When to depart from a stopover site? Time since arrival matters more than current weather conditions

Roques, Sébastien; Henry, Pierre‐Yves; Guyot, G.; Bargain, Bruno; Cam, Emmanuelle; Pradel, Roger

doi:10.1101/2020.02.05.933788

Cited by 5 publications

(15 citation statements)

References 80 publications

(191 reference statements)

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“…2015, Roques et al . 2020), such as passerines selecting nights with lower humidity to cross the Gulf of Mexico (Deppe et al . 2015).…”

Section: Discussionmentioning

confidence: 99%

“…2008, Roques et al . 2020). For migrants following a classic model of stopover behaviour of ‘arrive–fatten–depart’, TSA could provide a useful index of an individual's cumulative fuel acquisition and storage, and therefore be predictive of its likelihood of departing from a site.…”

Section: Figurementioning

confidence: 99%

“…2016, Roques et al . 2020). TSA was used as a potential index of cumulative fuel storage, under the classic assumption that stopover activity consists of arrival, fuel storage at a given rate, and departure (Schmaljohann & Eikenaar 2017, Roques et al .…”

Section: Figurementioning

confidence: 99%

“…TSA was used as a potential index of cumulative fuel storage, under the classic assumption that stopover activity consists of arrival, fuel storage at a given rate, and departure (Schmaljohann & Eikenaar 2017, Roques et al . 2020. Daily probabilities of leaving were then modelled with respect to TSA and daily weather conditions.…”

Section: Figurementioning

confidence: 99%

“…Fuelling rates will vary largely as a function of food abundance, predation danger and seasonal time constraints of the individual (Ydenberg & Hope 2019). A potentially useful alternative behavioural metric that might index a bird's fuel status is the time the individual has spent at a stopover site, hereafter 'time since arrival' (TSA; Pledger et al 2008, Roques et al 2020. For migrants following a classic model of stopover behaviour of 'arrive-fatten-depart', TSA could provide a useful index of an individual's cumulative fuel acquisition and storage, and therefore be predictive of its likelihood of departing from a site.…”

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confidence: 99%

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More than just refuelling: lengthy stopover and selection of departure weather by sandpipers prior to transoceanic and transcontinental flights

Roques

Lank

Cam

et al. 2020

Ibis

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The evolutionary and behavioural ecology of migratory birds has received much theoretical and empirical attention. We contribute to this field by contrasting the weather at departure and stopover durations of a long‐distance migratory sandpiper prior to initiating lengthy transoceanic vs. transcontinental flights of potentially variable duration. Transoceanic flights provide few if any stopover options. We predicted that transoceanic migrants should therefore be more selective of energetically favourable weather at departure and have longer stopover durations prior to departing, using time as a surrogate for cumulative fuel acquisition, compared with transcontinental migrants. We used recent advances in capture–recapture modelling to quantify how weather conditions, length of stay, including estimated residence time prior to capture, and age class correlated with daily departure probabilities of Semipalmated Sandpipers Calidris pusilla at a coastal and an inland stopover site at comparable latitude. As expected, departure probabilities from both sites were higher with increasing strength of tailwinds, and the strength of this effect was larger for birds facing transoceanic vs. transcontinental flights. Cloud cover and temperature conditions at departure converged between sites at intermediate values from different background distributions. Stopover durations at both sites were substantially longer than needed if the birds were pursuing a simple tactic of arrive–fatten–leave at the stopover site. We infer that both sites provided high levels of both food and safety relative to other stages in the birds’ annual cycle, favouring lengthy stopovers and subsequent use of lengthy flights from both sites. Our study shows that recent advances of capture–recapture models can provide additional resolution to studies of the migration strategies of birds and refine our perspective on global patterns of migration routes and stopover decisions.

