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The Yellow Warbler (Setophaga petechia) is a Neotropical migratory passerine that breeds in riparian and other wetland habitats across North America. Yellow Warblers use several woody plants as substrates to build nests on, including both native and invasive species. We monitored Yellow Warbler nests from 2018 to 2021 in east-central Illinois, USA, and observed similar numbers of nests in invasive and native plant substrates. We also documented qualitatively lower nest mortality for nests placed in invasive plants compared to native plants. The patterns documented here could suggest that for Yellow Warblers, invasive plant encroachment in riparian habitat may not have strong negative repercussions on their reproductive success. Received 26 April 2023. Accepted 26 December 2023. Key words: invasive species, nest substrate, nest survival. La reinita amarilla (Setophaga petechia) es un paserino migratorio neotropical que se reproduce en habitats riparios y en otros humedales en Norteamerica. Las reinitas amarillas usan varias plantas lenosas como sustrato sobre los cuales con-struir sus nidos, incluyendo tanto especies nativas como invasoras. Monitoreamos nidos de reinita amarilla del 2018 al 2021 en la region centro-este de Illinois, Estados Unidos, y observamos numeros similares de nidos en sustratos de plantas nativas y no nativas. Tambien documentamos una mortalidad de nidos cualitati-vamente menor para nidos colocados sobre plantas invasoras que sobre plantas nativas. Los patrones documentados aqui podrian sugerir que para la reinita amarilla, la llegada de plantas invasoras en habitats riparios podria no tener fuertes repercusiones negativas en su exito reproductivo. Palabras clave: especies invasivas, sustrato del nido. sobrevivencia del nido., The Yellow Warbler (Setophaga petechia) is a Neotropical migratory passerine that breeds in riparian and other wetland-edge habitats across North America and uses several woody plant substrates for nest building [...]

Avian eggshell pigmentation may provide information about a female's physiological condition, in particular her state of oxidative balance. Previously we found that female House Wrens (Troglodytes aedon Vieillot, 1809) with lighter, less-maculated, and redder ground-colored shells were older and produced heavier offspring than females laying more-maculated and browner eggs. The strong pro-oxidant protoporphyrin is responsible for this species' eggshell pigmentation, so differences in pigmentary coloration may be related to eggshell protoporphyrin content and reflect female oxidative balance and condition during egg formation. Therefore, we tested the assumption that egg-surface coloration is related to the amount of protoporphyrin in the shell matrix. We analyzed digital photographs of eggs to determine maculation coverage as a measure of the overall ground coloration of the egg and its red-, green-, and blue-channel pixel values. Pigments were then extracted from these same eggs and analyzed using high-performance liquid chromatography. There was a strong, positive relationship between eggshell redness and protoporphyrin content of eggshells, but no relationship between percent maculation and protoporphyrin content. Thus, when older, larger females deposit more protoporphyrin in their eggshells, this may reflect a tolerance for high levels of circulating protoporphyrin or an effective mechanism for off-loading protoporphyrin into the eggshell matrix. Key words: House Wren, Troglodytes aedon, eggs, female quality, HPLC, eggshell pigmentation. La pigmentation des coquilles d'oeuf d'oiseaux pourrait fournir de l'information sur l'état physiologique des femelles, notamment sur leur équilibre oxydatif. Nous avons déjà relevé que des troglodytes familiers (Troglodytes aedon Vieillot, 1809) femelles dont les coquilles d'oeus sont plus claires, moins maculées et de couleur de base plus rouge sont plus âgées et produisent des rejetons plus lourds que les femelles qui pondent des oeufs plus maculés et bruns. Comme la protoporphyrine, un puissant pro-oxydant, est responsable de la pigmentation de la coquille des oeufs de cette espèce, des différences de coloration pigmentaire pourraient être reliées à la teneur en protoporphyrine de la coquille et refléter l'équilibre oxydatif et l'état physiologique des femelles durant la formation des oeufs. Nous avons donc vérifié l'hypothèse selon laquelle la coloration de la surface des oeufs est reliée à la quantité de protoporphyrine dans la matrice de la coquille. Nous avons analysé des photographies numériques d'oeufs pour déterminer la couverture de tâches (maculation) comme mesure de la coloration de base globale de l'oeuf, et les valeurs des pixels des canaux rouges, verts et bleus. Des pigments ont ensuite été extraits de ces mêmes oeufs et analysés par chromatographie liquide à haute performance. Une forte relation positive est relevée entre l'intensité de la couleur rouge et la teneur en protoporphyrine des coquilles d'oeufs, alors qu'aucune relation n'est notée entre le pourcentage de tâches et la teneur en protoporphyrine. Ainsi, le dépôt par des femelles plus âgées et plus grandes de plus importantes quantités de protoporphyrine dans les coquilles de leurs oeufs pourrait refléter une tolérance à des concentrations élevées de protoporphyrine en circulation ou un mécanisme efficace de délestage de protoporphyrine vers la matrice des oeufs. [Traduit par la Rédaction] Mots-clés : troglodyte familier, Troglodytes aedon, oeufs, qualité des femelles, CLHP, pigmentation des coquilles d'oeuf., Introduction Eggshell pigmentation is an extended phenotypic trait of female birds, one that may provide information about a female's underlying physiological condition (Moreno and Osorno 2003; Moreno et al. 2006; [...]

