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Nicholas M. Masto, Abigail G. Blake-Bradshaw, Cory J. Highway, Allison C. Keever, Jamie C. Feddersen, Paul T. Link, Heath M. Hagy, Douglas C. Osborne, Bradley S. Cohen
KEYWORDS: Anas platyrhynchos, dynamic Brownian Bridge Movement Models, GPS telemetry, Mississippi Alluvial Valley, optimal migration, spring migration, regional habitat conservation, waterfowl, Anas platyrhynchos, modèles de mouvement dynamique à pont brownien, télémétrie GPS-GSM, vallée alluviale du Mississippi, migration optimale, migration printanière, conservation de l'habitat régional, compromis temps-énergie, sauvagine
Spring migration is hypothesized to be time-constrained because of competition for optimal nesting and brood-rearing sites. Therefore, individuals are predicted to minimize migration time to breeding destinations; however, migration strategies likely lie on a continuum based on wintering and stopover habitat quality, environmental conditions, or individual-level factors. In other words, individuals and wintering subpopulations may differentially prioritize time-energy trade-offs during migration depending on where they are from, when they leave, and where they are going. We tested these hypotheses by characterizing spatial and temporal variation in spring migration strategies in female Anas platyrhynchos (Mallards), using global positioning system (GPS) data from ∼150 individuals captured across the Mississippi Alluvial Valley and Gulf Coast Chenier Plain, USA. We used principal components analysis to classify a series of migratory behaviors into distinct time- and energy-minimization migration strategies, and tested whether migration strategies were related to wintering origins (habitat quality or latitudinal differences influencing migration initiation), migratory destinations (resource predictability), and individual-level factors (age and body condition). Additionally, we estimated individual and wintering subpopulation space-use to identify geographic regions of high and overlapping use that may facilitate time- or energy-minimizing migration strategies. Our results indicated a gradient of time-minimization migration strategies but migration strategy was not influenced by wintering origins nor migratory destination. Instead, time-energy trade-offs manifested at the individual level with time-minimization depending on experience and body condition. We also revealed stopovers and migration corridors of continental importance for spring-migrating A. platyrhynchos and space-use therein suggested migration strategies varied spatially with increasing time-minimization behavior as A. platyrhynchos neared their breeding grounds. Future research should link migration strategies and settling patterns to demographic rates.
LAY SUMMARY
Spring migration of Anas platyrhynchos (Mallard) is time-sensitive because individuals arriving earlier to the breeding grounds secure the best nesting sites. However, individuals must balance energy expenditure and food intake during long-distance migration.
We used GPS telemetry to investigate time-energy migration strategies and associated stopovers and migration routes of female Mallards captured during winter across the Mississippi Alluvial Valley and Gulf Coast Chenier Plains.
Despite latitudinal differences, A. platyrhynchos cohorts wintering in Louisiana, Arkansas, and Tennessee all migrated similarly quickly to the breeding grounds, suggesting internal and external cues prompted optimal departure timing. Instead, migration strategies varied at the individual level based on experience and body condition.
Migration corridors, core areas, and unique stopovers were identified for each A. platyrhynchos cohort. Concentrated stopovers, coupled with few stopovers for short durations, suggested these sites facilitated time-minimization migration by providing adequate food resources; however, these patterns varied spatially.
Future studies should explicitly examine stopover habitat quality and its effect on migration strategies, physiological condition, settling patterns, and reproductive success.
La migration printanière est présumée limitée dans le temps en raison de la compétition pour des sites optimaux de nidification et d'élevage des couvées. Par conséquent, les individus devraient limiter au minimum le temps de migration vers les destinations de reproduction. Cependant, les stratégies de migration se situent probablement dans un continuum basé sur la qualité de l'habitat d'hivernage et de halte, les conditions environnementales ou les facteurs individuels. En d'autres termes, les individus et les sous-populations hivernantes peuvent prioriser différemment les compromis de temps et d'énergie pendant la migration en fonction de leur origine, du moment de leur départ et de leur destination. Nous avons testé ces hypothèses en caractérisant la variation spatiale et temporelle des stratégies de migration printanière chez les femelles d'Anas platyrhynchos, en utilisant des données GPS d'environ 150 individus capturés dans la vallée alluviale du Mississippi et de la plaine de chêniers de la côte du golfe du Mexique, aux États-Unis. Nous avons utilisé l'analyse en composantes principales pour classifier une série de comportements migratoires en stratégies migratoires distinctes de minimisation du temps et de l'énergie, puis testé si les stratégies migratoires étaient liées aux origines d'hivernage (qualité de l'habitat ou différences latitudinales influençant le début de la migration), aux destinations migratoires (prédictibilité des ressources), et aux facteurs individuels (âge et condition corporelle). En outre, nous avons estimé l'utilisation de l'espace par les individus et la sous-population hivernante pour identifier les régions géographiques où l'utilisation est élevée et se chevauche, ce qui peut faciliter les stratégies migratoires minimisant le temps et l'énergie. Nos résultats ont indiqué un gradient de stratégies migratoires minimisant le temps, mais la stratégie migratoire n'était pas influencée par l'origine d'hivernage ni par la destination de migration. Au contraire, les compromis temps-énergie se sont manifestés au niveau individuel, la minimisation du temps dépendant de l'expérience et de la condition corporelle. Nous avons aussi découvert l'existence de haltes et de corridors de migration d'importance continentale pour A. platyrhynchos migrant au printemps, et l'utilisation de l'espace a suggéré que les stratégies migratoires variaient dans l'espace avec l'intensification du comportement minimisant le temps à mesure qu'A. platyrhynchos s'approchait des aires de reproduction. Les recherches futures devraient s'efforcer de relier les stratégies migratoires et les patrons d'établissement au taux démographique.
