Variations in movement and habitat selection by Eurasian curlew at two important sites in Europe throughout winter
Data files
Aug 19, 2026 version files 754.45 MB
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Database_France_wintering_curlew.csv
492.19 MB
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Database_Germany_wintering_curlew.csv
261.64 MB
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Habitat_use_Pertuis_Wadden_Sea.csv
610.51 KB
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README.md
12.44 KB
Abstract
Shorebirds aim to replenish their body reserves during the wintering season to ensure their subsequent survival and to improve their breeding performance. However, their space use depends on their fluctuating resource availability and energy requirements throughout the winter. Hence, this study aimed to determine if the space and habitats used by Eurasian curlews (Numenius arquata) were influenced by their wintering site and stage. Sixty-two curlews were equipped with GPS tags at two major wintering sites in Europe with contrasting waterbird density: the Pertuis Charentais in France and the German part of the Wadden Sea. Their home ranges (HRs) and foraging habitat selection were compared according to three wintering stages requiring different energy demands (i.e., early winter, mid-winter, and late winter before migration). Curlews exhibited similar HR sizes at both sites throughout the winter, suggesting no effect of waterbird density on individuals’ space use. HR sizes were larger during the day than at night and showed high inter-individual variability, unrelated to sex. Notably, the HRs were larger during the first winter stage (i.e., Arrival–September), with curlews spending a greater proportion of time on mudflats, and selecting distinct foraging areas located further from the coast at this stage. Curlews in the WS fed mainly on the mudflats, while curlews in the PC fed on the mudflats, but also on biogenic reefs, oyster parks, and seagrass beds, the latter being favoured during the first stage. These results suggest the need for greater consideration of the distribution of curlews and other shorebirds at the beginning of the wintering season to define areas and habitats of importance to support future management and conservation measures. Indeed, birds are particularly prone to disturbance during the first winter stage, when tourism pressure on the coast is high and birds tend to be more mobile.
Dataset DOI: 10.5061/dryad.nvx0k6f6j
Description of the data and file structure
Introductory information
Database_Germany_wintering_curlew
- Excel spreadsheet of data collected from Ecotone Skua and Ornitela GPS tags
- Data collected by the University of Kiel, Forschungs- und Technologiezentrum Westküste (FTZ)
- Address: Hafentörn 1, 25761 Büsum, Germany
- Principal investigator: Philipp Schwemmer
- Co-investigators: Stefan Garthe
- Tag data collected from 2014 to 2024
- GPS tags were attached to birds in Schleswig-Holstein and Lower Saxony, Germany
- File was created in June 2025
Database_France_wintering_curlew
- Excel spreadsheet of data collected from Ecotone Sterna and Ornitela GPS tags
- Data collected by La Rochelle University, National Museum of National History and National Nature Reserve of Moëze-Oléron.
- Address: Laboratory Littoral Environnement et Sociétés UMR LIENSs at La Rochelle University, 2 Rue Olympe de Gouges, 17000 La Rochelle, France
- Address: CESCO, UMR7204 MNHN‐CNRS‐Sorbonne University, 43 rue Buffon, 75005 Paris, France
- Address: National Nature Reserve of Moëze-Oléron, LPO Ligue pour la Protection des Oiseaux, Plaisance, 17780 Saint-Froult, France
- Principal investigator: Pierrick Bocher
- Co-investigators: Frédéric Jiguet
- Associate investigators: Pierre Rousseau
- Tag data collected from 2016 to 2024
- GPS tags were attached to birds in Saint-Froult, France
- File was created in June 2025
Methodological information
We tagged 62 adult wintering Eurasian curlews (30 males, 30 females, 2 unknown sex), either in the German part of the Wadden Sea between 2014 and 2024 (27 individuals) or in the Pertuis Charentais in France between 2016 and 2024 (35 individuals). We caught curlews using mist nets placed on high-tide roosts during new moon nights. We equipped individuals with GPS-GSM solar tags provided by two manufacturers: we equipped 10 individuals with Ecotone tags, Poland (Skua (17g), Sterna (7.5g)) and 52 individuals with Ornitela tags, Lithuania (OT-10 (10g), OT-15 (15g), OT-20 (20g), OT-E10 (12g)). All tags weighted less than 3% of the birds body mass (Phillips et al. 2003). We fitted the tags in Germany with the "wing-loop" method (Guillaumet et al. 2011) with Teflon harnesses and in France using the "leg-loop" method (Mallory and Gilbert, 2008) with harnesses made of silicone analytical tubes.
