci & oacute;n, las publicaciones sobre vertebrados est & aacute;n fuertemente sesgadas hacia estudios de la etapa reproductiva, lo que deja vac & iacute;os importantes en nuestro conocimiento sobre el comportamiento y la demograf & iacute;a durante las etapas no reproductivas. Aqu & iacute; cuantificamos c & oacute;mo ha cambiado el enfoque sobre las distintas etapas del ciclo anual a lo largo de los & uacute;ltimos 64 a & ntilde;os en el campo de la ornitolog & iacute;a, y pusimos a prueba tres hip & oacute;tesis para explicar los factores subyacentes asociados al & eacute;nfasis en distintas etapas. Relevamos estudios de campo publicados en Ornithology entre 1960 y 2024, y documentamos para cada art & iacute;culo las etapas del ciclo anual analizadas, las regiones de estudio, las estrategias migratorias de las especies focales y la afiliaci & oacute;n de los autores. La tendencia a realizar investigaciones centradas en la etapa reproductiva en ornitolog & iacute;a se volvi & oacute; m & aacute;s pronunciada, y no menos, a lo largo del per & iacute;odo de 64 a & ntilde;os, y este tipo de estudios fue m & aacute;s frecuente cuando el trabajo de campo se enfoc & oacute; en especies migratorias. Por lo tanto, investigadores, autores y editores podr & iacute;an aumentar la representaci & oacute;n de otras etapas del ciclo anual apoyando, realizando y publicando m & aacute;s estudios en los tr & oacute;picos y m & aacute;s trabajos que utilicen tecnolog & iacute;as de seguimiento remoto. Se necesitan m & aacute;s estudios sobre etapas no reproductivas y estudios a lo largo de todo el a & ntilde;o para comprender plenamente la ecolog & iacute;a y evoluci & oacute;n de las especies y para desarrollar estrategias de conservaci & oacute;n m & aacute;s efectivas.

Pigeons and doves began to diversify shortly after the Cretaceous-Paleogene (K-Pg) boundary, subsequently colonizing new land masses via long-distance dispersal. Extant pigeon and dove species occupy a range of habitats and exhibit both migratory and homing behaviors. Here, we used whole-genome sequencing to infer the phylogenetic relationships of 108 pigeon and dove species; a significant expansion of taxa compared to prior phylogenomic studies. Phylogenetic analysis using different methods produced trees that were largely consistent, except with regard to the placement of the genus Macropygia, and generally follows subfamily and genus classification, with two exceptions. Given the similarities between trees, one of the resulting trees was used to examine molecular evolution in a candidate magnetoreceptor in birds, cryptochrome 4. A radical-pair within the cryptochrome 4 protein may allow birds to detect the Earth's magnetic field. Phylogenetic studies have the potential to identify evolutionary changes within the cryptochrome 4 gene and protein sequences that are associated with behavioral changes, and may inform subsequent functional studies. By examining cryptochrome 4 guided by a phylogenomic reconstruction of pigeon and dove species, we find that three amino acid changes in cryptochrome 4 are under positive selection in some species. The three changes occur within two different functional regions within cryptochrome 4, but are not statistically significantly associated with changes in dispersal and foraging behaviors. Long-distance dispersal has shaped the diversification of pigeons and doves, a diverse group of birds, which includes a species capable of homing. To understand the evolutionary relationships of pigeons and doves, 5,464 genes were used to infer an evolutionary tree that includes 108 different species, a significant expansion compared to earlier studies. A phylogenetic tree of pigeons and doves was used to examine the evolution of the cryptochrome 4 gene, which encodes a protein that may allow birds to detect magnetic fields during