KEYWORDS: agonistic song, breeding success, nestling growth, Plasmodium, song duty cycle, song repertoire, Trypanosoma, piosenka odstraszająca, sukces rozrodczy, wzrost piskląt, Plasmodium, względny czas trwania śpiewu, wielkość repertuaru, Trypanosoma
The link between male song and reproductive success has been explored at length in socially monogamous birds, but results were inconsistent and under-represented socially non-monogamous species with uniparental care. Here, we evaluated whether metrics of male song in Acrocephalus paludicola (Aquatic Warbler), a promiscuous songbird with female-only care and large repertoires, are associated with fitness- and quality-related traits. We showed that the number of 9-day-old nestlings fathered and probability of avian malaria infection increased with the rate of agonistic song, produced in male–male interactions, and that male scaled mass index (proxy for energy reserves) positively correlated with the repertoire size. The male breeding success was not explained by repertoire size and song duty cycle. None of the song variables clearly explained the male return rate or change in the tarsus length (proxy for structural body size) and scaled mass index of the fathered chicks between days 2 and 9 post-hatch. No other relationships between the song characteristics and the inbreeding coefficient, scaled mass index, wing-length and Trypanosoma infection status of the males were supported, and Plasmodium infection was unrelated to the song duty cycle and repertoire size. We conclude that in male A. paludicola the repertoire size could be a signal of early developmental stress or current body condition, and the agonistic song rate could be shaped by sexual selection and signal to females a genetic makeup that enhances survival upon infection by Plasmodium.
LAY SUMMARY
Elaborate song in male songbirds is believed to have evolved because song complexity promoted reproduction success.
This concept has not received firm support, and songbirds with female-only care over young remain understudied.
In Acrocephalus paludicola (Aquatic Warbler), a songbird with female-only care, males that more frequently sang aggressive songs used to deter other males had more nestlings and were more likely to contract avian malaria, and males with more diverse song were in better condition.
Male A. paludicola with higher aggressive song rates might be favored by natural selection.
Song diversity could be affected by conditions at rearing or current health.
Agonistic song of male A. paludicola could signal to females traits that enhance survival of avian malaria-infected males.
U samców ptaków zależność między śpiewem a sukcesem reprodukcyjnym badano szczegółowo u monogamistów socjalnych. Wyniki były jednak niespójne i rzadko badano gatunki niebędące monogamistami socjalnymi, u których występuje jednorodzicielska opieka nad potomstwem. W naszej pracy określiliśmy, czy u wodniczki Acrocephalus paludicola, promiskuitycznego gatunku ptaka śpiewającego o złożonej piosence, u którego potomstwem opiekuje się tylko samica, elementy śpiewu samców są powiązane z miarami ich dostosowania i jakości. Wykazaliśmy, że liczba spłodzonych 9-dniowych piskląt i prawdopodobieństwo wystąpienia ptasiej malarii wzrastały wraz z tempem produkcji piosenek odstraszających, śpiewanych w interakcjach z innymi samcami. Wskaźnik skalowanej masy ciała samców (określający ilość rezerw energetycznych) był dodatnio skorelowany z wielkością repertuaru. Sukces rozrodczy samców nie był wyjaśniony przez wielkość repertuaru ani względny czas trwania śpiewu. Żadna z badanych cech śpiewu nie była wyraźnie związana z powracalnością samców na lęgowiska, ani też zmianą długości skoku (określającego strukturalną wielkość ciała) i skalowanego wskaźnika masy ciała spłodzonych piskląt między 2. a 9. dniem od wyklucia. Nie stwierdziliśmy żadnych innych zależności między badanymi cechami śpiewu samców a ich współczynnikiem wsobności, skalowanym wskaźnikiem masy ciała, długością skrzydła ani też zakażeniem Trypanosoma. Zakażenie Plasmodium nie było powiązane z względnym czasem trwania śpiewu ani z wielkością repertuaru. Wyniki te wskazują, że u samców wodniczek wielkość repertuaru może nieść informację o poziomie stresu wczesnorozwojowego lub o ich bieżącej kondycji. Tempo śpiewu piosenek odstraszających może podlegać działaniu doboru płciowego i stanowić dla samic informację o posiadaniu przez samca genów zwiększających szanse przeżycia po zakażeniu Plasmodium.
We found a stable pattern of geographic variation in songs across the breeding range of the Geothlypis philadelphia (Mourning Warbler) over a 36-year period. The Western, Eastern, Nova Scotia, and Newfoundland regiolects found in 2005 to 2009 also existed in 1983 to 1988 and 2017 to 2019. Each regiolect contained a pool of syllables that were unique and different from the other regiolects. The primary syllable types that defined each regiolect were present throughout the study, but there were changes in the frequencies of variants of these syllable types in each regiolect. We developed an agent-based model of birdsong learning within each regiolect to explore whether these frequency changes were consistent with unbiased copying or 2 forms of transmission bias: frequency bias and content bias. Strong content bias, possibly for more complex syllables, best models the temporal dynamics across regiolects. In combination with a high estimated learning fidelity, this may explain why regiolects and syllable types were stable for 36 years. We also examined whether variation in physical parameters of song over time could be attributed to acoustic adaptation to breeding habitat, using Landsat variables as a proxy for vegetation characteristics of each male's breeding territory. The physical parameters of the songs, which changed little over time, revealed no coherent relationships with the Landsat variables and therefore little evidence for acoustic adaptation.
LAY SUMMARY
We studied changes in Geothlypis philadelphia (Mourning Warbler) songs, syllables, and physical parameters of songs from 3 time periods throughout the breeding range: 1983 to 1988, 2005 to 2009, and 2017 to 2019.
