Sara Ann Kaiser

The post‐fledging period – the time between a juvenile bird leaving its nest and dispersing or migrating from its natal site – is a critical yet challenging aspect of avian ecology to study. Past reviews have advanced our knowledge of the post‐fledging period by focusing on a particular topic or taxon but have yet to describe patterns of survival and behaviour across the entire post‐fledging literature. Here we review research on the post‐fledging ecology of birds across taxa to ( i ) synthesize emergent patterns, ( ii ) highlight critical knowledge gaps, and ( iii ) identify promising future frontiers in research. Our review revealed a general dichotomy in the post‐fledging literature, with studies on altricial and precocial birds using different terminology and rarely citing one another. Consequently, we compared the post‐fledging ecology of altricial and precocial birds while synthesizing patterns and knowledge gaps in the literature. We showed that altricial and precocial birds share many similarities in their post‐fledging behaviour, movement, habitat use, parental care, and survival, despite key differences in their ontogenies (e.g. development in the egg and nestling period length). In particular, altricial and precocial birds showed similar trends in fledgling survival with age (positive association), exhibit similarities in selecting post‐fledging habitat (often selecting for denser, more complex vegetation that provides cover), and in movement strategies (moving less at younger age to avoid predator detection). Differences were also apparent, with altricial and precocial birds differing in key traits that carry over from the nesting stage to influence fledgling survival (e.g. mass versus wing development). Nevertheless, differences in descriptions of the post‐fledging period have, in part, resulted in studies on altricial and precocial birds being disconnected in the literature, highlighting a need for a unifying, standardized terminology for the period after birds leave the nest. Comparative studies and meta‐analyses across the altricial–precocial spectrum are also needed to bridge the two worlds. The post‐fledging field has grown steadily over the past few decades, but this life‐history stage remains understudied for nearly 90% of avian taxa and important frontiers remain largely unexplored: understudied geographical regions and taxa, brood parasites, ecophysiology, impacts of urbanization and climate‐induced environmental change, and impacts of technology used to study this period. Our review emphasizes the importance of the post‐fledging period for avian population dynamics and life histories, and highlights the great potential of research into this key developmental stage to advance our understanding of the ecology, evolution, and conservation of birds.

Changes in leaf phenology from warming spring and autumn temperatures have lengthened the temperate zone growing “green” season and breeding window for migratory birds in North America. However, the fitness benefits of an extended breeding season will depend, in part, on whether species have sufficient dietary flexibility to accommodate seasonal changes in prey availability. We used fecal DNA metabarcoding to test the hypothesis that seasonal changes in the diets of the insectivorous, migratory black‐throated blue warbler ( Setophaga caerulescens ) track changes in the availability of arthropod prey at the Hubbard Brook Experimental Forest, New Hampshire, USA. We examined changes across the breeding season and along an elevation gradient encompassing a 2‐week difference in green season length. From 98 fecal samples, we identified 395 taxa from 17 arthropod orders; 242 were identified to species, with Cecrita guttivitta (saddled prominent moth), Theridion frondeum (eastern long‐legged cobweaver), and Philodromus rufus (white‐striped running crab spider) occurring at the highest frequency. We found significant differences in diet composition between survey periods and weak differences among elevation zones. Variance in diet composition was highest late in the season, and diet richness and diversity were highest early in the season. Diet composition was associated with changes in prey availability surveyed over the green season. However, several taxa occurred in diets more or less than expected relative to their frequency of occurrence from survey data, suggesting that prey selection or avoidance sometimes accompanies opportunistic foraging. This study demonstrates that black‐throated blue warblers exhibit diet flexibility and track seasonal changes in prey availability, which has implications for migratory bird responses to climate‐induced changes in insect communities with longer green seasons.

