Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?

Dokter, Adriaan M.; Åkesson, Susanne; Beekhuis, Hans; Bouten, W.; Buurma, Luit; Gasteren, Hans van; Holleman, Iwan

doi:10.1016/j.anbehav.2012.12.006

Cited by 44 publications

(58 citation statements)

References 37 publications

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“…This gives a hint, that aerial roosting is driven by food availability, which might restrict aerial roosting of the large Alpine swifts to the equatorial region. A dawn and dusk ascent described recently for common swifts 21 let us assume that the observed increase in activity at dawn and dusk implies a corresponding ascent in the Alpine swifts. The function of such an ascent is not clear yet.…”

Section: Discussionmentioning

confidence: 99%

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First evidence of a 200-day non-stop flight in a bird

et al. 2013

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Being airborne is considered to be energetically more costly as compared with being on the ground or in water. Birds migrating or foraging while airborne are thought to spend some time resting on the ground or water to recover from these energetically demanding activities. However, for several decades ornithologists have claimed that some swifts may stay airborne for almost their whole lifetime. Here we present the first unequivocal evidence that an individual bird of the Alpine swift (Tachymarptis melba) can stay airborne for migration, foraging and roosting over a period of more than 6 months. To date, such long-lasting locomotive activities had been reported only for animals living in the sea. Even for an aerodynamically optimized bird, like the Alpine swift, flying requires a considerable amount of energy for continuous locomotive control. Our data imply that all vital physiological processes, including sleep, can be perpetuated during flight.

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Section: Discussionmentioning

confidence: 99%

“…The function of such an ascent is not clear yet. Based on the radar data, which also recorded insect densities, it could be ruled out that the ascent was related to foraging 21 .…”

Section: Discussionmentioning

confidence: 99%

First evidence of a 200-day non-stop flight in a bird

et al. 2013

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“…Interestingly, around dusk swifts ascend to 2.5 km and then gradually descend during the middle of the night [25]. Alone this might suggest that high altitudes are attained to provide an altitudinal buffer for the safe occurrence of sleep.…”

Section: Apodiformes (Swifts and Hummingbirds) 221 Swiftsmentioning

confidence: 99%

“…Alone this might suggest that high altitudes are attained to provide an altitudinal buffer for the safe occurrence of sleep. However, swifts also return to similarly high altitudes around dawn suggesting that ascents rsfs.royalsocietypublishing.org Interface Focus 7: 20160082 serve other functions, such as assessing approaching weather conditions [25].…”

Section: Apodiformes (Swifts and Hummingbirds) 221 Swiftsmentioning

confidence: 99%

Sleeping on the wing

Rattenborg¹

2017

Interface Focus.

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Wakefulness enables animals to interface adaptively with the environment. Paradoxically, in insects to humans, the efficacy of wakefulness depends on daily sleep, a mysterious, usually quiescent state of reduced environmental awareness. However, several birds fly non-stop for days, weeks or months without landing, questioning whether and how they sleep. It is commonly assumed that such birds sleep with one cerebral hemisphere at a time (i.e. unihemispherically) and with only the corresponding eye closed, as observed in swimming dolphins. However, the discovery that birds on land can perform adaptively despite sleeping very little raised the possibility that birds forgo sleep during long flights. In the first study to measure the brain state of birds during long flights, great frigatebirds ( Fregata minor ) slept, but only during soaring and gliding flight. Although sleep was more unihemispheric in flight than on land, sleep also occurred with both brain hemispheres, indicating that having at least one hemisphere awake is not required to maintain the aerodynamic control of flight. Nonetheless, soaring frigatebirds appeared to use unihemispheric sleep to watch where they were going while circling in rising air currents. Despite being able to engage in all types of sleep in flight, the birds only slept for 0.7 h d −1 during flights lasting up to 10 days. By contrast, once back on land they slept 12.8 h d −1 . This suggests that the ecological demands for attention usually exceeded that afforded by sleeping unihemispherically. The ability to interface adaptively with the environment despite sleeping very little challenges commonly held views regarding sleep, and therefore serves as a powerful system for examining the functions of sleep and the consequences of its loss.

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“…The lower foraging intensity at midday may be a consequence of swiftlets being aerial feeders and nonstop flyers; swiftlets can climb to higher altitudes around midday using thermal lifts to conserve energy but showed little evidence of foraging. Alternatively, swiftlets might follow insects carried by rising air currents, as do migratory swifts (Dokter et al, 2013), but we need more observations at heights of over 100 m to confirm this. However, purple martin (Progne subis), an aerial insectivore which can fly up to 1,889 m above the ground, nevertheless mostly forage below 200 m, where their prey occur (Helms, Godfrey, Ames, & Bridge, 2016).…”

Section: Diurnal and Seasonal Variation In Foraging Intensitymentioning

confidence: 99%

Wetland, Forest, and Open Paddy Land Are the Key Foraging Habitats for Germain’s Swiftlet (Aerodramus inexpectatus germani) in Southern Thailand

Petkliang

Gale

Brunton

et al. 2017

Tropical Conservation Science

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Germain's swiftlets (Aerodramus inexpectatus germani) are farmed regularly in Southeast Asia and produce highly valuable nests for which there is an increasing demand. Some populations of this species are thought to be decreasing, but little is known about the habitat used by swiftlets for foraging. Here, we focused on this swiftlet's foraging habitat selection and describe their daily and seasonal variations in habitat use. We predict that the prey capture attempts would be highest during twilight periods of each day, but that overall capture rates would vary with season and habitat type. Prey capture attempts at different times of the day and seasons in five different habitats were investigated and compared to flying insect availability (estimate as biomass). For each habitat, insects were trapped immediately 5-10 m above vegetation levels (i.e., tree canopy and open paddies) and 0-5 m above water surfaces in water body habitat. The highest foraging intensity occurred over water bodies, forest, and open paddy land; all of which contained high numbers of major prey insects (Hymenoptera, Diptera, and Hemiptera). Foraging during the wet season was at a greater intensity than during the dry season which was associated with increased insect availability. This suggested that food supply in each habitat type, time of day, and season influenced the bird's foraging habitat use. To conserve populations of this swiftlet, it is therefore important to protect wetlands, forest areas, and open paddy land to support natural insect prey within the foraging range of local swiftlets.

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Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?

Cited by 44 publications

References 37 publications

First evidence of a 200-day non-stop flight in a bird

First evidence of a 200-day non-stop flight in a bird

Sleeping on the wing

Wetland, Forest, and Open Paddy Land Are the Key Foraging Habitats for Germain’s Swiftlet (Aerodramus inexpectatus germani) in Southern Thailand

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