We found that the same pattern of geographic variation in songs existed in each time period.
The stability may be due to strong content bias where birds in different regions of the breeding range preferred to learn certain syllable types unique to each region.
Physical parameters of song also remained largely unchanged over the study period.
Song parameters were not selected for optimal transmission through the breeding habitat.
Nous avons trouvé un patron stable de variation géographique des chants dans l'aire de reproduction de Geothlypis philadelphia sur une période de 36 ans. Les régiolectes de l'Ouest, de l'Est, de Nouvelle-Écosse et de Terre-Neuve trouvés en 2005 to 2009 existaient également en 1983 to 1988 et en 2017 to 2019. Chaque régiolecte contenait un ensemble de syllabes uniques et différentes des autres régiolectes. Les principaux types de syllabes qui définissaient chaque régiolecte étaient présents tout au long de l'étude, mais les fréquences des variantes de ces types de syllabes ont changé dans chaque régiolecte. Nous avons développé un modèle à base d'agents d'apprentissage de chants d'oiseaux au sein de chaque régiolecte afin d'explorer si ces changements de fréquence étaient cohérents avec une imitation non biaisée ou avec deux formes de biais de transmission: le biais de fréquence et le biais de contenu. Un fort biais de contenu, possiblement pour des syllabes plus complexes, modélise le mieux la dynamique temporelle dans les régiolectes. En combinaison avec une fidélité d'apprentissage élevée, cela peut expliquer pourquoi les régiolectes et les types de syllabes sont restés stables pendant 36 ans. Nous avons aussi examiné si la variation temporelle des paramètres physiques du chant pouvait être attribuée à l'adaptation acoustique par rapport à l'habitat de reproduction, en utilisant les variables Landsat comme indicateur des caractéristiques de végétation du territoire de reproduction de chaque mâle. Les paramètres physiques des chants, qui ont peu changé au fil du temps, n'ont révélé aucune relation cohérente avec les variables Landsat et donc peu de preuves d'une adaptation acoustique.
Sarah Guindre-Parker, Arianna Acosta, Cole Bourque, Amberlee Cook, Joanna Corimanya, Rachel Kaplan, Denyelle AV Kilgour, Courtney R. Linkous, Michelle Ross, Trinity Smith, Careyjo Titus
Species classified as “urban-adapters” are often assumed to thrive in cities because they are commonly found across the urbanization gradient. However, urban-living populations of many urban-adapted species have been found to have lower reproductive success relative to their rural counterparts. Sturnus vulgaris (European Starling) is a common urban-adapted species found across most of the globe. While S. vulgaris have lowered reproductive success in urban areas in their native range, less is known about how urbanization impacts reproduction in their invasive ranges. We tested for differences in reproductive investment and success across urban and rural S. vulgaris populations in Georgia, which is part of their North American invasive range. We found few differences in reproductive output for urban vs. rural S. vulgaris—clutch size, egg mass, egg volume, incubation behavior, provisioning rates, brooding behavior, and nestling wing chord were all similar across S. vulgaris populations from more urban and more rural study sites. Although urban birds produced a higher number of hatchlings and rural birds produced young in higher body condition, neither of these factors influenced reproductive success because the number of fledglings produced were similar for urban and rural breeding S. vulgaris. Overall, S. vulgaris in their invasive range performed similarly well in more urban vs. more rural habitats. Future work should explore whether urbanization affects other components of fitness in starlings (e.g., adult survival).
Birds living in urban centers can sometimes produce fewer chicks in their nests, though it is not always clear why.
We monitored nests of a common bird—Sturnus vulgaris (European Starling)—at 2 urban and 2 rural sites in metro Atlanta, Georgia, USA.
We counted (1) the number of eggs in each nest, egg mass, and volume, as well as the amount of time parents spent keeping their eggs warm; (2) the number of nestlings that hatched in each nest, their wing length, and body condition, as well as the amount of food the parents delivered to the nest; and (3) the number of nestlings that fledged each nest successfully.
While we expected nests from urban sites to have fewer or smaller eggs and nestlings, we found that rural and urban nests were statistically the same with a few exceptions. Urban S. vulgaris hatched more of their eggs into nestlings, and rural birds had nestlings in superior body condition.
Ultimately, because urban and rural nests had the same number of chicks surviving to the age of leaving the nest, it appears that S. vulgaris breed similarly well in urban and rural areas in metro Atlanta.
We suggest that future studies could look at where chicks choose to live or breed in the future, as well as how urban life affects adult condition and survival rather than just nestlings.
Les espèces classées comme « adaptées à la ville» sont souvent présumées prospérer dans les villes parce qu'elles sont communément observées sur tout le gradient d'urbanization. Cependant, on a constaté que les populations urbaines de nombreuses espèces adaptées à la ville ont un succès reproductif inférieur à celui de leurs congénères ruraux. Sturnus vulgaris est une espèce commune adaptée à la ville que l'on trouve dans la plupart des régions du monde. Alors que S. vulgaris a un succès reproductif plus faible dans les zones urbaines de son aire de répartition naturelle, on en sait moins sur la façon dont l'urbanization affecte la reproduction dans ses aires de répartition invasives. Nous avons testé les différences d'investissement et de succès reproductif entre les populations urbaines et rurales de S. vulgaris en Géorgie, qui fait partie de son aire de répartition invasive en Amérique du Nord. Nous avons trouvé peu de différences dans les paramètres de reproduction de S. vulgaris en milieu urbain et en milieu rural: la taille de couvée, la masse des œufs, le volume des œufs, le comportement de couvaison des œufs, le taux de nourrissage, le comportement de couvaison des jeunes et la corde de l'aile des oisillons étaient tous similaires dans les populations de S. vulgaris des sites d'étude les plus urbains et les plus ruraux. Bien que les oiseaux urbains aient produit un plus grand nombre d'oisillons à l'éclosion et que les oiseaux ruraux aient produit des jeunes en meilleure condition physique, aucun de ces facteurs n'a influencé le succès reproductif car le nombre d'oisillons à l'envol produits était similaire pour S. vulgaris se reproduisant en milieu urbain et en milieu rural. Dans l'ensemble, S. vulgaris a eu un succès similaire dans les habitats plus urbains et les habitats plus ruraux de son aire de répartition invasive. Les futures recherches devraient explorer si l'urbanization affecte d'autres composantes de la condition physique chez cette espèce (p. ex., la survie des adultes).
