Stopover optimization in a long-distance migrant: the role of fuel load and nocturnal take-off time in Alaskan northern wheatears (Oenanthe oenanthe)

Schmaljohann, Heiko; Korner‐Nievergelt, Fränzi; Naef‐Daenzer, Beat; Nagel, Rolf; Maggini, Ivan; Bulte, Marc; Bairlein, Franz

doi:10.1186/1742-9994-10-26

Cited by 67 publications

(64 citation statements)

References 64 publications

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“…Also, in our study, northern wheatears set off between 38 and 346 min after sunset (n = 21), cf. Schmaljohann et al (2013). Our results clearly demonstrate that the 10th quantile and the first break point of estimating the start of nocturnal migratory restlessness can be used as a reliable approximation for nocturnal departure time in free-flying birds (Fig.…”

Section: Resultsmentioning

confidence: 60%

“…Only the number of active 15-min intervals of the entire night did not predict sun's elevation at departure (Table 1). Possibly, the activity displayed outside the 1-5.5 h time period after lights off, i.e., the time span in which free-flying northern wheatear set off from Helgoland (Schmaljohann et al 2013), is not indicative of the motivation to depart, as already assumed Eikenaar et al (2014). Also, in our study, northern wheatears set off between 38 and 346 min after sunset (n = 21), cf.…”

Section: Resultsmentioning

confidence: 69%

“…We took the first break point in the time series of each individual as an approximation for the start of the nocturnal migratory restlessness. (c) Total number of 15-min intervals in which a bird showed at least five activity counts for the time frame (1-5.5 h after lights off) corresponding to the time period when radio-tagged northern wheatears left Helgoland in other studies (1-5.5 h after sunset) (Schmaljohann et al 2013), cf. Eikenaar et al (2014); and (d) total number of 15-min intervals in which a bird showed at least five activity counts for the entire night, cf.…”

Section: Start Of Nocturnal Migratory Restlessnessmentioning

confidence: 99%

“…Hence, the departure time within the night together with night length define the time spent flying per night, which has a significant effect on total speed of migration via travel speed (Nilsson et al 2013). Despite its importance for our understanding of how migrants time their movements, we have only little information about nocturnal departure times (Schmaljohann et al 2013).…”

Section: Introductionmentioning

confidence: 99%

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Start of nocturnal migratory restlessness in captive birds predicts nocturnal departure time in free-flying birds

Schmaljohann

Kämpfer

Fritzsch

et al. 2015

Behav Ecol Sociobiol

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In nocturnal songbird migrants, total speed of migration is determined by the time birds stay at stopovers, where they replenish fuel reserves used during previous flights, and by their travel speed. In contrast to factors influencing stopover duration, little is known about individual variation in travel speed which is a combination of birds' ground speed and the time spent flying. The latter is directly affected by nocturnal departure time. Ground speed can be easily tracked, e.g., by radar, but not much is known about when migrants set off within the night, let alone factors influencing its variation. Studying how factors cause variation in nocturnal departure time requires an experimental setup that allows transferring results from indoor experiments, where environmental conditions can be controlled for or manipulated, to the behavior of free-flying birds. Here, we show that the start of nocturnal migratory restlessness "Zugunruhe^of caged songbirds was significantly positively related to their radio-tracked nocturnal departure time the following night. We can now start identifying factors causing individual variation in the start of nocturnal migratory restlessness and transfer these results to departure times within the night. This will improve our understanding of why travel speed, and with that total speed of migration, varies individually and how it is affected by environmental changes.

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Section: Resultsmentioning

confidence: 60%

Section: Resultsmentioning

confidence: 69%

Section: Start Of Nocturnal Migratory Restlessnessmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Start of nocturnal migratory restlessness in captive birds predicts nocturnal departure time in free-flying birds

Schmaljohann

Kämpfer

Fritzsch

et al. 2015

Behav Ecol Sociobiol

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“…Experiments have confirmed higher breakdown of muscle tissues when birds fly long periods at low humidity (Gerson and Guglielmo 2011a), which suggests that there may be a trade-off between energy production and water balance in the use of either fat or protein as an energy store. The occurrence of nocturnal migratory flights in certain species or individuals also suggests the possible existence of non-fuel constraints to migration (Alerstam 2009;Schmaljohann et al 2013) or constraints associated with fuel utilisation during migration such as exposure to high temperatures especially when crossing hot deserts during the day (Klaassen 1996).…”

