Ken A. Otter

Domestic cats ( Felis catus ) are well-loved companion animals; however, cats easily become unsocialized if abandoned. Abandonment amplifies human concerns over increased predation on local wildlife and disease transmission to housed companion animals. Thus, attention must be given to limiting the “creation” of feral/unsocialized cats while also humanely managing existing cats within municipalities. To understand public attitudes toward domestic cats, including feral/unsocialized cats, a study was undertaken in Prince George, British Columbia, utilizing an online survey, with a mix of close- and open-ended questions. Results identified concerns about unsocialized/feral cats, including disease transmission, damage to private property, and killing birds. In response, spaying/neutering was strongly supported, as well as active management of feral colonies by responsible parties. The elimination of feral colonies, in contrast, was not widely supported; respondents called for compassion in any management approach, arguing for an organized, community-based solution. Examples of such an approach are considered.

For song variants to spread among widely separated breeding populations by cultural evolution, song sharing would have to occur in locations where birds physically overlap in time and space, such as common wintering grounds and/or migratory routes. To identify such spatiotemporal links between populations, we used the Motus Wildlife Tracking System to investigate whether White-throated Sparrows (Zonotrichia albicollis) in three disparate breeding populations in British Columbia migrate to common wintering grounds and overlap on migration pathways. We also tracked sparrows overwintering in a single eastern region (Georgia, United States) to determine whether they disperse to multiple breeding regions. Except for a single sparrow that migrated to California, all other sparrows tagged on western breeding grounds (N = 23) were either detected in, or converging on, the south-central United States. Further, we detected a common migratory pathway tracking the southern edge of the boreal forests in Canada and the western edge of the Eastern Temperate Forests in the United States. This migratory route coincides with regions where previous studies have shown the rapid spread of novel song variants (doublet-ending songs) over short time scales; birds share not only a common wintering ground, but also a common migratory pathway that might reinforce song sharing if song learning extends into the bird’s first spring. Along with learning biases, this could explain the rapid, widespread adoption of novel song variants within the past two decades across western and central Canada. We confirmed that birds from a single wintering location in Georgia dispersed across a wide region during northward migration, which also corresponds to locations where other song variants (triplet-ending) have persisted.

Human habitat disturbances can promote hybridization between closely related, but typically reproductively isolated, species. We explored whether human habitat disturbances are related to hybridization between two closely related songbirds, black‐capped and mountain chickadees, using both genomic and citizen science data sets. First, we genotyped 409 individuals from across both species' ranges using reduced‐representation genome sequencing and compared measures of genetic admixture to a composite measure of human landscape disturbance. Then, using eBird observations, we compared human landscape disturbance values for sites where phenotypically diagnosed hybrids were observed to locations where either parental species was observed to determine whether hybrid chickadees are reported in more disturbed areas. We found that hybridization between black‐capped and mountain chickadees positively correlates with human habitat disturbances. From genomic data, we found that (1) hybrid index (HI) significantly increased with habitat disturbance, (2) more hybrids were sampled in disturbed habitats, (3) mean HIs were higher in disturbed habitats versus wild habitats, and (4) hybrids were detected in habitats with significantly higher disturbance values than parentals. Using eBird data, we found that both hybrid and black‐capped chickadees were significantly more disturbance‐associated than mountain chickadees. Surprisingly, we found that nearly every black‐capped chickadee we sampled contained some proportion of hybrid ancestry, while we detected very few mountain chickadee backcrosses. Our results highlight that hybridization between black‐capped and mountain chickadees is widespread, but initial hybridization is rare (few F1s were detected). We conclude that human habitat disturbances can erode pre‐zygotic reproductive barriers between chickadees and that post‐zygotic isolation is incomplete. Understanding what becomes of recently hybridizing species following large‐scale habitat disturbances is a new, but pressing, consideration for successfully preserving genetic biodiversity in a rapidly changing world.

A diverse landscape can support a more diverse range of species and allow for more complex community structures. In forested habitats, openings and changes in tree composition allow for a higher species richness due to the greater chance of niche occupancy. Knowledge about these relationships may be useful for adapting forest harvesting strategies to, for example, support bird diversity conservation and studies are required to understand how different harvesting strategies influence forest structure and bird diversity. Here, we used Autonomous Recording Units (ARU) to record dawn signalling of forest birds between two forest-harvesting treatment types (complete clear-cuts and hardwood-retention patches) vs control forest patches in the John Prince Research Forest, British Columbia, Canada. We compared Species Richness and Shannon diversity as detected through identifying species in audio recordings, across treatments. The observed Species Richness and Shannon diversity did differ between the Retention treatment and Forest controls when controlling for number of individuals sampled, but both had higher Species Richness and Shannon diversity of passerine species than the Clear-cut treatments. When comparing species composition, we found that forest-associated species were disproportionately detected in Forest controls compared to Clear-cut treatments but detected at intermediate levels in Retention treatments. Species associated with early-seral habitats, though, had disproportionate detection in Clear-cut treatments compared to Forest controls, but also showed expected detections in Retention treatments. These results suggest that partial harvesting and retention of non-commercial hardwoods, can help retain forest-associated species while also helping attract early-seral avian species; this can help increase the overall diversity of the landscape while still making logging profitable. Further research should be conducted to determine the value of this retained habitat at different spatial scales to understand the impacts that it may have for larger-scale deployment.