Seasonally declining reproductive performance in avian populations may be attributed to high-quality individuals breeding earlier than low-quality individuals (the quality hypothesis), to deteriorating environmental conditions (the date hypothesis), or both. By comparing the reproductive performance among different perennial pairs, and the same perennial pairs across different years, we tested the influence of timing of breeding on reproductive performance in Dicrurus hottentottus (Hair-crested Drongo) from 2010 to 2022. Breeding pairs that typically laid earlier relative to the population mean (i.e., early-breeding pairs) exhibited a significantly higher fledging rate compared to breeding pairs that often bred later relative to the population mean (i.e., late-breeding pairs). For a given pair, the fledging rate of early-breeding pairs increased when they bred later compared to other years, while the fledging rates of late-breeding pairs were significantly lower in years when they bred later than usual. We found that male morphological traits were associated with both the timing of breeding and the feeding rate. Pairs with long-billed (indicator of high quality) males bred earlier than pairs with short-billed males, and pairs with larger males (indicator of high quality) had a higher feeding rate than pairs with smaller males. Female age had reversed effects on the timing of breeding and fledging rate: older females tended to breed earlier than younger females; but there was a sharp decline in fledging rate after 7 years of age in late-breeding pairs. Finally, our results showed that the feeding rate and the amount of invertebrate biomass decreased with laying date, indicating deteriorating feeding conditions later in the breeding season. Overall, our findings support both the quality hypothesis and the date hypothesis. Low-quality D. hottentottus are likely to be most adversely affected by the phenological mismatches induced by climate change, which, in turn, may affect population dynamics through reduced fecundity.
LAY SUMMARY
We compared the reproductive success of the same perennial pairs in different years to examine how the timing of breeding affects reproductive performance.
The fledging rate of Dicrurus hottentottus (Hair-crested Drongo) decreased temporally over the breeding season, and this trend was consistent among most years.
Early-breeding and late-breeding pairs exhibited respectively higher and lower fledging rates in years when they bred later than usual.
Individuals possessing indicators of quality bred earlier and had higher feeding rates.
Both the amount of invertebrate biomass and feeding rate were reduced later in the breeding season.
Our results support both the quality hypothesis and the date hypothesis, which explain the mechanism behind the temporal decline in reproductive performance.
KEYWORDS: Acrocephalus sechellensis, cooperative breeding, nest predation, nest-site selection, Seychelles Warbler, territory quality, Acrocephalus sechellensis, reproduction coopérative, prédation du nid, sélection du site de nidification, qualité du territoire
Nest-site selection is an important determinant of avian reproductive success, mainly through its effect on predation risk. However, which environmental and social factors affect nest-site selection and predation risk remains less well understood. Optimal nest positioning may depend on the balance of many distinct factors such as nest predation, food availability, extra-pair mating opportunities, presence of helpers, and interactions with neighboring conspecifics. We investigated how these factors affect nest-site selection and nest survival in Acrocephalus sechellensis (Seychelles Warbler), a facultative cooperative-breeding passerine that defends stable territories year-round. We found that daily nest survival increased by ∼1% for each meter higher in the canopy that a nest was placed. Nests were more likely to be located in food-rich parts of the territory, especially in territories with low overall densities of arthropods. Further, we found that nests in territories with helpers, which reduce nest predation in A. sechellensis, were built in areas with higher food availability, whereas nests in territories without helpers were built in areas with fewer nest predators. Finally, we found that females build their nests 0.5 m closer to the border for each year the nearest neighboring male was older than their partner. Our results suggest that nest-site selection in A. sechellensis is affected by nest predation, food availability, helper presence, and possibly, the female's opportunity for extra-pair copulations. Clarifying the relative importance of these different selective factors is key to the understanding of optimal nest-site selection to maximize reproductive success.
LAY SUMMARY
Acrocephalus sechellensis (Seychelles Warbler) built nests in areas with fewer nest predators, in higher canopy, with higher food abundance, closer to potential extra-pair mates, and had a preference for specific tree species.
Breeders that were assisted by helping subordinates built their nest in areas with higher food availability, whereas nests in territories without helpers were built in areas with fewer nest predators. Because helpers reduce nest predation, pairs with helpers may be more flexible with respect to their choice of nest location and nest in areas with higher food availability, whereas pairs without helpers may be more selective about nesting in areas with lower predator density.
Females placed their nest closer to the territory border if the nearest neighboring male was older than her partner, possibly as a means to gain genetic benefits through extra-pair paternity.
Higher nest height relative to the mean canopy-top height in a territory was associated with higher nest survival rates.