Alarm signals have evolved to communicate imminent threats to conspecifics but animals may also perceive other species' alarm displays to obtain adaptive information. In birds, mixed‐species foraging flocks are often structured around a focal sentinel species, which produces reliable alarm calls that inform eavesdropping non‐sentinel heterospecifics about predation risk. Ongoing work has revealed that several species can recognize the alarm calls of certain sentinel species even without prior encounters, including when these are from distant biogeographic regions. Similar work has yet to examine whether naive subjects' responses to unfamiliar sentinel alarm calls differ from responses to non‐sentinel alarm calls. Here we played the alarm calls of three subtropical Asian bird species that participate in mixed species flocks, to temperate North American birds. Birds responded most to the alarm call of an allopatric core sentinel and a local sympatric sentinel control species, less so to an allopatric non‐core sentinel, and least so to an allopatric non‐sentinel and a negative control stimulus. These patterns provide evidence that broad phylogenetic and geographic recognition is a pertinent aspect of sentinel alarm calls in general. [ABSTRACT FROM AUTHOR]

Introduced species can represent quasi-experimental, anthropogenic case studies of both ecological and evolutionary principles. When these species are firmly established, competitive interactions between native and introduced species, including foraging, spacing, and breeding competition, may be among the ecological costs incurred from such species invasions. In turn, genetic and/or plasticity-driven changes in behavior and morphology could also take place in the invading species with increasing introduction lag (time since the onset of introduction). Critically, however, introduction lag is difficult to study in any single non-native population without long-term observations, and, instead, it requires geographically repeated measures of the focal response variables across invasive populations that were introduced at different times. Here we tested a priori predictors of predator-avoidance behaviors through the flight initiation distance (FID) assay of a widely distributed invasive bird species, the common myna Acridotheres tristis. The species was extensively and consistently sampled throughout most of its independently introduced ranges across all hemispheres. Critically, FID increased with greater introduction lag. We also detected additional functional patterns in that FID increased towards the rural range within a continuous metric of urban-rural gradient and also at shorter distances from the Equator. Any robust study of FID must also include proximate predictors as well and, accordingly, we found that FID increased with greater starting distance, with lower immediate human density, with flighted over walking escape responses, and at lower heights of a bird's perch above ground but was unrelated to myna group size. Respectively, these factors are informative about the sensory cues triggering anti-predator behaviors in invasive mynas and imply an adaptive set of patterns of anti-predator responses in the introduced ranges of this species. Control measures of invasive common myna populations should take into account their extensive behavioral and cognitive flexibilities and adjust the planned management methods accordingly. [ABSTRACT FROM AUTHOR]

The role of species interactions, as well as genetic and environmental factors, all likely contribute to the composition and structure of the gut microbiome; however, disentangling these independent factors under field conditions represents a challenge for a functional understanding of gut microbial ecology. Avian brood parasites provide unique opportunities to investigate these questions, as brood parasitism results in parasite and host nestlings being raised in the same nest, by the same parents. Here we utilized obligate brood parasite brown‐headed cowbird nestlings (BHCO; Molothrus ater) raised by several different host passerine species to better understand, via 16S rRNA sequencing, the microbial ecology of brood parasitism. First, we compared faecal microbial communities of prothonotary warbler nestlings (PROW; Protonotaria citrea) that were either parasitized or non‐parasitized by BHCO and communities among BHCO nestlings from PROW nests. We found that parasitism by BHCO significantly altered both the community membership and community structure of the PROW nestling microbiota, perhaps due to the stressful nest environment generated by brood parasitism. In a second dataset, we compared faecal microbiotas from BHCO nestlings raised by six different host passerine species. Here, we found that the microbiota of BHCO nestlings was significantly influenced by the parental host species and the presence of an inter‐specific nestmate. Thus, early rearing environment is important in determining the microbiota of brood parasite nestlings and their companion nestlings. Future work may aim to understand the functional effects of this microbiota variability on nestling performance and fitness. [ABSTRACT FROM AUTHOR]