La incubación de un nido vacío es un fenómeno poco detectado en aves pero ha sido documentado en diversas especies. Las causas de esta anomalía reproductiva no son claras pero se han dado reportes previos en regiones con alta contaminación aérea. Proporcionamos un reporte detallado de una hembra de reinita Setophaga caerulescens incubando un nido vacío por 8 días en Hubbard Brook Experimental Forest, New Hampshire, Estados Unidos, de mayo a junio 2023 y exploramos posibles explicaciones basadas en una revisión de literatura de reproducción anómala. Nuestra observación coincide con la presencia de humo de extensos incendios forestales en Quebec, Canadá. Los incendios fueron causados por temperaturas récord y condiciones de sequía. El humo de los incendios forestales incrementó la contaminación por partículas en el aire. Encontramos 231 reportes publicados de 11 especies de aves incubando nidos vacíos. Las especies que anidaban en cavidades en Europa comprendían el 45% de las especies (5 de 11) y 96% de los reportes (225 de 231). Aunque muchos reportes no incluían una explicación clara, las hipótesis más comunes que explicaban la incubación de nidos vacíos incluían los siguientes factores la exposición a contaminación ambiental (81% de los reportes, 167 de 206), deficiencia de calcio por acidificación ambiental (19% de reportes, 40 de 206) y enfermedad y/o infertilidad (4% de los casos, 8 de 206). Nuestra síntesis de las observaciones publicadas resalta la necesidad de más datos de individuos expresando este comportamiento inusual. Estos datos mejorarían nuestra comprensión de cómo la puesta de huevos y el éxito reprodcutivo responden a factores intrínsecos y ambientales, incluyendo emisiones de incendios forestales, que se pronostican en aumento con el cambio climático. Palabras clave: calidad de aire, comportamiento anormal, contaminación del aire, fracaso reproductivo, humo de incendio forestal, incubación de nido vacío.

Scott Lanyon The American Ornithological Society (AOS) offers two service awards, the Peter R. Stettenheim Service Award and the Marion Jenkinson Service Award, to recognize AOS members who have provided continued, exceptional service to ­ornithology and to the Society. This year, Scott Lanyon is awarded the Peter R. Stettenheim Service Award. Scott Lanyon is the Vice Provost and Dean of Graduate Education at the University of Minnesota, Minneapolis, MN, USA. Dr. Lanyon has a long history of sustained leadership in the American Ornithologists’ Union (AOU) as well as today in the AOS. He has provided exceptional leadership on numerous committees and on the AOS Council for more than 20 years. Notably, Dr. Lanyon served as AOU president during the merger with the Cooper Ornithological Society to form the AOS. In that role he worked to unify disparate views and established a transparent and ­collaborative tone within leadership, which served as a foundation for developing inclusivity within the society and relevancy to all ornithologists. Dr. Lanyon also played a pivotal leadership role in launching the AOS’s strategic planning efforts, helping to clarify and give direction to the society’s role in the broader world of professional and amateur ornithology. Today, he continues to be involved in strategic planning for the society, helping it move forward to meet the unique challenges and opportunities for ornithology in the 21st century. Dr. Lanyon has been a thoughtful and generous mentor for many early-career ornithologists, working to ensure that all feel welcome in the society. Dr. Lanyon was elected as an AOS Elective Member in 1986 and an AOS Fellow in 1992.

James River The American Ornithological Society (AOS) offers two service awards, the Peter R. Stettenheim Service Award and the Marion Jenkinson Service Award, to recognize AOS members who have provided continued, exceptional service to ornithology and to the Society. This year, James Rivers is awarded the Marion Jenkinson Service Award. James Rivers is an Assistant Professor of Wildlife Ecology, Forest Engineering, Resources & Management, at Oregon State University, Portland. Dr. Rivers has served on numerous AOS committees, starting when he was a graduate student. Most notable is Dr. Rivers’ leadership in student affairs, including serving as chair of the Student Affairs Committee shortly after its establishment. His leadership of this ­committee led to improved services for students and early professionals, ensuring more impactful meetings (including initiating the very popular Quiz Bowl at the annual meetings), and expanding professional development. Dr. Rivers continued these efforts for several years as an active ­member of the Early Professionals Committee as well as while ­serving as an AOS Elective Councilor. In addition to being an enduring advocate for students and early professionals in the society, Dr. Rivers has contributed directly to several AOS conferences, has helped develop new awards to recognize significant contributions, and continues to serve as an associate editor for Ornithology. Dr. Rivers also received the 2012 Ned K. Johnson Early Investigator Award and was elected as an AOS Elective Member in 2007 and an AOS Fellow in 2015.