La sélection du site de nidification est un facteur important du succès reproducteur chez les oiseaux, principalement par son effet sur le risque de prédation. Cependant, les facteurs environnementaux et sociaux qui influencent la sélection du site de nidification et le risque de prédation restent moins bien compris. Le positionnement optimal du nid peut dépendre de l'équilibre de plusieurs facteurs distincts comme la prédation du nid, la disponibilité de la nourriture, les occasions d'accouplement hors couple, la présence d'aides parentales et les interactions avec les congénères voisins. Nous avons étudié comment ces facteurs influencent la sélection du site de nidification et la survie du nid chez Acrocephalus sechellensis, un passereau dont la reproduction est facultativement coopérative et qui défend des territoires stables à l'année. Nous avons constaté que la survie quotidienne des nids augmente d'environ 1 % pour chaque mètre plus haut dans la canopée qu'un nid était placé. Les nids étaient plus susceptibles d'être situés dans des parties du territoire riches en nourriture, particulièrement dans les territoires ayant des densités globalement faibles d'arthropodes. De plus, nous avons constaté que les nids dans les territoires avec des aides parentales, lesquelles réduisent la prédation des nids chez A. sechellensis, étaient construits dans des zones avec une plus grande disponibilité en nourriture, alors que les nids dans les territoires sans aides parentales étaient construits dans des zones ayant moins de prédateurs de nids. Enfin, nous avons constaté que les femelles construisent leurs nids 0.5 m plus près des lisières à chaque année où le mâle voisin le plus près était plus âgé que leur propre partenaire. Nos résultats suggèrent que la sélection du site de nidification chez A. sechellensis est affectée par la prédation du nid, la disponibilité de la nourriture, la présence d'aides parentales et, possiblement, par l'opportunité pour la femelle d'avoir des copulations extra-conjugales. La clarification de l'importance relative de ces différents facteurs sélectifs est essentielle pour comprendre la sélection du site de nidification optimal permettant de maximiser le succès reproducteur.
The West Indies is considered a biodiversity hotspot and a priority for ecological conservation efforts. Understanding how environmental conditions influence the survival of resident avifauna is an important information need given the predicted increases in drought and the frequency and intensity of severe storms in the region. Throughout much of the Caribbean, Coereba flaveola (Bananaquit) are widespread and abundant, traits that may facilitate understanding their response to environmental changes in the region. We used a 10-yr capture–mark–recapture data set to examine C. flaveola survival, recruitment, population growth, and age structure in the context of monthly and seasonal precipitation and temperatures, drought conditions, and occurrence and intensity of storm events. Our models suggested wing length, occurrence of storms, and drought all influenced survival. Both the incidence of storms and drier-than-average conditions in the preceding wet season (April–June) decreased survival. The sex of bird and net hours influenced capture probability, but weather influences on recruitment were equivocal. During nonstorm years, mean population growth was stable at 1.019 (95% confidence interval [CI]: 0.962, 1.098) but dropped to 0.843 (95% CI: 0.795, 0.846) in storm years. Increasing frequency of storms, such as back-to-back years, would likely push the growth rate lower. A protracted pattern of increased storm frequency, especially if coupled with a subsequent drought during the wet season, may lead to localized extirpations or strongly reduced populations.
LAY SUMMARY
Ten years of mark–recapture data were used to assess weather and climate factors influencing the survival of Coereba flaveola (Bananaquit).
Models suggested the size of the bird, occurrence of storms, and wet season (April–June) rainfall all influenced survival.
During nonstorm years, population growth was nearly stable but declines occurred in storm years.
A protracted pattern of increased storm frequency, especially if coupled with a subsequent dry wet season, may lead to localized extirpations or strongly reduced populations.
Las Indias Occidentales se consideran un punto crítico de biodiversidad y una prioridad para los esfuerzos de conservación ecológica. Comprender cómonth las condiciones ambientales influyen en la supervivencia de la avifauna residente es una necesidad de información importante dado el aumento pronosticado de la sequía y la frecuencia e intensidad de tormentas severas en la región. En gran parte del Caribe, Coereba flaveola es una especie extendida y abundante, características que pueden facilitar la comprensión de su respuesta a los cambios ambientales en la región. Usamos un conjunto de datos de captura-marcado-recaptura de 10 años para examinar la supervivencia, el reclutamiento, el crecimiento poblacional y la estructura de edad de C. flaveola en el contexto de precipitaciones y temperaturas mensuales y estacionales, condiciones de sequía y la ocurrencia e intensidad de eventos de tormenta. Nuestros modelos sugirieron que la longitud del ala, la ocurrencia de tormentas y la sequía influyeron en la supervivencia. Tanto la incidencia de tormentas comonth las condiciones más secas de lo normal en la temporada húmeda anterior (abril-junio) redujeron la supervivencia. El sexo del ave y las horas de red influyeron en la probabilidad de captura, pero las influencias climáticas en el reclutamiento fueron ambiguas. Durante los años sin tormentas, el crecimiento poblacional medio fue estable en 1.019 (IC del 95%: 0.962, 1.098), pero cayó a 0.843 (IC del 95%: 0.795, 0.846) en los años con tormentas. El aumento de la frecuencia de tormentas, comonth en años consecutivos, probablemente reduciría aún más la tasa de crecimiento. Un patrón prolongado de aumento de la frecuencia de tormentas, especialmente si se combina con una sequía subsecuente durante la temporada húmeda, podría llevar a extirpaciones localizadas o poblaciones fuertemente reducidas.
Climate warming is affecting the phenology and life history of animals around the world. In birds, although warm winters have been shown to advance breeding dates and affect reproductive success in a diverse range of taxa, few studies document whether changes in breeding phenology are associated with variability in reproductive effort by breeders. We leveraged a 37-year dataset on the demography of Aphelocoma coerulescens (Florida Scrub-Jay) to investigate not only whether winter weather affects scrub-jay phenology and reproductive success, but also whether winter weather affects overall reproductive effort. Scrub-jays bred early but fledged fewer offspring in springs following warm winters. Surprisingly, this reduced reproductive success came at the expense of increased reproductive effort (number of nests built, number of eggs laid, and length of the breeding period across all attempts) by the breeders. Given the well-known trade-off between reproductive effort and survival, we highlight an important but typically unrecognized cost of climate warming on birds, as revealed by a long-term study of a large, well-protected population.
