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

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Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues? / Dokter, Adriaan M.; Åkesson, Susanne; Beekhuis, Hans; Bouten, Willem; Buurma, Luit; van Gasteren, Hans; Holleman, Iwan.

In: Animal Behaviour, Vol. 85, No. 3, 2013, p. 545-552.

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Dokter, AM, Åkesson, S, Beekhuis, H, Bouten, W, Buurma, L, van Gasteren, H & Holleman, I 2013, 'Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?', Animal Behaviour, vol. 85, no. 3, pp. 545-552. https://doi.org/10.1016/j.anbehav.2012.12.006

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Dokter, Adriaan M. ; Åkesson, Susanne ; Beekhuis, Hans ; Bouten, Willem ; Buurma, Luit ; van Gasteren, Hans ; Holleman, Iwan. / Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?. In: Animal Behaviour. 2013 ; Vol. 85, No. 3. pp. 545-552.

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TY - JOUR

T1 - Twilight ascents by common swifts, Apus apus, at dawn and dusk: acquisition of orientation cues?

AU - Dokter, Adriaan M.

AU - Åkesson, Susanne

AU - Beekhuis, Hans

AU - Bouten, Willem

AU - Buurma, Luit

AU - van Gasteren, Hans

AU - Holleman, Iwan

PY - 2013

Y1 - 2013

N2 - Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of sunset and sunrise, suggesting that the acquisition of twilight-specific light-based cues plays an important role in the progression of the ascents. Ascent height was well explained by the altitude of the 280 K isotherm, and was not significantly related to wind, cloud base height, humidity or the presence of nocturnal insects. We hypothesize that swifts profile the state of the atmospheric boundary layer during twilight ascents and/or attempt to maximize their perceptual range for visual access to distant horizontal landmarks, including surrounding weather. We compare twilight profiling by swifts with vertical twilight movements observed in other taxa, proposed to be related to orientation and navigation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

AB - Common swifts are specialist flyers spending most of their life aloft, including night-time periods when this species roosts on the wing. Nocturnal roosting is preceded by a vertical ascent in twilight conditions towards altitudes of up to 2.5 km, behaviour previously explained as flight altitude selection for sleeping. We examined the nocturnal flight behaviour of swifts, as uniquely identified by a Doppler weather radar in central Netherlands using continuous measurements during two consecutive breeding seasons. Common swifts performed twilight ascents not only at dusk but also at dawn, which casts new light on the purpose of these ascents. Dusk and dawn ascents were mirror images of each other when time-referenced to the moment of sunset and sunrise, suggesting that the acquisition of twilight-specific light-based cues plays an important role in the progression of the ascents. Ascent height was well explained by the altitude of the 280 K isotherm, and was not significantly related to wind, cloud base height, humidity or the presence of nocturnal insects. We hypothesize that swifts profile the state of the atmospheric boundary layer during twilight ascents and/or attempt to maximize their perceptual range for visual access to distant horizontal landmarks, including surrounding weather. We compare twilight profiling by swifts with vertical twilight movements observed in other taxa, proposed to be related to orientation and navigation. (C) 2012 The Association for the Study of Animal Behaviour. Published by Elsevier Ltd. All rights reserved.

KW - Apus apus

KW - atmospheric assessment

KW - celestial cue

KW - common swift

KW - flight

KW - altitude

KW - orientation

KW - navigation

KW - twilight

KW - weather radar

U2 - 10.1016/j.anbehav.2012.12.006

DO - 10.1016/j.anbehav.2012.12.006

M3 - Article

VL - 85

SP - 545

EP - 552

JO - The British Journal of Animal Behaviour

JF - The British Journal of Animal Behaviour

SN - 1095-8282

IS - 3

ER -