Files and variables
File: Habitat_use_Pertuis_Wadden_Sea.csv
Description: A table containing the proportion of each habitat within the resting (i.e., when birds were resting 3 h before and after high tide) and foraging (i.e., when birds where foraging 3 h before and after low tide) home ranges and core areas of curlews wintering in the Pertuis Charentais (PC) in France and in the German part of the Wadden Sea (WS).
The file is semicolon-delimited.
The individual utilization distribution (UD), i.e., the probability density that an animal was present in a given area, was used to highlight the space used by individuals. UDs were calculated using the kernel density estimation method (KDE) with the ‘kernelUD’ function of the ‘adehabitatHR’ package. The cell size was adjusted to 20 m to consider the minimum precision of 10 m of the GPS tags. An 80-m smoothing was used for all individuals, which is considered as the best compromise between under- and over-smoothing. An Albers equal-area projection adjusted to the extent of wintering GPS fixes was used to project the HRs.
Individual home ranges (95% KDE) and core areas (50% KDE) were calculated based on GPS fixes considered as either foraging or resting positions for each wintering stage (i.e., early winter (Arrival-Sep), middle winter (Oct-Jan), last winter (Feb-Departure)). Only individuals with ≥1,000 GPS fixes recorded from a minimum of four satellites to increase spatial accuracy were selected. A total of 62 individuals were used with 27 individuals used throughout the three winter stages (Arr–Sep n=42; Oct–Jan n=44; Feb–Dep n=48).
The CORINE Land Cover (CLC) data from 2018 were used to similarly describe the habitats with a minimum area of 25 ha in France and 5 ha in Germany. These databases allowed the delineation of three coastal habitat categories: ‘bare mudflats’ (CLC code: 423) with estuaries and rivers also considered as mudflats at low tide (codes: 511, 522), ‘sandbanks’ (code: 331), and marshes (code: 421). Marshes were considered as ‘saltmarshes’ in the WS, i.e., marshes periodically flooded by seawater, and as ‘marshes’ in the PC, corresponding to basins into which seawater is artificially fed. Site-specific habitat layers were also employed to describe the typology of the coastal and intertidal habitats particularly used by curlews in more detail. Hence, ‘seagrass beds’, ‘oyster parks’, ‘biogenic reefs’ resulting from former oyster parks and ‘rocky shores’ were delineated in the PC using a portable GPS for the first two habitats, and manually using satellite imagery for the last two habitats. Coastal and intertidal habitat layers of the WS were collected using Mendeley Data http://dx.doi.org/10.17632/2rvtxpjtfg.1 (Baptist et al. 2019), allowing the delineation of ‘seagrass beds’ and to adjust the delineation of ‘saltmarshes’ and ‘sandbanks’ (i.e., coarse sand with a median grain size of 250–2,000 μm and a silt percentage <25%).
Variables
- Individual: Bird ID
- Habitat: Arable lands (1), Agricultural grasslands (2), Natural grasslands (3), Saltmarshes (4), Marshes (5), Seagrass beds (6), Bare mudflats (7), Sandbanks (8), Rocky shores (9), Oyster parks (10), Biogenic reefs (11), Other habitats (forests, buildings) (12), Water bodies (13)
- Area: habitat area within the home range (ha)
- Area_total: Total area of the home range (ha)
- Kernel: Home Range (HR) or Core Area (CA)
- Period: Winter stage. Early winter (Arrival-Sep), middle winter (Oct-Jan), last winter (Feb-Dep).
- Country: France or Germany (Wadden Sea)
- Activity: Foraging (i.e., when birds where foraging 3 h before and after low tide) or Resting (i.e., when birds were resting 3 h before and after high tide)
- Site: Specific wintering site within the Pertuis Charentais (France) and the Wadden Sea (Germany)
File: Database_Germany_wintering_curlew.csv
Description: A database with all the GPS fixes of curlews wintering in the Wadden Sea (Germany). Missing data is referred as 'NA'.
Variables
- Bird.ID: Bird identifier.
- Country.Tagged: Country where the bird was tagged.
- Season: Year of each GPS fix.
- Activity: Only wintering season.
- Date.Time: Datetime of each GPS fix.
- Distance.from.Site: Distance from the first roost (km). The approximate start of the wintering season was defined when the bird reached one of the two study sites and stayed there >20 days. Then, the position of the first wintering roost used at the beginning of the season was determined by isolating the GPS fixes obtained during the first 3 days of the wintering season for each individual and displaying them on a 0.0001° × 0.0001° grid covering the range of latitudes and longitudes visited by each individual during these days. The centre of the cell with the largest number of GPS fixes was defined as the first roost. The corrected start and end of the wintering season were defined as the times when birds arrived at <20 km from their first wintering roost and moved >20 km away for the first time to start their spring migration, respectively.