LAY SUMMARY
Several species are responding to warming climates by advancing or delaying their nesting phenology.
These changes may increase, decrease, or not change the reproductive success for individuals. Given that individual survival is often negatively associated with breeding effort, it is important to measure the reproductive effort invested by individuals in relation to their reproductive success to fully understand the effects of climate change.
We used a 37-year long-term dataset on the demography of the federally Threatened Aphelocoma coerulescens (Florida Scrub-Jay) to show that warm winters led to scrub-jays having advanced lay dates and lower reproductive success (number of fledglings) while simultaneously increasing reproductive effort (number of nests built, number of eggs laid, and length of breeding season).
Our research highlights a critical but seldom quantified effect of climate change on the annual reproductive effort in birds. How increased reproductive effort may affect individual survival remains to be studied.
El calentamiento climático está afectando la fenología y la historia de vida de los animales en todo el mundo. En las aves, aunque se ha demostrado que los inviernos cálidos adelantan las fechas de reproducción y afectan el éxito reproductivo en una amplia gama de taxones, pocos estudios documentan si los cambios en la fenología reproductiva están asociados con la variabilidad en el esfuerzo reproductivo por parte de los reproductores. Aprovechamos un conjunto de datos de 37 años sobre la demografía de Aphelocoma coerulescens para investigar no solo si el clima invernal afecta la fenología y el éxito reproductivo de esta especie, sino también si el clima invernal afecta el esfuerzo reproductivo general. Los individuos de A. coerulescens criaron temprano, pero emplumaron menos crías en las primaveras que siguieron a inviernos cálidos. Sorprendentemente, este éxito reproductivo reducido se dio a expensas de un mayor esfuerzo reproductivo (número de nidos construidos, número de huevos puestos y duración del período de cría en todos los intentos) por parte de los reproductores. Dada la conocida disyuntiva entre el esfuerzo reproductivo y la supervivencia, destacamos un costo importante pero típicamente no reconocido del calentamiento climático en las aves, como lo revela un estudio a largo plazo de una población grande y bien protegida.
Predators may adjust their diets to match their energy needs and food availability, but these adjustments have not been explored for migratory aerial insectivores outside of the breeding grounds. We found that Chordeiles minor (Common Nighthawk), a long-distance migrant and member of the rapidly declining aerial insectivore guild, exhibited similar levels of diet richness, diet diversity, and prey selectivity on the breeding and nonbreeding grounds, despite large differences in prey abundance. We examined the diets and prey communities of C. minor during 2 breeding seasons in Florida, USA, and 2 nonbreeding seasons in Corrientes Province, Argentina (2020 to 2022). We used DNA metabarcoding to identify insect prey in C. minor fecal samples, and we employed Malaise and UV light traps to assess abundance and composition of aerial insect prey communities. Abundance and richness of available prey were significantly higher on the nonbreeding grounds than on the breeding grounds. Even so, C. minor exhibited similar within-sample and within-population diet richness, Shannon and Simpson diversities, and prey preferences at both sites. Adults differed in their consumption of Lepidoptera between sites: adults on the nonbreeding grounds preferred Lepidoptera over all other orders, whereas adults on the breeding grounds consumed Lepidoptera less frequently than expected. We suggest that breeding adult C. minor may deliver Lepidoptera to their young instead of consuming this prey. At both sites, C. minor showed preference for Hemiptera and Hymenoptera–both large-bodied, nutrient-rich prey–suggesting that these generalist predators exhibit less diet flexibility than previously thought and thus may be vulnerable to changes in prey communities at multiple points in the annual cycle.
LAY SUMMARY
Predators that adjust their diets to match energy needs and prey abundances may be less vulnerable to changes in prey availability than predators lacking dietary flexibility.
We used DNA metabarcoding and aerial insect sampling to evaluate the diet diversity and prey selection of Chordeiles minor (Common Nighthawk) on their breeding grounds in the United States and nonbreeding grounds in Argentina.
The abundance, richness, and diversity of available prey differed between sites, but C. minor diet diversity and richness did not differ.
Diets were dominated by Hemiptera and Hymenoptera, which were consumed more than expected by their relative availability.
Chordeiles minor consumed Lepidoptera more than expected on nonbreeding grounds, but less than expected on the breeding grounds, where they may have chosen to give Lepidoptera to their young.
Our results suggest that C. minor could be vulnerable to changes in insect communities on both the breeding and nonbreeding grounds.
