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1. Movement ecology and sex are linked to barn owl microbial community composition

   https://doi.org/10.1111/mec.15398  

   Corl, Ammon; Charter, Motti; Rozman, Gabe; Toledo, Sivan; Turjeman, Sondra; Kamath, Pauline L.; Getz, Wayne M.; Nathan, Ran; Bowie, Rauri C. K. (April 2020, Molecular Ecology)

   Abstract The behavioural ecology of host species is likely to affect their microbial communities, because host sex, diet, physiology, and movement behaviour could all potentially influence their microbiota. We studied a wild population of barn owls (Tyto alba) and collected data on their microbiota, movement, diet, size, coloration, and reproduction. The composition of bacterial species differed by the sex of the host and female owls had more diverse bacterial communities than their male counterparts. The abundance of two families of bacteria, Actinomycetaceae and Lactobacillaceae, also varied between the sexes, potentially as a result of sex differences in hormones and immunological function, as has previously been found with Lactobacillaceae in the microbiota of mice. Male and female owls did not differ in the prey they brought to the nest, which suggests that dietary differences are unlikely to underlie the differences in their microbiota. The movement behaviour of the owls was associated with the host microbiota in both males and females because owls that moved further from their nest each day had more diverse bacterial communities than owls that stayed closer to their nests. This novel result suggests that the movement ecology of hosts can impact their microbiota, potentially on the basis of their differential encounters with new bacterial species as the hosts move and forage across the landscape. Overall, we found that many aspects of the microbial community are correlated with the behavioural ecology of the host and that data on the microbiota can aid in generating new hypotheses about host behaviour. 

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2. Evidence for a survival-driven traveling wave in a keystone boreal predator population

   https://doi.org/10.1073/pnas.2414052121  

   Arnold, Derek A; Breed, Greg A; Laufenberg, Jared S; Berg, Nathan D; Bertram, Mark R; Scotton, Bradley D; Kielland, Knut (October 2024, Proceedings of the National Academy of Sciences)

   Cyclical population dynamics are a common phenomenon in populations worldwide, yet the spatial organization of these cycles remains poorly understood. In this study, we investigated the spatial form and timing of a population collapse from 2018 to 2022 in Canada lynx (Lynx canadensis) across the northwest boreal forest. We analyzed survival, reproduction, and dispersal data from 143 individual global positioning system (GPS) collared lynx from populations across five study sites spanning interior Alaska to determine whether lynx displayed characteristics of a population wave following a concurrent wave in snowshoe hare (Lepus americanus) abundance. Reproductive rates declined across the study sites; however, site-level reproduction declined first in our easternmost study sites, supporting the idea of a population wave. Despite a clear increase in percent of dispersing lynx, there was no evidence of directional bias in dispersal following a hare population wave. Analysis did show increasingly poor survival for lynx dispersing to the east compared to combined resident and westward dispersal. This pattern is consistent with a survival-mediated population wave in lynx as the driver of the theorized population wave. The combination of these factors supports the idea of a hierarchical response to snowshoe hare population declines with a drop in lynx reproduction followed by increased dispersal, and finally reduced survival. All of this evidence is consistent with the expected characteristics of a population undergoing a traveling wave and supports the hypothesis that lynx presence may facilitate and mirror the underlying wave patterns in snowshoe hare. 

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3. Applications and Limitations of a Data Fusion Approach to Monitor Forest-Dwelling Wildlife

   King, Courtney L; Van_de_Kerk, Madelon; Breckheimer, Ian K; Vasquez, Matthew (June 2024, American Society of Mammologist)

   Ecologists have increasingly recognized opportunities to adapt and adopt methodologies and information originally intended for other purposes in a “data fusion” approach. Recently, there has been an influx of studies and training focused on using unmanned aerial vehicles (UAV’s) and remote sensing in wildlife research. Leveraging these technologies could supplement the often resource-intensive field approaches used to monitor population and habitat dynamics for forest dwelling species such as the snowshoe hare (Lepus americanus). Barriers remain, however, especially as agencies lacking the resources to collect data using UAV’s are restricted to freely available, not wildlife-specific, products. Furthermore, technologies may not be advanced enough to “see through” the canopy to the understory, relevant for species that rely on vegetation cover. We thereby conducted a case study to determine whether an approach outlined by previous authors could be successful, wherein the remote sensing products were accessible and originally collected for broader purposes. Our models did not adequately predict snowshoe hare fecal pellet numbers, pointing to deficiencies in the scale and type of available data derived from remote sensing. We also note potential shortcomings in non-invasive field techniques. Regardless, we maintain that open-access remotely sensed imagery is valuable when ground-truthed and combined with supplemental information, adding to knowledge within and beyond the fields of forestry and wildlife biology. 

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4. Aeroacoustics of Silent Owl Flight

   https://doi.org/10.1146/annurev-fluid-010518-040436  

   Jaworski, Justin W.; Peake, N. (January 2020, Annual Review of Fluid Mechanics)

   The ability of some species of owl to fly in effective silence is unique among birds and provides a distinct hunting advantage, but it remains a mystery as to exactly what aspects of the owl and its flight are responsible for this dramatic noise reduction. Crucially, this mystery extends to how the flow physics may be leveraged to generate noise-reduction strategies for wider technological application. We review current knowledge of aerodynamic noise from owls, ranging from live owl noise measurements to mathematical modeling and experiments focused on how owls may disrupt the standard routes of noise generation. Specialized adaptations and foraging strategies are not uniform across all owl species: Some species may not have need for silent flight, or their evolutionary adaptations may not be effective for useful noise reduction for certain species. This hypothesis is examined using mathematical models and borne out where possible by noise measurements and morphological observations of owl feathers and wings. 

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5. Introduction to the Symposium: Bio-Inspiration of Quiet Flight of Owls and Other Flying Animals: Recent Advances and Unanswered Questions

   https://doi.org/10.1093/icb/icaa128  

   Clark, Christopher J; Jaworski, Justin W (September 2020, Integrative and Comparative Biology)

   null (Ed.)

   Synopsis Animal wings produce an acoustic signature in flight. Many owls are able to suppress this noise to fly quietly relative to other birds. Instead of silent flight, certain birds have conversely evolved to produce extra sound with their wings for communication. The papers in this symposium synthesize ongoing research in “animal aeroacoustics”: the study of how animal flight produces an acoustic signature, its biological context, and possible bio-inspired engineering applications. Three papers present research on flycatchers and doves, highlighting work that continues to uncover new physical mechanisms by which bird wings can make communication sounds. Quiet flight evolves in the context of a predator–prey interaction, either to help predators such as owls hear its prey better, or to prevent the prey from hearing the approaching predator. Two papers present work on hearing in owls and insect prey. Additional papers focus on the sounds produced by wings during flight, and on the fluid mechanics of force production by flapping wings. For instance, there is evidence that birds such as nightbirds, hawks, or falcons may also have quiet flight. Bat flight appears to be quieter than bird flight, for reasons that are not fully explored. Several research avenues remain open, including the role of flapping versus gliding flight or the physical acoustic mechanisms by which flight sounds are reduced. The convergent interest of the biology and engineering communities on quiet owl flight comes at a time of nascent developments in the energy and transportation sectors, where noise and its perception are formidable obstacles. 

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