Unexplained altitude changes in a migrating thrush: Long-flight altitude data from radio-telemetry

Bowlin, Melissa S.; Enstrom, David A.; Murphy, Brian J.; Plaza, Edward; Jurich, Peter; Cochran, James S.

doi:10.1642/auk-15-33.1

Cited by 29 publications

(30 citation statements)

References 26 publications

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“…Likewise, both the red-backed shrike and the great reed warbler in this study changed flight altitudes several times during their nocturnal flights, clearly illustrating that songbird migrants do not maintain a constant (preferred) cruising altitude, as has often been assumed in migration models (Alerstam 1990, Newton 2008, Pennycuick 2008. The resolution of one estimate per hour cannot be used to show the frequent changes in altitudes recorded in high resolution data of single flights (Bowlin et al 2015). However, our data support the observations of a complex behaviour with surprising changes of flight altitudes.…”

Section: Flight Altitudessupporting

confidence: 49%

“…to a highly significant degree (Liechti and Bruderer 1998). Swainson's thrushes tracked during their migratory flights made extensive adjustments in flight altitudes (>100 m) regularly during the flight (Bowlin et al 2015). Changes in wingbeat frequency indicated that the variations were active changes in altitude made by the birds, but the reasons for these changes are yet to be understood.…”

Section: Flight Altitudesmentioning

confidence: 99%

“…The first high resolution altitudinal tracks came with GPS satellite receivers, but these receivers are still too heavy to be carried by a small songbird (Bridge et al 2011). Miniaturized barometric pressure sensors were first used in a radiotelemetry study where Swainson's thrushes were tracked during entire nights of flight with high temporal resolution (every 15-30 s; Bowlin et al 2015). Those tracks clearly illustrated a complexity in altitudinal flight behaviour that previously had been completely unknown due to the difficulties in studying individual flight behaviour.…”

Section: Introductionmentioning

confidence: 99%

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Barometer logging reveals new dimensions of individual songbird migration

Sjöberg

Pedersen

Malmiga

et al. 2018

Journal of Avian Biology

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Recent advances in tracking technology are based on the use of miniature sensors for recording new aspects of individual migratory behaviour. In this study, we have used activity data loggers with barometric and temperature sensors to record the flight altitudes as well as ground elevations during stationary periods of migratory songbirds. We tracked one individual of red‐backed shrike and one great reed warbler along their autumn migration from Europe to Africa. Both individuals performed their migration stepwise in travel segments and climbed most metres during the passage across the Mediterranean Sea and the Sahara Desert and least metres during the first flight segment in Europe. The great reed warbler reached its highest flight altitude of 3950 m a.s.l. during the travel segment from Europe to west Africa, while the red‐backed shrike reached 3650 m a.s.l as maximum flight altitude during its travel segment from Sahel to southern Africa. Both individuals used both lowlands and highlands for resting periods along their migrations. Furthermore, temperature decreased with increasing altitude during migratory flights for both individuals, highlighting the potential to determine flight duration from temperature measurements. Finally, we discuss how barometric data could be used to investigate birds’ responses to changes in air pressure as a cue for departures on migratory flights. This new technique, i.e. using a miniature data logger with barometric pressure sensor to estimate flight altitudes and ground elevations, will open up new avenues for research and importantly advance our understanding on how small birds behave during migratory flights.

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Section: Flight Altitudessupporting

confidence: 49%

Section: Flight Altitudesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Barometer logging reveals new dimensions of individual songbird migration

Sjöberg

Pedersen

Malmiga

et al. 2018

Journal of Avian Biology

View full text Add to dashboard Cite

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“…This suggests, as postulated by Bowlin et al . (), that birds are drawn to these unintentional beacons during migratory flight at a broad scale. Moreover, our results validate experimental evidence that caged migratory birds orient towards the skyglow of cities (Gauthreaux ).…”

Section: Discussionmentioning

confidence: 99%

Artificial light at night confounds broad‐scale habitat use by migrating birds

et al. 2018

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With many of the world's migratory bird populations in alarming decline, broad-scale assessments of responses to migratory hazards may prove crucial to successful conservation efforts. Most birds migrate at night through increasingly light-polluted skies. Bright light sources can attract airborne migrants and lead to collisions with structures, but might also influence selection of migratory stopover habitat and thereby acquisition of food resources. We demonstrate, using multi-year weather radar measurements of nocturnal migrants across the northeastern U.S., that autumnal migrant stopover density increased at regional scales with proximity to the brightest areas, but decreased within a few kilometers of brightly-lit sources. This finding implies broad-scale attraction to artificial light while airborne, impeding selection for extensive forest habitat. Given that high-quality stopover habitat is critical to successful migration, and hindrances during migration can decrease fitness, artificial lights present a potentially heightened conservation concern for migratory bird populations.

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“…It is possible to account for these heterogeneous altitude distributions between land and sea by estimating a separate vertical profile above the sea if the radar is sufficiently close to water. Furthermore, birds might follow the contours of the landscape and fly at a constant altitude above ground level, while in other cases, birds may maintain a constant altitude above mean sea level regardless of the underlying topography, e.g., [13,19,40]. Since the elevation of the terrain can change considerably over the area of observation, this might create inaccuracies in the VID estimate.…”

Section: Discussionmentioning

confidence: 99%

High-Resolution Spatial Distribution of Bird Movements Estimated from a Weather Radar Network

et al. 2020

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Weather radars provide detailed information on aerial movements of organisms. However, interpreting fine-scale radar imagery remains challenging because of changes in aerial sampling altitude with distance from the radar. Fine-scale radar imagery has primarily been used to assess mass exodus at sunset to study stopover habitat associations. Here, we present a method that enables a more intuitive integration of information across elevation scans projected in a two-dimensional spatial image of fine-scale radar reflectivity. We applied this method on nights of intense bird migration to demonstrate how the spatial distribution of migrants can be explored at finer spatial scales and across multiple radars during the higher flying en-route phase of migration. The resulting reflectivity maps enable explorative analysis of factors influencing their regional and fine-scale distribution. We illustrate the method’s application by generating time-series of composites of up to 20 radars, achieving a nearly complete spatial coverage of a large part of Northwest Europe. These visualizations are highly useful in interpreting regional-scale migration patterns and provide detailed information on bird movements in the landscape and aerial environment.

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Unexplained altitude changes in a migrating thrush: Long-flight altitude data from radio-telemetry

Cited by 29 publications

References 26 publications

Barometer logging reveals new dimensions of individual songbird migration

Barometer logging reveals new dimensions of individual songbird migration

Artificial light at night confounds broad‐scale habitat use by migrating birds

High-Resolution Spatial Distribution of Bird Movements Estimated from a Weather Radar Network

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