Cranes soar on thermal updrafts behind cold fronts as they migrate across the sea
Data files
Feb 08, 2024 version files 2.10 GB
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16113_1HzGPS_and_ACC_annotated.csv
2.71 MB
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16115_1HzGPS_and_ACC_annotated.csv
20.28 MB
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16116_1HzGPS_and_ACC_annotated.csv
2.73 MB
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17051_1HzGPS_and_ACC_annotated.csv
110.42 MB
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17053_1HzGPS_and_ACC_annotated.csv
11.29 MB
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17054_1HzGPS_and_ACC_annotated.csv
97.53 MB
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17055_1HzGPS_and_ACC_annotated.csv
124.85 MB
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17059_1HzGPS_and_ACC_annotated.csv
35.59 MB
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17076_1HzGPS_and_ACC_annotated.csv
155.51 MB
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17077_1HzGPS_and_ACC_annotated.csv
19.31 MB
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17079_1HzGPS_and_ACC_annotated.csv
150.42 MB
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17080_1HzGPS_and_ACC_annotated.csv
61.77 MB
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17081_1HzGPS_and_ACC_annotated.csv
106.49 MB
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17082_1HzGPS_and_ACC_annotated.csv
70.99 MB
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17083_1HzGPS_and_ACC_annotated.csv
13.17 MB
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17086_1HzGPS_and_ACC_annotated.csv
111.43 MB
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17087_1HzGPS_and_ACC_annotated.csv
45.41 MB
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17088_1HzGPS_and_ACC_annotated.csv
20.19 MB
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17089_1HzGPS_and_ACC_annotated.csv
269.13 MB
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17093_1HzGPS_and_ACC_annotated.csv
128.48 MB
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17095_1HzGPS_and_ACC_annotated.csv
27.47 MB
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17096_1HzGPS_and_ACC_annotated.csv
65.70 MB
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17099_1HzGPS_and_ACC_annotated.csv
70.02 MB
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17100_1HzGPS_and_ACC_annotated.csv
27.22 MB
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17102_1HzGPS_and_ACC_annotated.csv
63.97 MB
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17103_1HzGPS_and_ACC_annotated.csv
58.45 MB
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17104_1HzGPS_and_ACC_annotated.csv
1.03 MB
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17105_1HzGPS_and_ACC_annotated.csv
25.35 MB
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181949_1HzGPS_and_ACC_annotated.csv
66.09 MB
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181950_1HzGPS_and_ACC_annotated.csv
61 MB
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181951_1HzGPS_and_ACC_annotated.csv
48.92 MB
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181952_1HzGPS_and_ACC_annotated.csv
20.40 MB
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AnnotatedTimePointsMedSea.csv
279.38 KB
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README.md
13.33 KB
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SoarGlide.csv
1.68 MB
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TheramlStats.csv
2.85 MB
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TimesOfMigrationFall.csv
5.37 KB
Abstract
Thermal soaring conditions above the sea have long been assumed absent or too weak for terrestrial migrating birds, forcing large obligate soarers to take long detours and avoid sea crossing, and facultative soarers to cross exclusively by costly flapping flight. Thus, while atmospheric convection does develop at sea and is utilized by some seabirds, it has been largely ignored in avian migration research. Here we provide direct evidence for routine thermal soaring over open sea in the common crane, the heaviest facultative soarer known among terrestrial migrating birds. Using high-resolution biologging from 44 cranes tracked across their transcontinental migration over 4 years, we show that soaring characteristics and performance were no different over sea than over land in mid-latitudes. Sea-soaring occurred predominantly in autumn when large water-air temperature difference followed mid-latitude cyclones. Our findings challenge a fundamental paradigm in avian migration research and suggest that large soaring migrants avoid sea crossing not due to absence or weakness of thermals but due to their uncertainty and the costs of prolonged flapping. Marine cold air outbreaks, imperative to the global energy budget and climate system, may also be important for bird migration, calling for more multidisciplinary research across biological and atmospheric sciences.
