DOI: 10.5061/dryad.ms1fm8p
title: Data from: Wind-associated detours promote seasonal migratory connectivity in a flapping flying long-distance avian migrant

description: 1. It is essential to gain knowledge about the causes and extent of
 migratory connectivity between stationary periods of migrants to further
 the understanding of processes affecting populations, and to allow
 efficient implementation of conservation efforts throughout the annual
 cycle. Avian migrants likely use optimal routes with respect to mode of
 locomotion, orientation and migration strategy, influenced by external
 factors such as wind and topography. In self-powered flapping flying birds
 any increases in fuel loads are associated with added flight costs.
 Energy-minimizing migrants are therefore predicted to trade-off extended
 detours against reduced travel across ecological barriers with no or
 limited foraging opportunities. 2. Here we quantify the extent of detours
 taken by different populations of European nightjars Caprimulgus
 europaeus, to test our predictions that they used routes beneficial
 according to energetic principles and evaluate the effect of route shape
 on seasonal migratory connectivity. 3. We combined data on birds tracked
 from breeding sites along a longitudinal gradient from England to Sweden.
 We analysed the migratory connectivity between breeding and main
 non-breeding sites, and en route stopover sites just south of the Sahara
 desert. We quantified each track’s route extension relative to the direct
 route between breeding and wintering sites, respectively, and contrasted
 it to the potential detour derived from the barrier reduction along the
 track while accounting for potential wind effects. 4. Nightjars extended
 their tracks from the direct route between breeding and main non-breeding
 sites as they crossed the Mediterranean Sea – Sahara desert, the major
 ecological barrier in the Palaearctic-African migration system. These
 clockwise detours were small for birds from eastern sites but increased
 from east to west breeding longitude. Routes of the tracked birds were
 associated with partial reduction of the barrier-crossing resulting in a
 trade-off between route extension and barrier reduction, as expected in an
 energy-minimizing migrant. 5. This study demonstrates how the costs of
 barrier crossings in prevailing winds can disrupt migratory routes towards
 slightly different goals, and thereby promote migratory connectivity. This
 is an important link between individual migration strategies in
 association with an ecological barrier, and both spatially and demographic
 population patterns.
description: Stationary
 locationsThis table contains
 stationary locations for birds included in the study. The columns contain
 information regarding: Id: Individual identifier, Stationary period:
 breeding/stopover/wintering sites (note that "Long_stop"
 corresponds to locations where only the longitude is known), Latitude,
 Longitude, Region; identifies the three main regions containing the
 location, country and breeding location of the bird, Barrier; if the stop
 is prior a barrier, and Season (autumn/spring).Raw data
 simulationsThis table contains raw
 data for the presented route simulations. The columns describe the season
 (autumn/spring) location (Lat, Lon), datetime of wind extraction, ground
 speed at different pressure levels and maximum speed at each
 location.