Migration routes and wintering areas of male Red-winged Blackbirds as determined using geolocators

Authors: Stonefish, Dereck et al.

Year: 2021

Publication: Journal of Field Ornithology

Publication Link: https://onlinelibrary.wiley.com/doi/abs/10.1111/jofo.12373

Keywords: annual movements, blackbirds, geo-logger, land bird migration, migratory pathway, songbird

Abstract: Understanding how birds move through and use landscapes across their annual cycle is a
key goal of migration research. Breeding populations of Red-winged Blackbirds (Agelaius phoeniceus) in the
northern United States and Canada are known to migrate to the southern United States each fall and exhibit
strong fidelity to the same breeding areas each spring. Previous mark–recapture studies of Red-winged
Blackbirds have characterized migratory movements, but these estimates are limited in detail because each bird
is only captured (and located) a few times, with days to months between subsequent captures. Using light-level
geolocators, we tracked 13 male Red-winged Blackbirds across one complete annual cycle to investigate both
their fall and spring migrations. Birds consistently used routes straddling the Central and Mississippi flyways,
with relatively small longitudinal differences between breeding and wintering sites. Fall migration began in late
October to late November, and spring migration began in mid-February to late March. On average, birds
traveled longer distances and had marginally longer migration periods during the spring than the fall, in
contrast to well-established patterns in other songbirds. Route directness was high for most individuals, with
little deviation from the shortest possible migratory routes. Birds occupying the same wetlands during the
breeding season wintered across a relatively wide geographic range of locations in the south-central United
States. Overall, our results improve our understanding of the migratory pathways used by Red-winged
Blackbirds across their annual life cycle. Our results also have implications for understanding which control
strategies are most appropriate for managing populations of Red-winged Blackbirds that cause extensive
damage to sunflower crops in the Northern Great Plains.

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