README: Cranes soar on thermal updrafts behind cold fronts as they migrate across the sea
https://doi.org/10.5061/dryad.t76hdr871
This dataset and accompanying R scripts pertain to the research study on crane migration above the sea. The focus of this study is to analyze the migratory patterns of cranes, particularly their utilization of thermal updrafts and soaring-gliding dynamics during sea crossing. The dataset includes high-resolution GPS and accelerometer data, annotated with environmental variables, and the R scripts are tailored for statistical analysis and visualization of these data.
Description of the data and file structure
The data folder contains the following files:
1HzGPS_and_ACC_annotated (multiple files):
- 1Hz data for individual cranes, annotated with environmental variables.
- File names include individual crane IDs.
ThermalStats.csv:
- Summarizes 10-minute segments with and without thermal activity.
- Used in
ThermalSections_analysis&plot.Randtime_scales_analysis.R.
SoarGlide.csv:
- Contains data on coupled soaring-gliding events.
- Used in
soaring&gliding_plot&analyse.R.
AnnotatedTimePointsMedSea.csv:
- Data for annotated time scale data for Mediterranean sea crossing.
- Used in
time_scales_analysis.R.
TimesOfMigrationFall.csv:
- Number of days crane stayed at the last stopover site before crossing the Mediterranean sea
- Used in
time_scales_analysis.R.
Code/Software
The code folder includes R scripts designed for the statistical analysis high-resolution datasets:
ThermalSections_analysis&plot.R:
- Performs statistical analysis of 10-minute thermal sections.
- Generates Figure 2B.
soaring&gliding_plot&analyse.R:
- Analyzes coupled soaring-gliding events.
- Generates Figure 3A.
time_scales_analysis.R:
- Conducts time-scale analysis.
- Generates Figure 4A.
Metadata Description
(1) Data 1HzGPS_and_ACC_annotated Tables:
NAN indicates not available.
- Tag: Identifier for the tracked animal
- TimeCont: timestamps of observations (UTC).
- Latitude: Geographic latitude where the observation was recorded.
- Longitude: Geographic longitude where the observation was recorded.
- Altitude_m: Altitude of the crane (m).
- Speed_km_h: Speed of the crane (km/h).
- direction_deg: Direction of crane movement (degrees clockwise from north).
- OverSeaOrLand: Indicator of whether the crane is over the sea or land during observation (0=land, 1=Black sea, 2=Mediterranean sea).
- mag_x, mag_y, mag_z: Components of the magnetic field measurement in the x, y, and z directions.
- acc_x, acc_y, acc_z: Accelerometer readings in the x, y, and z directions (m^2/sec).
- Interpolated_Lat: Interpolated latitude values.
- Interpolated_Lon: Interpolated longitude
- InterpolatedElevation: Interpolated elevation values (m).
- running_Flap_rate: estimated flap rate form 1Hz data based on a calibration dataset of 10Hz (flaps per second)
- AleAboveTerrain: Altitude of the crane above the terrain (m).
- TerrainHeight: Height of the terrain above sea level (m).
- quartile: Statistical quartile information.
- Individual: tag number used for environmental annotation.
- t2m: Temperature at 2 meters above surface level (°C).
- sst: Sea surface in C temperature (°C).
- blh: Boundary layer height (m).
- cbh: Cloud base height (m).
- cape: Convective available potential energy (J/kg).
- cin: Convective inhibition (J/kg).
- msshf: Mean sea sensible heat flux (W/m^2).
- tcc: Total cloud cover (%).
- msl: Mean sea level pressure (Pa).
- u850, u925: Zonal wind component at 850 hPa and 925 hPa pressure levels.
- v850, v925: Meridional wind component at 850 hPa and 925 hPa pressure levels.
- t850, t925: Temperature at 850 hPa and 925 hPa pressure levels.
- sstDiff: Difference between sea and air temeperature (°C)
- windDirection850, windDirection925: Wind direction at 850 hPa and 925 hPa pressure levels.
- windSpeed850, windSpeed925: Wind speed at 850 hPa and 925 hPa pressure levels.
(2) ThermalStats:
NAN indicates not available.
- Individual: Identifier for the tracked animal.
- UniqueSectionCounter: Sequential counter for a distinct 1 Hz GPS burst (min10 min., but can be longer).
- Date: Date and time of observation (DD-MMM-YYYY HH:MM:SS).
- lat_start: Geographic latitude at the start of a 10 minutes segment (Degrees).