navigation. The results highlight specific amino acid changes in cryptochrome 4 that may alter magnetic orientation, potentially informing future studies. Las palomas y t & oacute;rtolas comenzaron a diversificarse poco despu & eacute;s del l & iacute;mite Cret & aacute;cico-Pale & oacute;geno (K-Pg), colonizando posteriormente nuevas masas terrestres mediante dispersi & oacute;n a larga distancia. Las especies actuales de palomas y t & oacute;rtolas ocupan una amplia variedad de h & aacute;bitats y exhiben tanto comportamientos migratorios como de retorno al sitio de origen. Aqu & iacute; utilizamos la secuenciaci & oacute;n completa del genoma para inferir las relaciones filogen & eacute;ticas de 108 especies de palomas y t & oacute;rtolas; una expansi & oacute;n significativa del n & uacute;mero de taxones en comparaci & oacute;n con estudios filogen & oacute;micos previos. El an & aacute;lisis filogen & eacute;tico mediante distintos m & eacute;todos produjo & aacute;rboles en gran medida consistentes entre s & iacute;, excepto en lo que respecta a la ubicaci & oacute;n del g & eacute;nero Macropygia, y en general sigue la clasificaci & oacute;n por subfamilia y g & eacute;nero, con 2 excepciones. Dadas las similitudes entre los & aacute;rboles, uno de los & aacute;rboles resultantes se utiliz & oacute; para examinar la evoluci & oacute;n molecular de un potencial magnetorreceptor en aves, el criptocromo 4. Un par radical dentro de la prote & iacute;na criptocromo 4 puede permitir que las aves detecten el campo magn & eacute;tico terrestre. Los estudios filogen & eacute;ticos tienen el potencial de identificar cambios evolutivos en el gen y en las secuencias proteicas de criptocromo 4 que est & eacute;n asociados con cambios conductuales y que puedan orientar estudios funcionales posteriores. Al examinar el criptocromo 4 guiados por una reconstrucci & oacute;n filogen & oacute;mica de especies de palomas y t & oacute;rtolas, encontramos que tres cambios de amino & aacute;cidos en el criptocromo 4 est & aacute;n bajo selecci & oacute;n positiva en algunas especies. Los tres cambios ocurren en dos regiones funcionales distintas dentro del criptocromo 4, pero no est & aacute;n estad & iacute;sticamente asociados de manera significativa con cambios en los comportamientos de dispersi & oacute;n y forrajeo.

Many socially monogamous bird species engage in multiple mating through extra-pair (EP) fertilizations, yet the role of female plumage in EP outcomes is under studied. Sexual selection involving EP fertilization is hypothesized to influence female trait evolution if heritable plumage variation informs EP mating decisions and EP mating decisions affect fitness. Here, we test for 2 key prerequisite patterns of sexual selection through EP fertilizations by asking: (1) is female reproductive success associated with EP fertilizations, and (2) are EP fertilizations associated with female plumage traits? Studying these 2 patterns is essential for better understanding how the costs and benefits of EP fertilizations should translate to sexual selection on female plumage. We provide a conceptual diagram to highlight how plumage traits of both members of a social pair can influence fertilizations within and outside their pair bond from the perspective of each sex. In our sample of 47 Hirundo rustica erythrogaster (North American Barn Swallow) social pairs, females who engaged in EP mating tended to fledge more offspring, and females with longer tails were more likely to mate with EP sires. Furthermore, female traits were more strongly associated with EP fertilizations than male traits for predicting both female and male EP outcomes. Finally, we found that female traits were not correlated with fecundity (total eggs laid) and found no association between fecundity and EP fertilizations. Thus, sexual selection