Both abiotic and biotic drivers influence species distributions. Abiotic drivers such as climate have received considerable attention, even though biotic drivers such as hybridization often interact with abiotic drivers. We sought to explore the (1) costs of co‐occurrence for ecologically similar species that hybridize and (2) associations between ecological factors and condition to understand how abiotic and biotic factors influence species distributions. For two closely related and ecologically similar songbirds, black‐capped and mountain chickadees, we characterized body condition, as a proxy for fitness, using a 1358‐individual range‐wide dataset. We compared body condition in sympatry and allopatry with several abiotic and biotic factors using species‐specific generalized linear mixed models. We generated genomic data for a subset of 217 individuals to determine the extent of hybridization‐driven admixture in our dataset. Within this data subset, we found that ~11% of the chickadees had hybrid ancestry, and all hybrid individuals had typical black‐capped chickadee plumage. In the full dataset, we found that birds of both species, independent of demographic and abiotic factors, had significantly lower body condition when occurring in sympatry than birds in allopatry. This could be driven by either the inclusion of cryptic, likely poor condition, hybrids in our full dataset, competitive interactions in sympatry, or range edge effects. We are currently unable to discriminate between these mechanisms. Our findings have implications for mountain chickadees in particular, which will encounter more black‐capped chickadees as black‐capped chickadee ranges shift upslope and could lead to local declines in mountain chickadee populations.

Anti-predator behaviour is common among birds, but little research exists on whether differences in the predator landscape between urban and rural habitats results in differential anti-predator behaviour. We compared nest-defence behaviour of mountain chickadees ( Poecile gambeli ) in urban and rural habitats in Kamloops, BC, Canada to a simulated predator model (snake) on top of nest boxes while incubating females were away from nests on foraging bouts. Upon their return, we recorded proximity to the predator model, latency to contact the nest box and enter the nest, and number of gargle and chick-a-dee calls as measures of anti-predator behaviour and compared multivariate “predator aversion scores” across birds occupying either rural or urban landscapes. Rural-nesting birds had more aversive reactions to the predator model than the urban-nesting birds, which may suggest differences in perceived threat of the model, in combination with increased boldness associated with urban-nesting birds.

Anthropogenic noise can mask avian vocalizations, and several urban‐dwelling species adjust frequency or amplitude of vocalizations in ways that appear to compensate for increased noise levels. Playback studies have investigated whether receivers differentiate between signals produced by rural and urban males, but it is difficult to determine whether differential response to stimulus reflects differences in audibility versus perceived differences in male signals/condition that result from urban settlement. Here, we performed paired‐playback trials to determine whether mountain chickadees (Poecile gambeli) differentiate urban versus rural songs when both stimuli were broadcast within noise. For each playback, stimuli were played in short bouts starting at a low signal‐to‐noise ratio and increasing in relative amplitude with each successive bout. If the primary function of adjusted urban songs is propagation in noise, we hypothesized that focal males would respond sooner to urban versus rural playbacks (detect at lower signal‐to‐noise ratios). If urban songs solely encode information about the male's condition (such as increased aggression), then we predicted only a differential aggressive response to playbacks once detected. If urban songs both increase propagation and embed information on male condition, we predicted a combination of both response types. We found no difference in latency to first response in urban versus rural songs, but some evidence for differential aggression to playback dependent on both stimulus type (urban vs. rural) and local ambient noise levels; focal males in noisy (urban) sites responded aggressively to both stimulus types, whereas focal males in quiet (rural) sites responded more aggressively to urban than to rural stimuli. This context‐dependent discrimination may be the result of increased aggression in urban habitats, improved communication in noisy habitats by urban signallers and receivers, or some combination of the two.

D’Entremont, M. V., M. I. Hartley, and K. A. Otter. 2017. Comparing pre- versus postoperational movement of nocturnal migrants around a wind energy facility in northeast British Columbia, Canada. Avian Conservation and Ecology 12(2):3. https://doi.org/10.5751/ACE-01046-120203