- lon_start: Geographic longitude at the start of a 10 minutes segment (Degrees).
- OverSea: Flag indicating whether the segment is over the sea (0=land, 1=Black sea, 2=Mediterranean sea).
- day_time: Flag indicating it during daytime or during nighttime (0=night, 1=day).
- time_since_sunrise_h: Time since sunrise at the start of the segment (Hours).
- time_since_sunset_h: Time since sunset at the start of the segment (Hours).
- time_of_part_min: Duration of the observed segment (Minutes).
- TotalDistance: Total distance covered in the segment (meters).
- vg: Ground speed during the segment (m/sec).
- va: Airspeed during the segment (m/sec).
- tw: Tailwind component during the segment (m/sec).
- sw: Sidewind component during the segment (m/sec).
- meanFlapRate: Average flap rate of the individual during the segment (Flaps/sec).
- percent_time_in_thermals: Percentage of the segment time spent in thermals (%).
- time_in_thermals_sec: Total time spent in thermals during the segment (Seconds).
- mean_thermal_length_sec: Average duration of thermal events during the segment (Seconds).
- mean_climb_rate: Average climb rate during thermal events (m/s).
- mean_max_elevation_above_ground: Average maximum elevation above ground level for each thermal during the segment (Meters).
- Mean_blh: Mean boundary layer height during the segment (Meters).
- Mean_msl: Mean sea level pressure during the segment (Pa).
- Mean_DeltaT: Mean temperature difference during the segment (Degrees Celsius).
- wvel: Wind velocity during the segment (m/s).
- wang: Wind angle during the segment (Degrees).
- number_of_thermals: Number of thermal events encountered during the segment.
- age: Categorical age of the individual (1= Breeding adult, 2 = Adult with unknown breeding status, 3 = Subadult, 4 = Juvenile).
- age_w: Age class of the individual.
- sex: Sex of the individual (e.g., Male, Female, Unknown).
(3) SoarGlide:
NAN indicates not available.
- individual: Identifier for the tracked animal.
- datetime_start: Date and time when the soaring-gliding segment started (DD-MMM-YYYY HH:MM:SS).
- lon_start: Geographic longitude at the start of the observation (Degrees).
- lat_start: Geographic latitude at the start of the observation (Degrees).
- time_soaring_sec: Total time spent soaring during soaring-gliding segment (Seconds).
- climb_rate_m_sec: Average climb rate while soaring (m/s).
- falp_rate_climb: Flap rate during the climb phase (Flaps/sec).
- falp_prop_climb: Proportion of time flapping during the climb phase (%).
- type_thermal: Type of thermal encountered (1 = classic soaring, 2 = spring-like soaring pattern).
- start_alt_above_terr: Starting altitude above terrain at the beginning of the soaring phase (Meters).
- exit_alt_above_terr: Exit altitude above terrain at the end of the soaring phase (Meters).
- time_gliding_sec: Total time spent gliding during the soaring-gliding segment (Seconds).
- distance_gliding_m: Total distance covered while gliding (Meters).
- sink_speed_m_sec: Average sink speed while gliding (m/s).
- air_speed_m_sec: Airspeed during the gliding phase (m/s).
- air_speed_calc_m_sec: airspeed during the gliding phase based on tailwind estimated from thermal drift (m/s).
- tail_wind: tailwind during the gliding phase (m/s).
- tail_wind_calc: estimated tailwind using bird drift in thermals from the horizontal displacement of thermals (m/s).
- side_wind: sidewind during the gliding phase (m/s).
- side_wind_calc: estimated sidewind using bird drift in thermals from the horizontal displacement of thermals (m/s).
- falp_rate_glide: Flap rate during the gliding phase (Flaps/sec).
- falp_prop_glide: Proportion of time flapping during the gliding phase (%).
- mean_blh: Mean boundary layer height during the observation period (Meters).
- sea_land: Indicator of whether the soaring-gliding segment (0=land, 1=Black sea, 2=Mediterranean sea)..
- day_time: Indicator of whether the soaring-gliding segment was during daytime or nighttime (0=night, 1=day).
- age: Categorical age of the individual (1= Breeding adult, 2 = Adult with unknown breeding status, 3 = Subadult, 4 = Juvenile).
