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1. 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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2. Tree diversity enhances predation by birds but not by arthropods across climate gradients

   https://doi.org/10.1111/ele.14427  

   Vázquez‐González, Carla; Castagneyrol, Bastien; Muiruri, Evalyne W; Barbaro, Luc; Abdala‐Roberts, Luis; Barsoum, Nadia; Fründ, Jochen; Glynn, Carolyn; Jactel, Hervé; McShea, William J; et al (May 2024, Ecology Letters)

   Abstract Tree diversity can promote both predator abundance and diversity. However, whether this translates into increased predation and top‐down control of herbivores across predator taxonomic groups and contrasting environmental conditions remains unresolved. We used a global network of tree diversity experiments (TreeDivNet) spread across three continents and three biomes to test the effects of tree species richness on predation across varying climatic conditions of temperature and precipitation. We recorded bird and arthropod predation attempts on plasticine caterpillars in monocultures and tree species mixtures. Both tree species richness and temperature increased predation by birds but not by arthropods. Furthermore, the effects of tree species richness on predation were consistent across the studied climatic gradient. Our findings provide evidence that tree diversity strengthens top‐down control of insect herbivores by birds, underscoring the need to implement conservation strategies that safeguard tree diversity to sustain ecosystem services provided by natural enemies in forests. 

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3. Beavers, Bugs and Chemistry: A Mammalian Herbivore Changes Chemistry Composition and Arthropod Communities in Foundation Tree Species

   https://doi.org/10.3390/f12070877  

   Durben, Rachel M.; Walker, Faith M.; Holeski, Liza; Keith, Arthur R.; Kovacs, Zsuzsi; Hurteau, Sarah R.; Lindroth, Richard L.; Shuster, Stephen M.; Whitham, Thomas G. (July 2021, Forests)

   null (Ed.)

   The North American beaver (Castor canadensis Kuhl) and cottonwoods (Populus spp.) are foundation species, the interactions of which define a much larger community and affect a threatened riparian habitat type. Few studies have tested the effect of these interactions on plant chemistry and a diverse arthropod community. We experimentally examined the impact of beaver foraging on riparian communities by first investigating beaver food preferences for one cottonwood species, Fremont cottonwood (P. fremontii S. Watson), compared to other locally available woody species. We next examined the impact of beaver foraging on twig chemistry and arthropod communities in paired samples of felled and unfelled cottonwood species in northern Arizona (P. fremontii) and southwestern Colorado (narrowleaf cottonwood, P. angustifolia James, and Eastern cottonwood, P. deltoides W. Bartram ex Marshall). Four major patterns emerged: (1) In a cafeteria experiment, beavers chose P. fremontii six times more often than other woody native and exotic species. (2) With two cottonwood species, we found that the nitrogen and salicortin concentrations were up to 45% greater and lignin concentration 14% lower in the juvenile resprout growth of felled trees than the juvenile growth on unfelled trees (six of seven analyses were significant for P. fremontii and four of six were significant for P. angustifolia). (3) With two cottonwood species, arthropod community composition on juvenile branches differed significantly between felled and unfelled trees, with up to 38% greater species richness, 114% greater relative abundance and 1282% greater species diversity on felled trees (six of seven analyses with P. fremontii and four of six analyses with P. angustifolia were significant). The above findings indicate that the highest arthropod diversity is achieved in the heterogenous stands of mixed felled and unfelled trees than in stands of cottonwoods, where beavers are not present. These results also indicate that beaver herbivory changes the chemical composition in 10 out of 13 chemical traits in the juvenile growth of two of the three cottonwood species to potentially allow better defense against future beaver herbivory. (4) With P. deltoides, only one of five analyses in chemistry was significant, and none of the four arthropod community analyses were significant, suggesting that this species and its arthropod community responds differently to beaver. Potential reasons for these differences are unknown. Overall, our findings suggest that in addition to their impact on riparian vegetation, other mammals, birds, and aquatic organisms, beavers also may define the arthropod communities of two of three foundation tree species in these riparian ecosystems. 

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4. Partial shading by solar panels delays bloom, increases floral abundance during the late-season for pollinators in a dryland, agrivoltaic ecosystem

   https://doi.org/10.1038/s41598-021-86756-4  

   Graham, Maggie; Ates, Serkan; Melathopoulos, Andony P.; Moldenke, Andrew R.; DeBano, Sandra J.; Best, Lincoln R.; Higgins, Chad W. (December 2021, Scientific Reports)

   null (Ed.)

   Abstract Habitat for pollinators is declining worldwide, threatening the health of both wild and agricultural ecosystems. Photovoltaic solar energy installation is booming, frequently near agricultural lands, where the land underneath ground-mounted photovoltaic panels is traditionally unused. Some solar developers and agriculturalists in the United States are filling the solar understory with habitat for pollinating insects in efforts to maximize land-use efficiency in agricultural lands. However, the impact of the solar panel canopy on the understory pollinator-plant community is unknown. Here we investigated the effects of solar arrays on plant composition, bloom timing and foraging behavior of pollinators from June to September (after peak bloom) in full shade plots and partial shade plots under solar panels as well as in full sun plots (controls) outside of the solar panels. We found that floral abundance increased and bloom timing was delayed in the partial shade plots, which has the potential to benefit late-season foragers in water-limited ecosystems. Pollinator abundance, diversity, and richness were similar in full sun and partial shade plots, both greater than in full shade. Pollinator-flower visitation rates did not differ among treatments at this scale. This demonstrates that pollinators will use habitat under solar arrays, despite variations in community structure across shade gradients. We anticipate that these findings will inform local farmers and solar developers who manage solar understories, as well as agriculture and pollinator health advocates as they seek land for pollinator habitat restoration in target areas. 

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5. Bird abundance and its environmental controls in major ecosystems across the U.S.

   Qian, Anita; Xu, Xiaofeng (August 2024, ESA)

   Qian, Anita; Xu, Xiaofeng (Ed.)

   Birds play a crucial role in maintaining the balance and health of ecosystems worldwide, with their significance extending from ecological functions to cultural symbolism. Ecologically, birds contribute to pest control by preying on insects, regulating populations, and mitigating agricultural damage. They also aid in seed dispersal and pollination, facilitating vegetation growth and plant reproduction. Furthermore, birds serve as environmental indicators, reflecting broader ecological shifts. Recently, the National Ecological Observation Network (NEON) has undertaken the task of monitoring bird populations across various U.S. ecosystems. The project aims to decipher bird abundance patterns during peak growing seasons, synthesizing data on variables such as bird counts, beetle populations, latitude, longitude, tree dimensions, and vegetation productivity during 2017-2022 sourced from NEON databases. The findings reveal that bird counts decrease from low to high latitudes, with both beetles and vegetation productivity positively influencing bird abundance, while tree breast height diameter shows weak correlation. Strong inter-annual variations in bird counts were observed nationwide. Both correlation analysis and structural equation modeling underscore vegetation's pivotal role in bird abundance. In essence, the developed bird count data system offers valuable insights into bird and ecosystem health, aiding communities in understanding and preserving these vital ecosystems. 

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