Section: Introductionmentioning

confidence: 99%

Body reserves in intra-African migrants

Nwaogu

Cresswell

2015

J Ornithol

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Avian migration has been shown to be a life history strategy for surviving environmental resource variability, but it requires increased body reserves for long distance flight. Fat reserves make excellent energy stores for barrier crossing, whereas proteins generate less energy for the same mass of fat but provide water during breakdown, which may become especially useful when birds become water stressed. Intra-African migrants are probably unlikely to have to cross barriers equivalent to the Sahara and the Mediterranean sea and so may have different patterns of mass reserves reflecting the utility of metabolizing fat versus protein in hot, tropical environments. We examined differences in proportions of body mass gain, pectoral muscle score, and fat score between intra-African migrants, Palearctic migrants, and resident African species. We tested whether intra-African migrants show a distinct seasonal peak in mass gain corresponding to expected peak migration period in a manner similar to Palearctic migrants, but maintain larger muscle tissues, because Palearctic migrants are more constrained by a need to heavily up-regulate fat in addition to fat-free reserves before migration due to the energy requirements of crossing the barrier of the Sahara. We found that intra-African migrants had a peak seasonal mass gain similar to Palearctics whereas African residents did not, and that Palearctics increased fat reserves with pectoral muscle reserves, so that they had much higher fat scores for any given level of pectoral muscle compared to intra-African migrants or resident species. Our results suggest that barrier crossing leads to a distinct increase in fat reserves rather than migration per se, and suggests that intra-African migrants are more similar in their reserve management to African residents. Mass gain devoid of visible fat accumulation in intra-African migrants may, therefore, suggest absence of barriers during migration.

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The urge to breed early: Similar responses to environmental conditions in short‐ and long‐distance migrants during spring migration

Rüppel

Hüppop

Schmaljohann

et al. 2023

Ecology and Evolution

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Birds migrating different distances experience different temporal, energetic, physiological, and physical constraints throughout migration, which is reflected in their migration strategy. Consequently, we predict different behavioral decisions to similar environmental cues between short-and long-distance migrants, which has been documented for autumn migration. Here, we focus on the question whether tradeoff decisions regarding departure, routing, and landing when alternating between migratory endurance flights and stopovers also differ during spring migration. As early arrivals at the breeding grounds should be ultimately favored regardless of migration distance, selection may favor more similar behavioral decisions in spring than in autumn. We radio-tagged short-and long-distance migratory songbirds at stopover sites along the German North Sea coast during spring and automatically tracked their migratory behavior using a large-scale network of receiver stations. Once departed, birds could either cross the sea or detour along the coast. We corrected for spatially biased detection data, using a hierarchical multistate model to assess how birds respond to variation in environmental conditions in their day-to-day departure decisions and route selection. The day-to-day departure probability was higher in long-distance migrants independently of the routing decision. Irrespective of migration distance, all species more likely departed under light winds and rainless conditions, while the influence of air pressure change and relative humidity was species-specific. By accounting for detection probabilities, we estimated that about half of all individuals of each species crossed the sea but did not find differences between short-and longdistance migrants. Offshore flights were more likely when winds blew offshore and began earlier within the night compared with onshore flights. Our results suggest that selection more similarly affects birds of different migration distances in spring than in autumn. These findings put the focus toward how ultimate mechanisms may shape departure and routing decisions differently between migration seasons.

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Stopover optimization in a long-distance migrant: the role of fuel load and nocturnal take-off time in Alaskan northern wheatears (Oenanthe oenanthe)

Cited by 67 publications

References 64 publications

Start of nocturnal migratory restlessness in captive birds predicts nocturnal departure time in free-flying birds

Start of nocturnal migratory restlessness in captive birds predicts nocturnal departure time in free-flying birds

Body reserves in intra-African migrants

The urge to breed early: Similar responses to environmental conditions in short‐ and long‐distance migrants during spring migration

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