- age_w: Age class of the individual.
- sex: Sex of the individual (Male, Female, Unknown).
- Vopt: Optimal flight speed which maximizes bird cross-country speed (m/s).
- RAFI: Risk-Averse Flight Index.
- RAFIcalc: Risk-Averse Flight Index calculated based on estimated tailwind.
- Date: Date of the soaring-gliding segment (DD-MMM-YY).
(4) AnnotatedTimePointsMedSea:
NAN indicates not available.
- indev: Identifier for the tracked animal.
- Date: Date of the real sea crossing event (YYYY-MM-DD).
- fall: Flag indicating whether the season of the sea crossing event (0 = spring, 1 = fall).
- thermap_presence: Indicator of thermal presence during the observation (0 = no thermal soring during crossing, 1 = at lest 1 thermal soaring event).
- daysBack: Number of timescales relative to the autumn real sea crossing event.
- lat: Geographic latitude used for annotation (Degrees).
- lon: Geographic longitude used for annotation (Degrees).
- mig_ang: Migration angle at the time of observation (Degrees).
- datetime_utc: Date and time at the location (DD-MMM-YYYY HH:MM:SS).
- datetime: Date and time UTC used for annotation (DD-MMM-YYYY HH:MM:SS).
- t2m: Temperature at 2 meters above the surface (Degrees Celsius).
- sst: Sea surface temperature (Degrees Celsius).
- blh: Boundary layer height (Meters).
- cbh: Cloud base height (Meters).
- cape: Convective Available Potential Energy (Joules per kilogram).
- cin: Convective Inhibition (Joules per kilogram).
- msshf: Mean Sea Surface Heat Flux (Watts per square meter).
- tcc: Total Cloud Cover (fraction from 0 to 1).
- msl: Mean Sea Level Pressure (Pascals).
- u850: Zonal wind component at 850 hPa (Meters per second).
- u925: Zonal wind component at 925 hPa (Meters per second).
- v850: Meridional wind component at 850 hPa (Meters per second).
- v925: Meridional wind component at 925 hPa (Meters per second).
- t850: Temperature at 850 hPa (Degrees Celsius).
- t925: Temperature at 925 hPa (Degrees Celsius).
- sstdiff: Difference between sst and t2m (Degrees Celsius).
- windDir850: Wind direction at 850 hPa (Degrees).
- windSpeed850: Wind speed at 850 hPa (Meters per second).
- windDir925: Wind direction at 925 hPa (Degrees).
- windSpeed925: Wind speed at 925 hPa (Meters per second).
- GPCC: Precipitation (Millimeters).
- time_point: location during the crossing used for annotation, "sea enter" was used for the analysis (1 = starting point, 2 = sea enter 3 =in sea).
- tw: Tailwind component (Meters per second).
- sw: Sidewind component (Meters per second).
(5) TimesOfMigrationFall:
NAN indicates not available.
- indev: Identifier for the tracked animal.
- Date: Date of the sea crossing event (YYYY-MM-DD).
- fall: Flag indicating season (0 = spring, 1 = fall).
- Hz1_section_num: number of 10 minutes 1Hz sections during the sea crossing event.
- mean_thermal_prop: Mean proportion of time spent in thermals during the sea crossing event.
- prop_section_with_thermal: Proportion of 10 minutes sections containing thermal soaring during the sea crossing event.
- thermals: Number of thermal events encountered during the sea crossing event.
- lat_start_migration: Geographic latitude at the start of the sea crossing event (Degrees).
- lon_start_migration: Geographic longitude at the start of the sea crossing event (Degrees).
- datetime_start_migration_utc: Date and time at the start of the sea crossing event in UTC (DD-MMM-YYYY HH:MM:SS).
- datetime_enter_sea_utc: Date and time when the individual enters the sea area in UTC (DD-MMM-YYYY HH:MM:SS).
- datetime_exit_sea_utc: Date and time when the individual exits the sea area in UTC (DD-MMM-YYYY HH:MM:SS).
- time_at_sea: Total time spent at sea during the sea crossing event (Hours).
- Days_at_stopover: Number of days spent at the last stopover site before the sea crossing event.
- ang: Angle of movement at the beginning of the sea crossing event (Degrees).