on EP fertilizations may be more important than selection on fecundity for understanding female plumage variation in our study population. Taken together, we provide evidence for multiple conditions necessary for sexual selection on female plumage traits in H. r. erythrogaster that are likely also relevant for understanding female trait evolution in other socially monogamous birds. Understanding how traits evolve in female birds is essential for explaining the diversity of bird species. Fertilizations with birds other than a social mate in a shared nest ("extra-pair" fertilizations) are common in songbirds, yet we know little about how this process relates to the evolution of female plumage traits. We found that female Hirundo rustica (Barn Swallow) with longer tails were more likely to mate with multiple extra-pair males, and females with more extra-pair offspring also raised more total offspring over the course of a single breeding season. These findings mean that selection for extra-pair mating could help us understand how and why female plumage traits change over time. By giving female birds equal attention as male birds, we can gain a better understanding of how the phenotypic traits of birds change in populations and species overall. Muchas especies de aves socialmente mon & oacute;gamas participan en apareamientos m & uacute;ltiples mediante fertilizaciones extrapareja (EP); sin embargo, el papel del plumaje femenino en los resultados EP ha sido poco estudiado. Se plantea que la selecci & oacute;n sexual que involucra fertilizaciones EP puede influir en la evoluci & oacute;n de los rasgos femeninos si la variaci & oacute;n heredable del plumaje influye en las decisiones de apareamiento EP y si dichas decisiones afectan la aptitud biol & oacute;gica. Aqu & iacute; evaluamos dos patrones clave que constituyen prerrequisitos de la selecci & oacute;n sexual a trav & eacute;s de fertilizaciones EP preguntando: (1) & iquest;est & aacute; el & eacute;xito reproductivo femenino asociado con las fertilizaciones EP?, y (2) & iquest;est & aacute;n las fertilizaciones EP asociadas con rasgos del plumaje femenino? El estudio de estos dos patrones es esencial para comprender mejor c & oacute;mo los costos y beneficios de las fertilizaciones EP deber & iacute;an traducirse en selecci & oacute;n sexual sobre el plumaje femenino. Presentamos un diagrama conceptual para resaltar c & oacute;mo los rasgos del plumaje de ambos miembros de una pareja social pueden influir en las fertilizaciones dentro y fuera del v & iacute;nculo de pareja desde la perspectiva de cada sexo. En nuestra muestra de 47 parejas sociales de Hirundo rustica erythrogaster, las hembras que participaron en apareamientos EP tendieron a sacar adelante m & aacute;s cr & iacute;as, y las hembras con colas m & aacute;s largas tuvieron mayor probabilidad de aparearse con machos EP. Adem & aacute;s, los rasgos femeninos estuvieron m & aacute;s fuertemente asociados con las fertilizaciones EP que los rasgos masculinos para predecir tanto los resultados EP femeninos como masculinos. Finalmente, encontramos que los rasgos femeninos no estuvieron correlacionados con la fecundidad (total de huevos puestos) y no hallamos asociaci & oacute;n entre fecundidad y fertilizaciones EP. Por lo tanto, la selecci & oacute;n sexual sobre las fertilizaciones EP puede ser m & aacute;s importante que la selecci & oacute;n sobre la fecundidad para comprender la variaci & oacute;n del plumaje femenino en nuestra poblaci & oacute;n de estudio. En conjunto, aportamos evidencia de m & uacute;ltiples condiciones necesarias para la selecci & oacute;n sexual sobre los rasgos del plumaje femenino en H. r. erythrogaster, que probablemente tambi & eacute;n sean relevantes para comprender la evoluci & oacute;n de rasgos femeninos en otras aves socialmente mon & oacute;gamas.

