A Sonic Net deters European starlings Sturnus vulgaris from maize silage stores

Deterrents against avian pest species might be more effective if they were based on some aspect of the target species\u27 sensory salience. Sonic Nets broadcast a loud and spatiallyfocused pink noise that spans the frequency range of the target species\u27 vocalizations, restricting interspecific communication so that it is costly for birds to remain in the treated area. In parts of their native and introduced ranges, European starlings (Sturnus vulgaris) impact livestock operations where they consume and contaminate animal feed, damage infrastructure, and may contribute to pathogen transmission. We evaluated Sonic Net technology to exclude starlings from outdoor maize silage stores on 10 dairy farms in Cornwall, U.K. in February–March and November–December 2019. We quantified frequency of starling presence and approximate flock size and combined these to estimate starling burden in starling‐minutes before, during, and after Sonic Net treatment. During an initial proof‐of‐concept trial, each phase lasted 2 days, whilst in a second, longer experiment, treatment lasted 14 days. During Sonic Net treatment, frequency of starling presence was reduced, flock sizes were smaller, and starlingminutes were reduced by 94% and 89% in the 2‐day and 14‐day treatments, respectively. In the last 2 days of the 14‐day treatment, starling‐minutes remained 85% lower than before treatment, but 4 of 10 farms experienced some diminution of effects after 6 days. Sonic Nets had a significant and sustained effect, with potential for deterring avian pests from agricultural and other settings

A Primer of Conservation Behavior

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Eastern Bluebirds Alter their Song in Response to Anthropogenic Changes in the Acoustic Environment

Vocal responses to anthropogenic noise have been documented in several species of songbird. However, only a few studies have investigated whether these adjustments are made in real time or are longer-term responses to particular soundscapes. Furthermore, increased ambient noise often is accompanied by structural changes to the habitat, including the introduction of noisy roadways and the removal of native vegetation. To date, no studies have simultaneously investigated the impact of both acoustic and structural disturbance on the same species. The relevance of each of these variables must be quantified if we wish to refine our understanding of the ways in which human activities influence avian communication. In this study, we quantified both among-male and within-male adjustments of song in response to ambient noise, and also investigated whether anthropogenic modifications of the habitat explained variations in songs\u27 parameters. Recordings of songs were collected from male, breeding eastern bluebirds (Sialia sialis) residing in a network of nestboxes distributed across a gradient of anthropogenic disturbance. Levels of ambient noise were associated both with the average song-parameters of each male and with the change in a male\u27s song-parameters between the loudest and quietest periods at his nest box. Males\u27 song parameters were also related to habitat structure, as assessed using geographic information systems techniques. Males in noisier sites produced both higher-pitched and louder songs than did birds in quieter areas. Likewise, individual males demonstrated immediate adjustments to disturbance by noise, increasing the amplitude of their song between periods of quiet and loud ambient noise. Both spectral and temporal aspects of a male\u27s song were related to whether his habitat was more natural or anthropogenic. Our results indicate that males\u27 adjustments of song may represent simultaneous responses to multiple modifications of the habitat by humans. However, we also conclude that biotic noise remains an important influence on avian signals even in anthropogenic areas. We suggest that human habitats provide an ideal setting in which to perform experiments on communication strategies, with resulting data poised to reveal underlying evolutionary processes while also informing conservation and management

Experimental Exposure to Urban and Pink Noise Affects Brain Development and Song Learning in Zebra Finches (Taenopygia guttata)

Recently, numerous studies have observed changes in bird vocalizations—especially song—in urban habitats. These changes are often interpreted as adaptive, since they increase the active space of the signal in its environment. However, the proximate mechanisms driving cross-generational changes in song are still unknown. We performed a captive experiment to identify whether noise experienced during development affects song learning and the development of song-control brain regions. Zebra finches (Taeniopygia guttata) were bred while exposed, or not exposed, to recorded traffic urban noise (Study 1) or pink noise (Study 2). We recorded the songs of male offspring and compared these to fathers’ songs. We also measured baseline corticosterone and measured the size of song-control brain regions when the males reached adulthood (Study 1 only). While male zebra finches tended to copy syllables accurately from tutors regardless of noise environment, syntax (the ordering of syllables within songs) was incorrectly copied affected by juveniles exposed to noise. Noise did not affect baseline corticosterone, but did affect the size of brain regions associated with song learning: these regions were smaller in males that had been had been exposed to recorded traffic urban noise in early development. These findings provide a possible mechanism by which noise affects behaviour, leading to potential population differences between wild animals occupying noisier urban environments compared with those in quieter habitats

