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1. Data and code from "Black-throated blue warblers (Setophaga caerulescens) exhibit diet flexibility and track seasonal changes in insect availability" Kaiser et al. 2024 Ecology and Evolution

   https://doi.org/10.6073/pasta/2091305bf6653a8aaa26964cf1470740  

   Kaiser, Sara A; Forg, Lindsey; Stillman, Andrew; Deitsch, John F; Sillett, Scott; Clucas, Gemma (January 2024, Environmental Data Initiative)

   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 two-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. These data were gathered as part of the Hubbard Brook Ecosystem Study (HBES). The HBES is a collaborative effort at the Hubbard Brook Experimental Forest, which is operated and maintained by the US Forest Service, Northern Research Station. 

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2. Fecal metabarcoding reveals differences in nestling diet across years with extreme variation in climate and arthropod availability in a montane songbird

   https://doi.org/10.1093/ornithology/ukag012  

   Whitenack, Lauren E; Sonnenberg, Benjamin R; Branch, Carrie L; Welklin, Joseph F; Clucas, Gemma V; Pravosudov, Vladimir V (March 2026, Ornithology)

   Abstract 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. 

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3. Syntopic diet divergence inferred from metabarcoding in a pair of parulid warblers: Setophaga virens (Black-throated Green Warbler) and Seiurus aurocapilla (Ovenbird)

   https://doi.org/10.1093/ornithology/ukaf059  

   Toews, David_P L; Baiz, Marcella D; Benavides_C, Andrea; Deans, Andrew R; Phung, Lan-Nhi; Szarmach, Stephanie J; Wood, Andrew W (October 2025, Ornithology)

   Abstract The role of diet in driving ecological differences across the radiation of parulid wood warblers has been a topic of substantial debate. The inferences made in Robert MacArthur’s original study of their niche differences relied heavily on observations from microhabitat partitioning. How these different foraging behaviors translated to distinct diets and, more specifically, individual prey items has been less clear. Here, we use fecal metabarcoding of 2 syntopic insectivorous warblers—Setophaga virens (black-throated Green Warbler) and Seiurus aurocapilla (Ovenbird)—to complement and expand previous work, and we address past limitations by densely sampling many birds at the same location over a short period of time. We found highly significant differences in diet composition using several multivariate measures of diversity. In an analysis of individual diet proportions of insect orders, S. aurocapilla consumed more beetles and flies (Coleoptera and Diptera), whereas S. virens consumed more “true bugs” (Hemiptera) and stoneflies (Plecoptera). At the arthropod species level, we found that both warblers readily consumed invasive spongy moths (Lymantria dispar), and we identified 9 other arthropod species that significantly differed between the warblers. Of those, for 3 spider taxa, we combined warbler diet information with observations from arthropod collections and showed that spiders, which were more likely to be encountered on the ground, were exclusively eaten by S. aurocapilla whereas those encountered in the canopy were more likely to be consumed by S. virens, fitting with the expected vertical foraging stratification of the warblers. We interpret these diet differences as likely due to these 2 warbler species “opportunistically” encountering different arthropod assemblages in distinct foraging strata as opposed to “preferentially” consuming different prey. Our research emphasizes the benefits of extending analyses to more distantly related taxa—beyond those considered by MacArthur—and suggests a need for similar fine-scale studies within genera to enhance our understanding of dietary dynamics. 

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4. Consequences of arthropod community structure for an at-risk insectivorous bird

   https://doi.org/10.1371/journal.pone.0281081  

   Nell, Cee S; Pratt, Riley; Burger, Jutta; Preston, Kristine L; Treseder, Kathleen K; Kamada, Dana; Moore, Karly; Mooney, Kailen A (February 2023, PLOS ONE)

   Yue, Bi-Song (Ed.)

   Global declines in bird and arthropod abundance highlights the importance of understanding the role of food limitation and arthropod community composition for the performance of insectivorous birds. In this study, we link data on nestling diet, arthropod availability and nesting performance for the Coastal Cactus Wren (Campylorhynchus brunneicapillus sandiegensis), an at-risk insectivorous bird native to coastal southern California and Baja Mexico. We used DNA metabarcoding to characterize nestling diets and monitored 8 bird territories over two years to assess the relationship between arthropod and vegetation community composition and bird reproductive success. We document a discordance between consumed prey and arthropod biomass within nesting territories, in which Diptera and Lepidoptera were the most frequently consumed prey taxa but were relatively rare in the environment. In contrast other Orders (e.g., Hemiptera, Hymenoptera)were abundant in the environment but were absent from nestling diets. Accordingly, variation in bird reproductive success among territories was positively related to the relative abundance of Lepidoptera (but not Diptera), which were most abundant on 2 shrub species (Eriogonum fasciculatum,Sambucus nigra)of the 9 habitat elements characterized (8 dominant plant species and bare ground). Bird reproductive success was in turn negatively related to two invasive arthropods whose abundance was not associated with preferred bird prey, but instead possibly acted through harassment (Linepithema humile; Argentine ants) and parasite transmission or low nutritional quality (Armadillidium vulgare; pill-bug). These results demonstrate how multiple aspects of arthropod community structure can influence bird performance through complementary mechanisms, and the importance of managing for arthropods in bird conservation efforts. 

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5. Seasonal Effects on the Fecal Microbial Composition of Wild Greater Thick-Tailed Galagos (Otolemur crassicaudatus)

   https://doi.org/10.1007/s10764-023-00407-1  

   Long, Channen; Scheun, Juan; Sauther, Michelle Linda; Cuozzo, Frank P.; Millette, James; Tordiffe, Adrian Stephen (November 2023, International Journal of Primatology)

   Setchell, J (Ed.)

   Abstract Bacterial communities present in the host digestive tract are important for the breakdown and absorption of nutrients required by the host. Changes in diet and the environment are major factors affecting the composition and diversity of the fecal microbiome. In addition to changes in ambient temperature and rainfall, primates living in seasonal temperate environments also need to adapt to seasonal changes in food resource quantity and quality. However, there is a lack of information about the fecal microbiome in African strepsirrhines relative to other primate taxa. We examined the effects of seasonal dietary and environmental changes on fecal microbial alpha diversity and composition in wild greater thick-tailed galagos (Otolemur crassicaudatus) at Lajuma Research Centre, South Africa. We collected fecal samples and assessed food availability and weather in summer and winter across 1 year and used 16S rRNA next-generation sequencing to characterise the fecal microbiome of 49 animals. We found significant increases in rainfall, ambient temperature, and food availability in summer compared with winter. However, we found no significant changes in body mass or in the overall diversity of bacterial species present in fecal samples between the two seasons. We found significant decreases in the abundance of certain bacterial families in winter, suggesting a change in diet. Our findings suggest that greater thick-tailed galagos can find food resources to maintain their body mass throughout the year. Our insights into the seasonal fecal microbiome of greater thick-tailed galagos add to the growing knowledge and understanding of fecal microbiomes in primates and how they help primates cope with changes to their environments. 

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