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“…2015, Roques et al . 2020), such as passerines selecting nights with lower humidity to cross the Gulf of Mexico (Deppe et al . 2015).…”

Section: Discussionmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

mentioning

confidence: 99%

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More than just refuelling: lengthy stopover and selection of departure weather by sandpipers prior to transoceanic and transcontinental flights

Roques

Lank

Cam

et al. 2020

Ibis

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Days to visit an offshore island: effect of weather conditions on arrival fuel load and potential flight range for common blackbirds Turdus merula migrating over the North Sea

2021

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Background Crossing open water instead of following the coast(line) is one way for landbirds to continue migration. However, depending on prevailing weather and the birds’ physiological conditions, it is also a risky choice. To date, the question remains as to which interplay between environmental and physiological conditions force landbirds to stop on remote islands. We hypothesise that unfavourable winds affect lean birds with low energy resources, while poor visibility affects all birds regardless of their fuel loads. Methods To test this hypothesis, we caught 1312 common blackbirds Turdus merula stopping over on Helgoland during autumn and spring migration. Arrival fuel load was measured using quantitative magnetic resonance technology. Weather parameters (wind and relative humidity as a proxy for visibility) were interpolated for the night before arrival. Further, we calculated whether caught individuals would have successfully crossed the North Sea instead of landing on Helgoland, depending on wind conditions. Results Both wind and relative humidity the night before arrival were correlated with arrival fuel load. After nights with strong headwinds, birds caught the following day were mostly lean, most of which would not have managed to cross the sea if they had not stopped on Helgoland. In contrast, fat birds that could have successfully travelled on were caught mainly after nights with high relative humidity (≥ 80%). Furthermore, the rate of presumably successful flights was lower due to wind: although only 9% of all blackbirds captured on Helgoland had insufficient fuel loads to allow safe onward migration in still air, real wind conditions would have prevented 30% of birds from successfully crossing the sea during autumn and 21% during spring migration. Conclusions We were able to decipher how physiological condition, wind and relative humidity partially force blackbirds to stop on a remote island. Adverse winds tend to affect lean birds with low energy resources, while poor visibility can affect blackbirds, regardless of whether the arrival fuel load was sufficient for onward flight. Our findings will help to understand different migratory strategies and explain further questions like migration timing.

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Days to Visit an Offshore Island: Effect of Weather Conditions on Arrival Fuel Load and Potential Flight Range for Common Blackbirds Turdus Merula Migrating Over the North Sea

Kelsey

Hüppop

Bairlein

2021

Preprint

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Background: Crossing open water instead of following the coast(line) is one way for landbirds to continue migration. However, depending on prevailing weather and the birds’ physiological condition, it is also a risky choice. To date, the question remains as to which interplay between environmental conditions and physiological condition force landbirds to stop on remote islands. We hypothesise that unfavourable winds would affect lean birds with low energy resources, while poor visibility would affect all birds regardless of their fuel load. Methods: To test this hypothesis, we used data of 1312 Common Blackbirds Turdus merula, caught while stopping over on Helgoland during autumn and spring migration. Arrival fuel load was measured using quantitative magnetic resonance technology. Weather parameters (wind and relative humidity as a proxy for visibility) were interpolated for the night before arrival. Further, we calculated whether caught individuals would have managed to successfully cross the North Sea instead of landing on Helgoland, depending on wind conditions. Results: Both wind and relative humidity the night before arrival were correlated with arrival fuel load. After nights with strong headwinds, birds caught the following day were mostly lean, most of which would not have managed to cross the sea if they had not stopped on Helgoland. On the other hand, fat birds that could have successfully travelled on were caught mainly after nights with high relative humidity (≥ 80%). Furthermore, the rate of presumably successful flights was lower due to wind: although only 9% of all blackbirds captured on Helgoland had insufficient fuel loads to allow safe onward migration in still air, real wind conditions would have prevented 30% of birds from successfully crossing the sea during autumn and 21% during spring migration. Conclusions: We were able to decipher how physiological condition, wind and relative humidity force blackbirds to stop on a remote island. Adverse winds tend to affect lean birds with low energy resources, while poor visibility affects all birds, regardless of whether the arrival fuel load was sufficient for onward flight. Our findings will help to understand different migratory strategies and explain further questions like migration timing.

show abstract

When to depart from a stopover site? Time since arrival matters more than current weather conditions

Cited by 5 publications

References 80 publications

More than just refuelling: lengthy stopover and selection of departure weather by sandpipers prior to transoceanic and transcontinental flights

More than just refuelling: lengthy stopover and selection of departure weather by sandpipers prior to transoceanic and transcontinental flights

Days to visit an offshore island: effect of weather conditions on arrival fuel load and potential flight range for common blackbirds Turdus merula migrating over the North Sea

Days to Visit an Offshore Island: Effect of Weather Conditions on Arrival Fuel Load and Potential Flight Range for Common Blackbirds Turdus Merula Migrating Over the North Sea

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