Los depredadores pueden ajustar sus dietas para satisfacer sus necesidades energéticas o disponibilidad de alimentos, pero no se ha explorado estos ajustes en insectívoros aéreos migratorios fuera de sus zonas de reproducción. Encontramos que C. minor (el añapero boreal), un migrante de larga distancia y miembro del gremio de insectívoros aéreos en rápido declive, presentó niveles similares de riqueza de la dieta, diversidad de la dieta y selectividad de presas en las zonas reproductivas y las no reproductivas. Examinamos las dietas y las comunidades de presas de C. minor durante dos temporadas de cría en Florida, EE.UU., y dos temporadas no reproductivas en la provincia de Corrientes, Argentina (2020–2022). Utilizamos metabarcoding de ADN para identificar insectos en muestras fecales de C. minor, y empleamos trampas malaise y de luz UV para evaluar la abundancia y la composición de las comunidades de presas (insectos aéreos). La abundancia y riqueza de presas disponibles fueron significativamente mayores en las zonas no reproductivas que en las reproductivas. Aún así, C. minor mostró una riqueza de dieta, diversidades de Shannon y Simpson y preferencias de presas (dentro de cada muestra y dentro de la población) similares entre ambos sitios. Los adultos diferían en su consumo de lepidópteros entre sitios: los adultos de las zonas no reproductivas prefirieron los lepidópteros a todos los demás órdenes, mientras que los adultos de las zonas reproductivas consumieron lepidópteros con menos frecuencia de lo esperado. Sugerimos que los adultos reproductores pueden entregar lepidópteros a sus crías en lugar de consumirlos. En ambas estaciones, C. minor mostró preferencia por presas de gran tamaño y ricas en nutrientes, lo que sugiere que estas aves generalistas muestran menos flexibilidad en su dieta de lo que se pensaba y podrían ser, por tanto, vulnerables a los cambios en las comunidades de presas en múltiples etapas del ciclo anual.
KEYWORDS: automated telemetry, full annual cycle ecology, migration, Motus wildlife tracking network, ecología del ciclo anual completo, migración, red de seguimiento de vida silvestre Motus, telemetría automatizada
Rarely, is there an opportunity to study and directly observe the same migratory animal across both breeding and nonbreeding seasons. In a rare, documented case, we highlight a live reencounter of a female Setophaga ruticilla (American Redstart) on its nest during the breeding season—an individual that was originally captured and tagged on its nonbreeding territory in Jamaica more than 3,250 km away. Advances in tracking technology allow researchers to track the movements of smaller organisms at higher resolutions. While tracking data alone have provided critical advances in the ecology of migratory animals, especially small migratory birds, there are exciting opportunities to move beyond tracking and to deeply explore biological questions about migratory animals by locating and directly studying (e.g., direct observation and physical sampling) the same individuals across the year. Although we have had the ability to precisely track large-bodied migratory birds (>100 g) for decades, researchers have rarely used these data to localize and directly observe or sample them across the year. Ultimately, we must consider the potential advances to be made in avian ecology through this endeavor. To this end, we highlight several specific areas of research that we believe move beyond tracking and can only be addressed by integrating direct longitudinal studies of individuals.
LAY SUMMARY
Here, we document a rare observation of a female Setophaga ruticilla (American Redstart) on her nest in northern Wisconsin that was originally captured and tagged on her nonbreeding territory in Jamaica more than 3,250 km away.
As technology evolves and our ability to track smaller migrants for longer durations rapidly improves, these live reencounters will continue to become more common.
Although tracking data alone provide critical advances in the ecology of migratory birds, we highlight several areas of research that we believe can only be addressed by directly studying and observing individuals repeatedly across the year.
These longitudinal data will allow us to dive deeper into the ecology of migrants transforming our understanding of everything from individual behavior and physiology to population ecology and conservation.
This single S. ruticilla observation serves as a timely reminder of the opportunities that in-depth longitudinal studies will provide toward ushering in new perspectives on longstanding issues and concepts long held as true in ornithology.
Rara vez existe la oportunidad de estudiar y observar directamente al mismo animal migratorio tanto en las temporadas reproductivas como en las no reproductivas. En un caso raro y documentado, destacamos el reencuentro en vivo de una hembra de Setophaga ruticilla en su nido durante la temporada reproductiva—un individuo que fue originalmente capturado y marcado en su territorio no reproductivo en Jamaica, a más de 3.250 kilómetros de distancia. Los avances en la tecnología de seguimiento están permitiendo a los investigadores rastrear los movimientos de organismos cada vez más pequeños con resoluciones más altas. Aunque los datos de seguimiento por sí solos están proporcionando avances críticos en la ecología de los animales migratorios, especialmente las aves migratorias pequeñas, existen oportunidades emocionantes para ir más allá del seguimiento y explorar con profundidad preguntas biológicas sobre los animales migratorios al localizar y estudiar directamente (e.g., observación directa y muestreo físico) a los mismos individuos a lo largo del año. Aunque hemos tenido la capacidad de rastrear con precisión a aves migratorias de gran tamaño (>100 g) durante décadas, rara vez los investigadores han utilizado estos datos para localizar y observar o muestrear directamente a estas aves a lo largo del año. En última instancia, debemos considerar los avances potenciales que se pueden lograr en la ecología aviar a través de este esfuerzo. Con este fin, destacamos varias áreas específicas de investigación que creemos van más allá del seguimiento y que solo pueden abordarse integrando estudios longitudinales directos de individuos.
Despite the role of many domestic animals as model organisms, our understanding of their undomesticated conspecifics is comparatively poor. This limits our ability to infer the eco-evolutionary context of phenomena studied in the laboratory and to explore domestication. The domestic pigeon's wild form is the Rock Dove (Columba livia). By studying 5 global positioning system–tagged wild Rock Doves in Scotland's Outer Hebrides, we present the first individual-level assessment of undomesticated Rock Dove movements, revealing extensive use of anthropogenic habitats in both a roosting and foraging context. This association with humans provides tantalizing opportunities for research into the pre-domestication human–pigeon relationship. More generally, this work highlights the value of researching laboratory model species in nature.
LAY SUMMARY
Despite the importance of laboratory model organisms, our understanding of their wild forms is comparatively poor.
Researching the wild forms of model organisms could enhance our understanding of the ecological and evolutionary context of phenomena studied in captivity.
Here we describe individual-level movements of Rock Doves (Columba livia), the wild form of domestic pigeons (a model organism in behavioral research).
We outline the movements of 5 global positioning system–tagged birds from Scotland's Outer Hebrides, where Rock Doves rarely interbreed with domestic pigeons.
