Phenology of nocturnal avian migration has shifted at the continental scale

Horton, Kyle G.; Sorte, Frank A. La; Sheldon, Daniel; Lin, Tsung‐Yu; Winner, Kevin; Bernstein, Garrett; Maji, Subhransu; Hochachka, Wesley M.; Farnsworth, Andrew

doi:10.1038/s41558-019-0648-9

Cited by 115 publications

(133 citation statements)

References 46 publications

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“…We found that more species exhibited changes in passage duration in fall than in spring demonstrating that the responses of songbirds to environmental change varies within and among species. Our study raises more questions than it answers by suggesting that, contrary to recent predictions, changes in stopover duration do not generate changes in songbird migration phenology (Horton et al, 2020). We conclude that no single factor is most important for changes in migration timing; rather they stem from the interaction of diverse intrinsic and extrinsic factors.…”

Section: Discussioncontrasting

confidence: 84%

Non-parallel changes in songbird migration timing are not explained by changes in stopover duration

Dorian

Lloyd-Evans

Reed

2020

PeerJ

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Shifts in the timing of animal migration are widespread and well-documented; however, the mechanism underlying these changes is largely unknown. In this study, we test the hypothesis that systematic changes in stopover duration—the time that individuals spend resting and refueling at a site—are driving shifts in songbird migration timing. Specifically, we predicted that increases in stopover duration at our study site could generate increases in passage duration—the number of days that a study site is occupied by a particular species—by changing the temporal breadth of observations and vise versa. We analyzed an uninterrupted 46-year bird banding dataset from Massachusetts, USA using quantile regression, which allowed us to detect changes in early-and late-arriving birds, as well as changes in passage duration. We found that median spring migration had advanced by 1.04 days per decade; that these advances had strengthened over the last 13 years; and that early-and late-arriving birds were advancing in parallel, leading to negligible changes in the duration of spring passage at our site (+0.07 days per decade). In contrast, changes in fall migration were less consistent. Across species, we found that median fall migration had delayed by 0.80 days per decade, and that changes were stronger in late-arriving birds, leading to an average increase in passage duration of 0.45 days per decade. Trends in stopover duration, however, were weak and negative and, as a result, could not explain any changes in passage duration. We discuss, and provide some evidence, that changes in population age-structure, cryptic geographic variation, or shifts in resource availability are consistent with increases in fall passage duration. Moreover, we demonstrate the importance of evaluating changes across the entire phenological distribution, rather than just the mean, and stress this as an important consideration for future studies.

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Section: Discussioncontrasting

confidence: 84%

Non-parallel changes in songbird migration timing are not explained by changes in stopover duration

Dorian

Lloyd-Evans

Reed

2020

PeerJ

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“…Migratory flights in many species occur at night, implying a seasonal change in individuals from almost exclusively daytime activity to nocturnal flight. This shift to additional nocturnality is starkly detectable in the wild, for example on a continental scale using weather radars (Horton et al, 2020), and in captivity as migratory restlessness as described above. Recent studies have indeed indicated that strong Zugunruhe associates with higher probability to migrate in the wild (Eikenaar et al, 2014;Mukhin et al, 2018).…”

Section: Diel Timingmentioning

confidence: 89%

Endogenous Programs and Flexibility in Bird Migration

Åkesson

Helm

2020

Front. Ecol. Evol.

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Endogenous programs that regulate annual cycles have been shown for many taxa, including protists, arthropods, fish, mammals and birds. In migration biology, these programs are best known in songbirds. The majority of songbirds rely on a genetic program inherited from their parents that will guide them during their first solo-migration. The phenotypic components of the program are crucial for their individual fitness and survival, and include time components, direction, and distance. This program is constructed to both guide behavior and to regulate flexible responses to the environment at different stages of the annual cycle. The migration program is driven by a circannual rhythm, allowing for, and resetting, carry-over effects. With experience, the migration decisions of individual migrants may be based on information learnt on breeding sites, wintering sites, and en route. At the population level, substantial variation in route choice and timing of migration may be explained by inherited variation of program components, by interactions with environmental and social factors, and by individual learning. In this review we will explore the components of endogenous migration programs and discuss in what ways they can lead to flexibility and variation in migration behavior.

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“…when bird velocities exceed the radar pulse repetition frequency) following Sheldon et al (2013). We classified and removed weather contamination using MistNet (Lin et al, 2019) and then constructed vertical profiles of mean reflectivity from 0 to 3 km above ground level in 0.1 km height bins from the five lowest elevation scans in 5-37.5 km around each radar (Sheldon, 2015;Horton et al, 2020).…”

Section: Radar Data Processingmentioning

confidence: 99%

A place to land: spatiotemporal drivers of stopover habitat use by migrating birds

et al. 2020

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Migrating birds require en route habitats to rest and refuel. Yet, habitat use has never been integrated with passage to understand the factors that determine where and when birds stopover during spring and autumn migration. Here, we introduce the stopover-to-passage ratio (SPR), the percentage of passage migrants that stop in an area, and use 8 years of data from 12 weather surveillance radars to estimate over 50% SPR during spring and autumn through the Gulf of Mexico and Atlantic coasts of the southeastern US, the most prominent corridor for North America's migratory birds. During stopovers, birds concentrated close to the coast during spring and inland in forested landscapes during autumn, suggesting seasonal differences in habitat function and highlighting the vital role of stopover habitats in sustaining migratory communities. Beyond advancing understanding of migration ecology, SPR will facilitate conservation through identification of sites that are disproportionally selected for stopover by migrating birds.

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Phenology of nocturnal avian migration has shifted at the continental scale

Cited by 115 publications

References 46 publications

Non-parallel changes in songbird migration timing are not explained by changes in stopover duration

Non-parallel changes in songbird migration timing are not explained by changes in stopover duration

Endogenous Programs and Flexibility in Bird Migration

A place to land: spatiotemporal drivers of stopover habitat use by migrating birds

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