- Site.Latitude: Latitude of the first roost.
- Site.Longitude: Longitude of the first roost.
- Latitude: Latitude of each GPS fix.
- Longitude: Longitude of each GPS fix.
- Breeding.Country: Breeding country.
- Wintering.Country: Wintering country.
- Age: Only adults (A).
- Gender: Males (M), Females (F).
- Sensor: Only Global Positioning System (GPS).
- Speed: Flight speed (kilometer/hour).
- Altitude: Flight altitude (meters). Height above mean sea level.
- Temperature: External temperature (°Celsius)
- Acceleration.X: Instant acceleration (X axis).
- Acceleration.Y: Instant acceleration (Y axis).
- Acceleration.Z: Instant acceleration (Z axis).
- Mag.X: Magnetic field strength (X axis)
- Mag.Y: Magnetic field strength (Y axis)
- Mag.Z: Magnetic field strength (Z axis)
- Satcount: Number of satellites whose signals are picked up by the GPS to define the position.
- Wintering.Season: Curlews regularly reach their wintering site in early summer (early June to late July) and leave in early spring (early March to late April) to reach their breeding grounds from northern Europe to the Arctic Circle. The wintering season thus corresponds to the year when the bird is supposed to arrive on the site - the year when the bird id supposed to leave. For example, January 2020 corresponds to the wintering season 2019-2020.
- Bird.ID_Season.x / Bird.ID_Season.y : Bird identifier and first year of the wintering season.
- Wintering.event: Number of the recorded wintering seasons of each individual.
- Bird.ID_Wintering.Season: Bird identifier and wintering event.
- New_time_interval: Time interval between each GPS fix.
- DateTimeLocal: Local datetime according to the country.
- Month: Month of each GPS fix.
- Wintering.site: the area was divided into 1 wintering site in the Pertuis Charentais (i.e., Marennes-Oléron Bay) and 3 in the German part of the Wadden Sea (i.e., the coasts of Nordfriesland as well as the coasts of Dithmarschen districts in the federal state of Schleswig-Holstein and the coasts of the Cuxhaven and Wesermarsh districts in Lower Saxony). Some individuals moved between different sites throughout the wintering season. The first and subsequent sites used by each individual were distinguished in this column.
- Keep.for.aug.oct.analyses: Indicate if the bird was kept for early winter analyses.
- Keep.for.feb.mar.analyses: Indicate if the bird was kept for middle winter analyses.
- Keep.for.nov.jan.analyses: Indicate if the bird was kept for late winter analyses.
- Date: Date from the Date.Time column.
- Time: Time from the Date.Time column.
- ID_day_night: Day (between sunrise and sunset) or Night (between sunset and sunrise).
- Hrise: Sunrise datetime defined with the 'suncalc' R package.
- Hset: Sunset datetime defined with the 'suncalc' R package.
- First.year.wintering.event: First year of the wintering season. For example, if the wintering season was 2019-2020, the first year wintering event was 2019.
- Keep.for.study: Indicate if the bird was kept for the study.
- Keep.for.arriving.sept.analyses: Indicate if the bird was kept for arrival-September analyses.
- Keep.for.oct.jan.analyses: Indicate if the bird was kept for October-January analyses.
- Keep.for.feb.departure.analyses: Indicate if the bird was kept for February-departure analyses.
- Period: AS (Arrival-September), OJ (October-January), FD (February-Departure).
- Site: Specific position of individuals.
- HT_time: High tide time
- HT_height: High tide height (meters)
- HT_timespan.h: Timespan in hours between local and high tide time.
- LT_time: Low tide time
- LT_timespan.h: Timespan in hours between local and low tide time.
- Water_level: Water level (meters) at each GPS fix.
File: Database_France_wintering_curlew.csv
Description: A database with all the GPS fixes of curlews wintering in the Pertuis Charentais (France). Missing data is referred as 'NA'.
Variables
The variables are the same as for 'Database_Germany_wintering_curlew.csv' file.
Code/software
All statistical analyses were performed using R software (version 4.4.1, R Core Team 2024).
Access information
Data were deposited on the Movebank platform (www.movebank.org) under the Movebank ID 74810223 (Germany) and 1077731101 and 325569416 (France).