Carotenoid-based coloration is a well-documented example of a condition-dependent trait, but much of the evidence supporting condition dependence of red carotenoid coloration comes from species that color their feathers primarily with 3-hydroxyechinenone, a red carotenoid produced from yellow dietary carotenoids via an unknown pathway. The condition dependence of red plumage in species that use the more common CYP2J19 and BDH1L enzymes to modify dietary yellow carotenoids into red ketocarotenoids is less well studied. We tested the hypothesis that captivity would negatively affect production of red pigments by male Cardinalis cardinalis (Northern Cardinal), a songbird with extensive red coloration produced via the CYP2J19/BDH1L pathway. We confined a group of wild-caught male cardinals in cages during molt, using captivity as a physiological challenge, and compared them to free-living cardinals. We provided captive birds with abundant zeaxanthin and lutein, the dietary yellow pigments that cardinals enzymatically convert into the red ketocarotenoids astaxanthin and alpha-doradexanthin, to ensure that insufficient carotenoid access would not limit production of red pigments. During molt, we measured concentrations of carotenoid pigments in the plasma and growing feather follicles of both captive and free-living cardinals. Compared to free-living cardinals, captive birds had significantly lower relative concentrations of red carotenoids in both follicles and plasma. The observation that, compared to free-living cardinals, captive male cardinals showed reduced production of red carotenoids with lower quantities in feather follicles supports the hypothesis that red coloration produced via the CYP2J19/BDH1L pathway is a condition-dependent trait. Red carotenoid-based coloration is widely recognized as a condition-dependent signal of quality that has been found to be sensitive to environmental challenges, but questions remain as to the specific effects of such challenges on mechanisms of red carotenoid production. Birds captured from the wild are under physiological challenge when held in captivity. We tested the hypothesis that the environmental challenge of captivity would cause Cardinalis cardinalis (Northern Cardinal) to grow feathers with lower concentrations of red ketocarotenoid pigments compared to birds growing feathers in the wild. Compared to cardinals molting in the wild, captive cardinals had lower levels of red ketocarotenoid pigments circulating in their blood with reduced concentrations in growing feathers. These observations support the hypothesis that the challenge of captivity inhibits expression of red coloration in C. Cardinalis. La coloraci & oacute;n basada en carotenoides es un ejemplo bien documentado de un rasgo dependiente de la condici & oacute;n, pero gran parte de la evidencia que respalda que la coloraci & oacute;n roja depende de la condici & oacute;n proviene de especies que pigmentan sus plumas principalmente con 3-hidroxiechinenona, un carotenoide rojo producido a partir de carotenoides amarillos de la dieta mediante una v & iacute;a metab & oacute;lica a & uacute;n desconocida. La dependencia de la condici & oacute;n del plumaje rojo en especies que utilizan las enzimas m & aacute;s comunes CYP2J19 y BDH1L para modificar carotenoides amarillos de la dieta en cetocarotenoides rojos ha sido menos estudiada. Evaluamos la hip & oacute;tesis de que el cautiverio afectar & iacute;a negativamente la producci & oacute;n de pigmentos rojos en machos de Cardinalis cardinalis, un paseriforme con extensa coloraci & oacute;n roja producida mediante la v & iacute;a CYP2J19/BDH1L. Confinamos en jaulas, durante la etapa de la muda, a un grupo de machos capturados en la naturaleza, utilizando el cautiverio como un desaf & iacute;o fisiol & oacute;gico, y los comparamos con cardenales en libertad. Proporcionamos a las aves en cautiverio abundante zeaxantina y lute & iacute;na, los pigmentos amarillos de la dieta que los cardenales convierten enzim & aacute;ticamente en los cetocarotenoides rojos astaxantina y alpha-doradexantina, para asegurar que una disponibilidad insuficiente de carotenoides no limitara la producci & oacute;n de pigmentos rojos. Durante la muda, medimos las concentraciones de pigmentos carotenoides en el plasma y en los fol & iacute;culos de plumas en crecimiento tanto de cardenales en cautiverio como de cardenales en libertad. En comparaci & oacute;n con los cardenales en libertad, las aves en cautiverio presentaron concentraciones relativas significativamente menores de carotenoides rojos tanto en los fol & iacute;culos como en el plasma. La observaci & oacute;n de que, en comparaci & oacute;n con los cardenales en libertad, los machos en cautiverio mostraron una producci & oacute;n reducida de carotenoides rojos y menores cantidades en los fol & iacute;culos de las plumas respalda la hip & oacute;tesis de que la coloraci & oacute;n roja producida mediante la v & iacute;a CYP2J19/BDH1L es un rasgo dependiente de la condici & oacute;n.

