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Studies on the migratory behavior of songbirds are important to inform full annual cycle conservation. We remotely tracked the early fall migratory movements of both juvenile and adult Savannah Sparrows (Passerculus sandwichensis) that were tagged on their natal/breeding territories in southwestern Ontario, Canada, where the Motus Wildlife Tracking System has the highest density of automated receivers in North America. Our primary aims were to describe and compare adult and juvenile migratory movements during the early part of migration, compare frequency of detection of juveniles versus adults as a proxy for minimum apparent survival, and describe potential migration routes and overwintering areas. Juveniles initiated migration approximately a month earlier than adults. Both juveniles and adults typically made their first migratory flight in a southwest direction, but some juveniles displayed subsequent exploratory movements that were not in a southwest direction, potentially to collect information for next year's breeding site selection. Detection rates early in migration were similar, but low, for adults and juveniles (34% and 39% respectively), suggesting that juveniles that had survived the fledgling period likely did not experience high mortality during the subsequent 2 months prior to their fall migration. Long-distance detections of 2 adults preliminarily suggest that individuals from this southern Ontario breeding region may travel west of the Appalachian Mountains along the Mississippi flyway during fall migration. Our study aligns with previously reported patterns of age-specific migratory behavior from other Savannah Sparrow populations and contributes to our overall understanding of the migratory ecology of this species. [ABSTRACT FROM AUTHOR]

Radiotelemetry is an essential method for studying the movements and survival of cryptic grassland bird fledglings. There is mixed evidence on the effects of wearing radio‐transmitters for passerines, with negative consequences probably under‐reported. In one season of a 2‐year study, we found 23% of radio‐transmitters and/or antennas deployed on fledgling Savannah Sparrows Passerculus sandwichensis had become entangled in vegetation, consequently harming the fledglings in two of seven cases. It is important for researchers to share their information on any negative consequences of attaching radio‐transmitters to songbirds in order to improve methods and to harm fewer individuals in future studies. [ABSTRACT FROM AUTHOR]