We show that all individuals were closely associated with humans in both a roosting and foraging context, providing insights into this species' pathway into domestication.
Malgré le rôle de plusieurs animaux domestiques comme organismes modèles, notre compréhension de leurs congénères non domestiqués est assez limitée. Cela limite notre capacité à déduire le contexte éco-évolutif des phénomènes étudiés au laboratoire et à explorer la domestication. La forme sauvage du pigeon domestique est le pigeon biset (Columba livia). En étudiant 5 individus sauvages de C. livia marqués par GPS dans les Hébrides extérieures écossaises, nous présentons la première évaluation au niveau individuel des mouvements de C. livia non domestiqué, révélant une utilisation extensive d'habitats anthropiques dans des contextes de repos et de recherche alimentaire. Cette association avec les humains offre des opportunités intéressantes pour la recherche sur la relation homme-pigeon avant la domestication. Plus généralement, ce travail met en évidence la valeur de la recherche sur les espèces modèles de laboratoire dans la nature.
KEYWORDS: Chaco, foraging techniques, nest-site selection, wood hardness, woodpecker, Chaco, técnicas de forrajeo, selección de sitios de nidificación, dureza de la madera, pájaros carpinteros
Avian excavators (woodpeckers and other species) select nest sites based on the characteristics of the nest patch, nest tree, and substrate. These characteristics could increase foraging opportunities or reduce the risk of predation, but there is also a potentially important role for wood hardness in restricting nest-site selection, a role that has been little explored and is expected to vary among species according to their ability to excavate. We examined patterns of nest-site selection in 8 woodpecker species in the humid Chaco of South America, where the dominant trees have extremely hard wood. We hypothesized that (1) wood hardness is the main factor driving the selection of excavation sites, and (2) interspecific variation in body size and foraging behavior (traits frequently related to excavation ability) explain interspecific variation in the wood hardness of excavated nest substrates. From 2016 to 2019 in well-preserved forests of the Argentine Chaco, we compared nesting cavities excavated in wood (cases; n = 42) vs. potential wood substrates without cavities (matched controls) and made 187 focal observations of foraging woodpeckers. Woodpeckers selected nesting substrates with softer heartwood than potential substrates, regardless of any other characteristics of the tree or nest patch. Wood hardness around nest cavities increased with body size and the prevalence of chiseling during foraging, traits that were positively correlated. Woodpeckers often excavated in Prosopis spp. (Algarrobos) but rarely in Schinopsis balansae (Quebracho), a tree with exceptionally hard internal wood, in which cavity adopters frequently nest in non-excavated cavities. Wood hardness is critical to assessing the role of woodpeckers as cavity facilitators, understanding the costs and benefits of excavation, and interpreting excavation patterns across species and forests globally.
LAY SUMMARY
Wood hardness is an understudied but potentially restrictive aspect of nest-site selection for cavity-excavating birds.
We studied nest-site selection in 8 woodpecker species in the humid Chaco of South America, where the dominant trees have extremely hard wood.
We predicted that factors related to substrate suitability would be more influential in nest-site selection than factors related to nest survival.
Wood hardness restricted nest-site selection by woodpeckers.
Large woodpecker species, which foraged mainly by chiseling, excavated their nests in harder wood than smaller species that foraged by gleaning.
Woodpeckers rarely excavated in Schinopsis balansae (Quebracho), a tree with exceptionally hard internal wood, in which cavity adopters frequently nest in non-excavated cavities.
An understanding of wood hardness is key to interpreting relationships among species of cavity-nesting birds.
Las aves excavadoras de cavidades (pájaros carpinteros y otras especies) seleccionan sitios de nidificación basándose en características del parche de nidificación, el árbol nido y el sustrato. Estas características podrían aumentar las oportunidades de forrajeo o reducir el riesgo de la depredación, pero la dureza de la madera también juega un papel importante en restringir la selección de sitios, un aspecto poco explorado y que se espera varíe entre especies según su capacidad de excavación. Examinamos los patrones de selección de sitios de nidificación en ocho especies de pájaros carpinteros en el Chaco húmedo de Sudamérica, donde los árboles dominantes tienen una madera extremadamente dura. Hipotetizamos que 1) la dureza de la madera es el factor principal en la selección de sitios para excavar, y 2) la variación interespecífica en el tamaño corporal y los comportamientos de forrajeo (rasgos frecuentemente relacionados con la capacidad de excavación) explican la variación interespecífica en la dureza de la madera excavada en los sustratos de nidificación. De 2016 a 2019 en bosques bien conservados del chaco argentino, comparamos cavidades-nidos excavadas en árboles (casos; n = 42) vs. sustratos potenciales en árboles no excavados (controles) y realizamos 187 observaciones de estrategias de forrajeo de pájaros carpinteros. Los pájaros carpinteros seleccionaron sustratos nidos con duramen más blando que los sustratos potenciales no usados, independientemente de cualquier otra característica del árbol o parche de nidificación. La dureza de la madera alrededor de la cavidad nido incrementó con el tamaño corporal y la prevalencia de cincelado durante el forrajeo, rasgos positivamente correlacionados. A menudo, los pájaros carpinteros excavaron en árboles de Prosopis spp. (Algarrobos) pero raramente en Schinopsis balansae (Quebracho), árbol con madera interna excepcionalmente dura, en el cual aves adoptadoras frecuentemente nidifican en cavidades no excavadas. La dureza de la madera es fundamental para comprender el rol de los pájaros carpinteros como facilitadores de cavidades, entender los costos y beneficios de la excavación, e interpretar los patrones de excavación entre especies y entre distintos bosques del mundo.
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