Using conspecific broadcast for Willow Flycatcher restoration

Abstract

ABSTRACT. Willow Flycatcher (Empidonax traillii) populations have been in decline across the western United States for decades. California populations are especially vulnerable with fewer than 500 pairs remaining in the state. Declines and local extirpations continue despite extensive habitat restoration and improved management designed to help conserve Willow Flycatchers. Such efforts may have failed to help reverse these trends in part because Willow Flycatchers rarely recolonize habitat after extirpation, regardless of present habitat suitability. Failure to recolonize habitat may be because prospecting Willow Flycatchers, like many other songbird species, assess habitat suitability based on the presence of conspecifics, making them unlikely to consider unoccupied habitat as potential breeding grounds. If true, broadcasting conspecific vocalizations in suitable but unoccupied habitat could help facilitate recolonization. During the 2016 and 2017 breeding seasons, we assessed the effectiveness of providing artificial social cues as a means of restoring Willow Flycatchers to suitable but unoccupied restored meadows in the Sierra Nevada mountains of California. We selected 14 experimental meadows where conspecific songs were broadcast during the settlement and breeding periods and 19 control meadows where no broadcasts took place. All the meadows were recently restored, contain high-quality habitat with hydrological characteristics and vegetation similar to meadows where Sierra Willow Flycatchers successfully breed, and were confirmed to be unoccupied in the year prior to their inclusion in the study. We observed Willow Flycatchers at five of 14 experimental meadows (35.75%) during the breeding season and at one of 19 control meadows (5.3%). We found that habitat characteristics also play a role in the efficacy of this technique, as Willow Flycatcher presence was highly significantly related to the combination of both the experimental treatment and meadow size. These results demonstrate that within large, restored meadows, conspecific broadcasts may be an effective strategy for restoring Willow Flycatchers. Utilisation de la diffusion de chants de conspécifiques pour le rétablissement du Moucherolle des saulesRÉSUMÉ. Les populations de Moucherolles des saules (Empidonax traillii) sont à la baisse dans tout l'ouest des États-Unis depuis des décennies. Les populations californiennes sont particulièrement vulnérables, comptant moins de 500 couples. Les baisses et les disparitions locales se produisent toujours malgré les efforts importants de restauration d'habitat et d'aménagement ciblant la conservation de ces moucherolles. Ces efforts pourraient avoir failli à renverser les tendances, en partie en raison du fait que le Moucherolle des saules recolonise rarement un habitat qu'il a abandonné, sans égard aux conditions actuelles propices. L'échec de la recolonisation d'habitat est peut-être attribuable au fait que les moucherolles qui prospectent, tout comme de nombreuses autres espèces d'oiseaux chanteurs, évaluen...

Bird response to hydrologic restoration of montane riparian meadows

“…We also assumed no larger‐scale population trends contributed to the time‐since‐restoration response and species had the capacity to increase their populations locally in response to improved habitat quality. This capacity may vary depending on the ecological traits of the species, such as its fecundity, dispersal, competitive ability, and conspecific attraction (Ward & Schlossberg 2004; Rodríguez et al 2007; Mathewson et al 2013) and the proximity of potential source populations; we acknowledge some of these assumptions may not have been met for Willow Flycatcher (Schofield et al 2018) given its declining status throughout our study region and extirpation from much of its former range (Loffland et al 2014). Lastly, it is important that the response curves we report are interpreted within the temporal scale of our study.…”

Harnessing knowledge of animal behavior to improve habitat restoration outcomes

“…2) is intended to be general but can be adapted to identify and mitigate factors that constrain the outcomes of specific restoration projects. To illustrate, we cite work on the Southwestern willow flycatcher (Empidonax traillii extimus; Schofield et al 2018). Californian populations of this species have declined due to massive habitat loss, and habitat restoration efforts are underway to create new habitat (Fig.…”

“…For this species, a lack of vocalizing conspecifics (e.g., missing cues, S4a) is likely to be the cause. Schofield et al (2018) conducted a field experiment, broadcasting flycatcher vocalizations in 14 meadows that had been restored (hydrological restoration through channel filling, plus livestock removal) but were unoccupied, and not broadcasting vocalizations in 19 unrestored control sites. These sites were located close to known breeding populations (so scenarios S2 and S3 were not likely to cause restoration failure).…”

“…The restored sites were selected to have similar vegetation characteristics to known breeding sites to maximize the chance that the animal's habitat requirements are met (step 5). However, in the future, conspecific broadcasts need to be accompanied by monitoring to assess fitness (e.g., nesting success) and multi-year persistence (Schofield et al 2018).…”

“…Information about habitat selection and fitness is vital for assessing success of restoration (Hale et al 2019b), especially when responses are unexpected. For instance, Willow flycatchers (Empidonax traillii) often fail to recolonize sites, regardless of habitat suitability, if these sites lack calling conspecifics (Schofield et al 2018). Alternatively, restoration could create ecological traps (Robertson and Hutto 2006) where individual animals are attracted to restored sites but, once there, suffer reduced fitness (Hale et al 2015, Hale and.…”