Artificial light at night (ALAN) is a globally widespread and expanding form of anthropogenic change that impacts arthropod biodiversity. ALAN alters interspecific interactions between arthropods, including predation and parasitism. Despite their ecological importance as prey and hosts, the impact of ALAN on larval arthropod stages, such as caterpillars, is poorly understood. We examined the hypothesis that ALAN increases top-down pressure on caterpillars from arthropod predators and parasitoids. We experimentally illuminated study plots with moderate levels (10–15 lux) of LED lighting at light-naive Hubbard Brook Experimental Forest, New Hampshire. We measured and compared between experimental and control plots: (i) predation on clay caterpillars, and (ii) abundance of arthropod predators and parasitoids. We found that predation rates on clay caterpillars and abundance of arthropod predators and parasitoids were significantly higher on ALAN treatment plots relative to control plots. These results suggest that moderate levels of ALAN increase top-down pressure on caterpillars. We did not test mechanisms, but sampling data indicates that increased abundance of predators near lights may play a role. This study highlights the importance of examining the effects of ALAN on both adult and larval life stages and suggests potential consequences of ALAN on arthropod populations and communities.

Understanding the demographic drivers of range contractions is important for predicting species' responses to climate change; however, few studies have examined the effects of climate change on survival and recruitment across species' ranges. We show that climate change can drive trailing edge range contractions through the effects on apparent survival, and potentially recruitment, in a migratory songbird. We assessed the demographic drivers of trailing edge range contractions using a long‐term demography dataset for the black‐throated blue warbler (Setophaga caerulescens) collected across elevational climate gradients at the trailing edge and core of the breeding range. We used a Bayesian hierarchical model to estimate the effect of climate change on apparent survival and recruitment and to forecast population viability at study plots through 2040. The trailing edge population at the low‐elevation plot became locally extinct by 2017. The local population at the mid‐elevation plot at the trailing edge gradually declined and is predicted to become extirpated by 2040. Population declines were associated with warming temperatures at the mid‐elevation plot, although results were more equivocal at the low‐elevation plot where we had fewer years of data. Population density was stable or increasing at the range core, although warming temperatures are predicted to cause population declines by 2040 at the low‐elevation plot. This result suggests that even populations within the geographic core of the range are vulnerable to climate change. The demographic drivers of local population declines varied between study plots, but warming temperatures were frequently associated with declining rates of population growth and apparent survival. Declining apparent survival in our study system is likely to be associated with increased adult emigration away from poor‐quality habitats. Our results suggest that demographic responses to warming temperatures are complex and dependent on local conditions and geographic range position, but spatial variation in population declines is consistent with the climate‐mediated range shift hypothesis. Local populations of black‐throated blue warblers near the warm‐edge range boundary at low latitudes and low elevations are likely to be the most vulnerable to climate change, potentially leading to local extirpation and range contractions.

Sexual selection studies widely estimate several metrics, but values may be inaccurate because standard field methods for studying wild populations produce limited data (e.g., incomplete sampling, inability to observe copulations directly). We compared four selection metrics (Bateman gradient, opportunity for sexual selection, opportunity for selection, and s(max)') estimated with simulated complete and simulated limited data for 15 socially monogamous songbird species with extra-pair paternity (4-54% extra-pair off-spring). Inferring copulation success from offspring parentage creates non-independence between these variables and systematically underestimates copulation success. We found that this introduces substantial bias for the Bateman gradient, opportunity for sexual selection, and s'(max). Notably, 47.5% of detected Bateman gradients were significantly positive for females, suggesting selection on females to copulate with multiple males, though the true Bateman gradient was zero. Bias generally increased with the extent of other sources of data limitations tested (nest predation, male infertility, and unsampled floater males). Incomplete offspring sampling introduced bias for all metrics except the Bateman gradient, while incomplete sampling of extra-pair sires did not introduce additional bias when sires were a random subset of breeding males. Overall, our findings demonstrate how biases due to field data limitations can strongly impact the study of sexual selection.