Asymmetry and Fighting Performance in the Shore Crab Carcinus maenas

Fluctuating asymmetries (left–right differences in symmetric traits) can be negatively related to fitness parameters in a number of biological systems. Hence, it has been suggested that symmetric individuals should outcompete asymmetric individuals during intraspecific agonistic encounters. However, there is a lack of experimental evidence for such a relationship. We investigated the relationship between trait asymmetry (both directional and fluctuating asymmetry) and the outcome of agonistic encounters among size-matched male shore crabs. Our findings indicate that cheliped (‘weapon claw’) directional asymmetry is not related to the outcome of fights, whereas fluctuating asymmetry in the fifth pereiopod, but not the second pereiopod, is negatively related to the likelihood of winning conspecific aggressive encounters. This relationship is most readily explained by a biomechanical advantage in symmetric individuals, as the fifth pereiopod is likely to be mechanically important in maintaining stability and balance during fighting. There is no evidence that asymmetry (in traits that display fluctuating asymmetry) is related to an intrinsic individual quality factor. None the less, the relative mechanical advantage of low asymmetry may give rise to fitness benefits in symmetric crabs that may have evolutionary consequences

Anthropogenic Noise is Associated with Reductions in the Productivity of Breeding Eastern Bluebirds (Sialia sialis)

Although previous studies have related variations in environmental noise levels with alterations in communication behaviors of birds, little work has investigated the potential long-term implications of living or breeding in noisy habitats. However, noise has the potential to reduce fitness, both directly (because it is a physiological stressor) and indirectly (by masking important vocalizations and/or leading to behavioral changes). Here, we quantified acoustic conditions in active breeding territories of male Eastern Bluebirds (Sialia sialis). Simultaneously, we measured four fitness indicators: cuckoldry rates, brood growth rate and condition, and number of fledglings produced (i.e., productivity). Increases in environmental noise tended to be associated with smaller brood sizes and were more strongly related to reductions in productivity. Although the mechanism responsible for these patterns is not yet clear, the breeding depression experienced by this otherwise disturbance-tolerant species indicates that anthropogenic noise may have damaging effects on individual fitness and, by extraction, the persistence of populations in noisy habitats. We suggest that managers might protect avian residents from potentially harmful noise by keeping acoustically dominant anthropogenic habitat features as far as possible from favored songbird breeding habitats, limiting noisy human activities, and/or altering habitat structure in order to minimize the propagation of noise pollution

Evaluating acoustic signals to reduce avian collision risk

Collisions with human-made structures are responsible for billions of bird deaths each year, resulting in ecological damage as well as regulatory and financial burdens to many industries. Acoustic signals can alert birds to obstacles in their flight paths in order to mitigate collisions, but these signals should be tailored to the sensory ecology of birds in flight as the effectiveness of various acoustic signals potentially depends on the influence of background noise and the relative ability of various sound types to propagate within a landscape. We measured changes in flight behaviors from zebra finches released into a flight corridor containing a physical obstacle, either in no-additional-sound control conditions or when exposed to one of four acoustic signals. We selected signals to test two frequency ranges (4 6 kHz or 6 8 kHz) and two temporal modulation patterns (broadband or frequency-modulated oscillating) to determine whether any particular combination of sound attributes elicited the strongest collision avoidance behaviors. We found that, relative to control flights, all sound treatments caused birds to maintain a greater distance from hazards and to adjust their flight trajectories before coming close to obstacles. There were no statistical differences among different sound treatments, but consistent trends within the data suggest that the 4 6 kHz frequency- modulated oscillating signal elicited the strongest avoidance behaviors. We conclude that a variety of acoustic signals can be effective as avian collision deterrents, at least in the context in which we tested these birds. These results may be most directly applicable in scenarios when birds are at risk of collisions with solid structures, such as wind turbines and communication towers, as opposed to window collisions or collisions involving artificial lighting. We recommend the incorporation of acoustic signals into multimodal collision deterrents and demonstrate the value of using behavioral data to assess collision risk