Insights on post-breeding movements from a northeastern population of Canada Warblers (Cardellina canadensis)

Authors: Camille Bégin-MarchandFrançois GagnonBruno DroletJacques Ibarzabal, and Junior A. Tremblay

Year: 2022

Publication: Avian Conservation & Ecology

Publication Link:

Keywords: migration routes; Motus; neotropical migrants; radio-telemetry; residence time

Abstract: The study of migratory songbird transition periods, such as the post-breeding period, is complex because birds undertake
different types of movements that vary in space and time. Nonetheless, it is important to understand the extent and duration of the
territory and specific sites use to identify human activities likely to affect the species’ survival. Individuals from different regional
populations may exhibit specific movements during the various phases of their annual cycle, and therefore conservation actions must
be adapted. We studied a population of Canada Warblers (Cardellina canadensis) from the Saguenay region of Quebec, Canada, in the
northeastern part of the species’ breeding range. We used a coordinated radio-telemetry network (Motus) to determine the residence
time within the breeding territory, dates and times of departure, and early fall migration routes of 18 adult birds. We expected individuals
to leave by mid-August and to migrate through the eastern flyway, along the Atlantic Coast. Six tracked individuals remained on their
breeding territory until early September, corresponding to a residence time of approximately 90 days. These individuals left just after
sunset on their day of departure. Twelve individuals departed earlier, and in the daytime, before the end of August; their earlier departure
was likely for a purpose other than migration. Nine individuals were detected outside their breeding territory along the Atlantic
migratory flyway: four migrated through the Great Lakes region, one in the Great Appalachian Valley, three along the Atlantic Coast
or coastal plain, and one with an undetermined route. Our results suggest that adult Canada Warblers remain in the Saguenay region
longer than expected, and that, although some individuals remain close to their breeding territory during the post-breeding period,
others may use surrounding territories prior to initiating their fall migration. Our results will allow regional conservation managers to
recommend that regional industry postpone the timing of certain activities that could negatively affect the species’ survival. Our study
highlights the importance of fine-scale studies focused on specific periods of migratory songbird annual cycles to fill important
knowledge gaps for understanding of the ecology of their species.

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