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Data from: Lunar synchrony, geography, and individual clocks shape autumn migration timing in an avian migrant
Korpach, Alicia; Davy, Christina; Mills, Alex; Fraser, Kevin — 2023-12-21 <p>Timing programs in animal migrants have been selected to synchronize movements that coincide with predictable resources on the breeding and nonbreeding grounds. Migrants face potential temporal conflicts if their migration schedules benefit from synchrony to conflicting rhythms associated with annual biogeographical (circannual) cues, lunar (circalunar) cues, or individually-repeatable internal clocks. We repeat-tracked individuals of an avian lunaphilic species, Eastern Whip-poor-will (<em>Antrostomus vociferus</em>), for 2–3 successive autumn migrations to determine the influence of the lunar cycle, breeding location, and individual repeatability on migration timing. Almost all birds avoided departing for migration during a full moon, likely to take advantage of the bright moonlight to facilitate visual foraging and enhance pre-migration fattening. However, groups from two latitudinally-distant sampling areas adjusted their autumn departure timing differently relative to the timing of the September full moon, presumably due to differences in seasonal prey availability. Individual repeatability increased throughout autumn migration, suggesting that the factors responsible for shaping migration timing may differ for different migration stages. Our results, that lunar synchrony, local climate, and individual internal clocks appeared to account for much of the variation in migration timing in whip-poor-wills, underscore the value of measuring potentially interacting factors that shape migratory behavior at species, group, and individual levels. It remains unclear if, or how, maintaining individually-repeatable annual migration schedules provides an adaptive benefit for whip-poor-wills or other lunaphilic migrants. Further clarifying the reasons for phenotypic variation in whip-poor-will migration timing will improve predictions of their abilities to adjust migratory movements under changing environmental conditions.</p>
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Population structure, patterns of natal dispersal, and demographic history in a declining aerial insectivore, the purple martin Progne subis
de Greef, Evelien; Brashear, Wesley; Delmore, Kira; Fraser, Kevin — 2022-03-01 <p>Genetic variation is a fundamental component of biodiversity, and studying population structure, gene flow, and demographic history can help guide conservation strategies for many species. Like other aerial insectivores, the purple martin (<em>Progne subis</em>) is in decline, and yet their genetic background remains largely unknown. To address this knowledge gap, we assessed population structure in the nominate eastern subspecies (<em>P. s. subis</em>) with relation to natal dispersal and examined historical genetic patterns in all three subspecies (<em>P. s. subis, P. s. arboricola, P. s. hesperia</em>) across their North American breeding range by estimating effective population sizes over time. We used next-generation sequencing strategies for genomic analyses, integrating whole-genome resequencing data with continent-wide band encounter records to examine natal dispersal. We documented population structure across <em>P. s. subis</em>, with the highest differentiation between the northern (Alberta) and more southern colonies and following patterns of isolation-by-distance. Consistent with spatial patterns of genetic differentiation, we also found greater longitudinal than latitudinal natal dispersal distances, signifying potential latitudinal constraints on gene flow. Earlier contractions in effective population sizes in the western <em>P. s. arboricola</em> and <em>P. s. hesperia</em> compared to the eastern <em>P. s. subis</em> subspecies suggest these subspecies originated from two different glacial refugia. Together, these findings support latitudinal distinction in <em>P. s. subis</em>, and elucidate the origin of subspecies differentiation, highlighting the importance to conserve populations across the range to maximize genetic diversity and adaptive potential in the purple martin.</p>
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Structural and socioeconomic features of cities predict migratory bird species richness
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Kinnunen, Riikka; Fraser, Kevin; Schmidt, Chloé; Garroway, Colin — 2023-12-10 <p>Cities are aggregates of human activities where our decisions shape the environment creating heterogeneity across urban centers that can have significant ecological effects on wildlife. Many bird species are found in cities during the breeding season, which implies they find sufficient resources in cities to support them during this energetically costly time. As populations of many migratory bird species are declining, knowledge of how they are affected by urbanization is needed. Yet, we know little about how the species richness of migratory birds varies across different types of cities. Here we ask if cities' structural and socioeconomic features can predict the species richness of migratory birds that generally select different breeding habitats during the breeding season. We used eBird data from census-designated urban areas in the United States to model the relationship between features of cities (housing density, median income, city age, and commuting time), environmental disturbance (measured by the human footprint index) and species richness by fitting generalized linear models to data. We show that commuting time was the most important factor determining species richness across cities and the rest of the city features were weakly associated with species richness. Overall species were responding to city variation in similar ways.  While we expected that cities with more disturbance would have lower species richness, our results indicate that some species are able to tolerate even highly disturbed cities and that cities in certain regions may act as a refuge to birds. This knowledge is important for our general understanding of cities as habitat for birds and how migratory birds respond to across-city variation during the breeding season.</p>
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Does hatch date set the clock? Timing of post-fledging movements for families of a colonially breeding, long-distance migratory songbird
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Bani Assadi, Saeedeh; Mckinnon, Emily; Cheskey, Ted; Fraser, Kevin — 2022-01-11 <p><span>Factors that influence the development of migration timing in juvenile songbirds have implications for the ability of individuals to respond positively to rapid environmental changes. We investigated the impacts of nest timing on the post-fledging movement timing of juveniles and adults of a migratory songbird. We tested whether first egg date and environmental factors predicted the initiation of post-fledging stages: fledge date for juveniles, and colony departure date for both adults and juveniles. At breeding colonies of purple martin (<i>Progne subis</i>) in southern Ontario, Canada, we monitored nests to determine the date of nest initiation (‘first egg date’) and deployed 122 coded radio-frequency tracking tags on young and adults to determine the timing of post-fledging stages. We found that first egg date, the number of nestmates and age of parents were the main predictors of fledge date. Of these three factors, only first egg date was carried through post-fledge to influence colony departure date for juvenile birds, but this relationship weakened between first egg date and departure date. Nestmates tended to fledge together (range 0-4 days) but exhibited greater variation in colony departure timing (range 0-11 days). Further, while first egg influenced departure date, increasing variation between fledge and departure led to some birds departing breeding colonies at a younger age, suggesting in influence of local environmental factors (e.g. social or photoperiod change) in departure decisions. The timing of adult colony departure date was independent of first egg dates. In sum, our results suggest a role for 1<sup>st</sup> egg dates in setting timing of post-breeding movements, but with variation introduced between fledge and departure dates. Experimental manipulations of photoperiod in a wild setting are needed and future research should investigate whether the timing of movement driven by nesting timing, holds across the rest of migration or even the lifetime of birds. </span></p>

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(auteur : Fraser, Kevin)

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