Super black plumage has been observed across the avian phylogeny, yet few studies have examined the prevalence of super black plumage at the species and subspecies levels. One group where additional super black taxa likely exist is manakins in the genus Lepidothrix. Previous work on these sexually dichromatic taxa showed that male Lepidothrix velutina (Velvety Manakins) have super black plumage, and we observed that males of several other Lepidothrix taxa have black plumage with a velvety appearance that is often associated with super black barbule morphologies. Here, we combine spectrophotometry with scanning electron microscopy to examine the occurrence of super black plumage throughout Lepidothrix. We determine how the barbules of super black taxa differ structurally from barbules of black taxa that lack super black plumage. Our results show that 5 species and 7 subspecies of Lepidothrix have super black plumage, that barbules of back feathers are wider and closer together in super black taxa than in black taxa, and that the super black plumage trait appears to have evolved multiple times independently in the genus. We also show that olive-green immature males of super black taxa exhibit wider barbules that are closer together than their counterparts, suggesting the development of super black plumage begins before males molt into their definitive adult plumage. Super black plumage has been reported across the avian phylogeny, but few studies have examined its occurrence at the species and subspecies levels. We measured reflectance, barbule width, interbarbule distance, and barbule angle in Lepidothrix manakins to examine the prevalence and causes of super black plumage throughout the genus. We found that 5 species and 7 subspecies of Lepidothrix have developed super black plumage, that super black plumage is associated with wider barbules that are closer together, and that the development of super black feathers begins before males reach their definitive adult plumage. The relatively short time spans during which super black plumage has evolved suggest the genetic mechanisms affecting this trait may be relatively simple. We show a previously unrecognized degree of variation in the reflectance and morphology of black feathers within a single bird genus, suggesting that additional studies of the occurrence of super black barbule morphologies across the bird Tree of Life are needed. Ao longo da filogenia de aves h & aacute; v & aacute;rias descri & ccedil;& otilde;es de plumagem super negra, no entanto poucos estudos examinaram a preval & ecirc;ncia dessa plumagem no n & iacute;vel de esp & eacute;cie e subesp & eacute;cie. Um grupo em que provavelmente h & aacute; t & aacute;xons com plumagem super negra ainda n & atilde;o descrita & eacute; o g & ecirc;nero Lepidothrix. Um estudo anterior com esses t & aacute;xons mostraram que o macho de Lepidothrix velutina apresenta plumagem super negra, e n & oacute;s observamos que outros machos de t & aacute;xons de Lepidothrix possuem plumagem preta com apar & ecirc;ncia de veludo, como & eacute; frequentemente descrita a plumagem super negra. Neste trabalho n & oacute;s combinamos dados de espectrofotometria e microscopia eletr & ocirc;nica de varredura para examinar a ocorr & ecirc;ncia de plumagem super negra em todo o g & ecirc;nero Lepidothrix. N & oacute;s determinamos como as b & aacute;rbulas de pena super negra diferem estruturalmente das b & aacute;rbulas de penas quem n & atilde;o tem cor super negra. Nossos resultados mostraram que cinco esp & eacute;cies e sete subesp & eacute;cies de Lepidothrix tem plumagem super negra, que b & aacute;rbulas s & atilde;o mais grossas e pr & oacute;ximas entre si na plumagem super negra do que nas penas que n & atilde;o s & atilde;o super negra, e que a plumagem super negra parece ter evolu & iacute;do m & uacute;ltiplas vezes independentes neste g & ecirc;nero. N & oacute;s tamb & eacute;m mostramos que machos juvenis imaturos com plumagem verde oliva possuem penas com b & aacute;rbulas intermedi & aacute;rias em grossura e proximidade uma das outras quando comparada com a morfologia de penas verde oliva de f & ecirc;meas e super negra de machos adultos. Este resultado sugere que o desenvolvimento da morfologia de pena super negra come & ccedil;a antes que os machos atingem a plumagem de adultos.