10.5061/DRYAD.M905QFV1W
Norevik, Gabriel
0000-0002-4112-0346
Lund University
Åkesson, Susanne
Lund University
Andersson, Arne
Lund University
Bäckman, Johan
Lund University
Hedenström, Anders
Lund University
Flight altitude dynamics of migrating European nightjars across regions
and seasons
Dryad
dataset
2021
FOS: Biological sciences
Caprimulgus europaeus
ascent
descent
exploratory movement
individual-based tracking
Wind
Swedish Research Council
https://ror.org/03zttf063
621-2012-3585, 2016-03625; 621-2013-4361, 349-2007-8690
2021-10-19T00:00:00Z
2021-10-19T00:00:00Z
en
16655630 bytes
3
CC0 1.0 Universal (CC0 1.0) Public Domain Dedication
Avian migrants may fly at a range of altitudes, but usually concentrate
near strata where a combination of flight conditions is favourable. The
aerial environment can have a large impact on the performance of the
migrant and is usually highly dynamic, making it beneficial for the bird
to regularly check the flight conditions at alternative altitudes. We
recorded the migrations between northern Europe and sub-Saharan Africa of
European nightjars Caprimulgus europaeus to explore their altitudinal
space use during spring and autumn flights to test whether their climbs
and descents were performed according to predictions from flight
mechanical theory. The nightjars commonly operated at ascent rates below
the theoretical maximum, and periods of descent were commonly undertaken
by active flight, and rarely by energetically cheaper gliding flight,
allowing the birds to sink at lower rates than possible during a best
glide scenario. Spring migration across all regions was associated with
more exploratory vertical flights involving major climbs, a higher degree
of vertical displacement within flights, and less time spent in level
flight, although flight altitude per se was only higher during the Sahara
crossing. This study demonstrates a surprisingly frequent use of slow
vertical displacements during migratory flights of a long-distance avian
migrant and show how these behaviours vary between seasons and regions,
presumably in response to different flight conditions. The results should
inspire future studies on the potential costs associated with frequent
altitude changes and their trade-offs against anticipated flight condition
improvements for aerial migrants.
Data files in plain text containing detailed accelerometer, pressure and
temperature data recorded on European nightjars Caprimulgus europaeus.
Files containing activity data: For each timestamp the distribution of 12
activity registrations are presented in columns Act0 to Act10 (Act0 to
Act5 for activity data 2018-2019) that represent a range of activity
levels given a predefined sampling routine. See, methods and supplement in
the related work. Column “check” is the sum of all activity counts and
should be 12 if sampling worked as intended. Id represents each
datalogger. The pressure data file contains a timestamp following the
recorded temperature in °C and barometric pressure in mbar.