DOI: 10.5061/dryad.zgmsbccqz
title: Data from: Causes of differential migration distance: Test of seven mechanistic hypotheses in an arctic raptor

description: Exploring the causes of differential migration, or variation in migration
 distance, has increased our understanding of the remarkable variation in
 migratory behavior exhibited by birds more generally. However,
 considerable uncertainty exists regarding the mechanisms underlying
 differential migration distance in birds, despite it being a common
 phenomenon. We leveraged migration distances from GPS-tracked rough-legged
 hawk, Buteo lagopus, to test predictions deduced from seven
 hypotheses proposed to explain the underlying cause(s) of differential
 migration distance. We provide the first empirical evidence in support of
 a social dominance food maximization hypothesis whereby dominant
 individuals migrate to higher quality nonbreeding locations with respect
 to foraging efficiency regardless of migration distance. Within females,
 larger, more dominant individuals migrated intermediate distances while
 smaller, subordinate individuals migrated both longer and shorter
 distances. We also found support for the social dominance distance
 minimization hypothesis because more aggressive females migrated shorter
 distances, although increased aggression at shorter distances may be a
 consequence of poor body condition. Within males, we found some support
 for the fasting endurance and thermal tolerance hypotheses because body
 size was negatively correlated with migration distance. Body size was also
 negatively correlated with food availability and winter minimum
 temperatures within both sexes, providing additional mechanistic support
 for the fasting endurance and thermal tolerance hypotheses. Overall, our
 results suggest that differential migration distance within rough-legged
 hawks is caused by a combination of competition for nonbreeding resources
 and constraints on fasting endurance or thermal tolerance, but is
 unrelated to competition for breeding opportunities, dietary preferences,
 or flight efficiency.
description: # Causes of differential migration distance: Test of seven mechanistic
 hypotheses in an arctic raptor Dataset DOI:
 [10.5061/dryad.zgmsbccqz](10.5061/dryad.zgmsbccqz) ## Description of the
 data and file structure We leveraged migration distances from GPS-tracked
 rough-legged hawks, *Buteo lagopus,* to test predictions deduced from
 seven hypotheses proposed to explain the underlying cause(s) of
 differential migration distance. ### Files and variables #### File:
 2024-09-19_RLHA_Differential-Migration.csv **Description:** see R scripts
 for use. 'NA' cells refers to missing data (either missing or
 not included because not applicable to the analyses). ##### Variables *
 tagid: bird ID number * season: migration season * sex: sex of the bird *
 agemigr: minimum age at time of migration * age3: age class (1-4),
 detailed in methods. * winterday: winter day of capture * migrdistance:
 migration distance (km) * dist_pred: Was migration distance predicted
 (inferred)? Y/N * dist_remove: Should distance be removed from analysis? Y
 * breedlat: breeding latitude * breedlong: breeding longitude * mass: bird
 mass (g) * hwi: bird hand-wing index * preysize_BT: average mass of prey
 taxa from DNA metabarcoding  * breadth_BT: prey species richness from DNA
 metabarcoding  * num_bites: aggressiveness, number of bites. #### File:
 Aggressiveness_2024-11-19.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables * Band:
 bird band number * tagid: bird transmitter number * winterday: winter day
 of capture * sex: bird sex * mass: bird mass at capture (g) * keel_mm:
 body condition index at capture based on measurement of breast muscle
 depth (mm) * num_bites: aggressiveness, number of bites. #### File:
 2024-09-25_RLHA_Differential-Migration.csv **Description:** see R scripts
 for use. 'NA' cells refers to missing data (either missing or
 not included because not applicable to the analyses). ##### Variables *
 tagid: bird transmitter number * season: migration season * sex: bird sex
 * age3: age class (1-4), see manuscript methods for details * winterdayCO:
 winter day of capture for carry-over effects * migrdistance: migration
 distance (km) * dist_pred: was distance predicted (inferred)? * breedlat:
 breeding latitude * breedlong: breeding longitude * keel_mm: body
 condition index at capture based on measurement of breast muscle depth
 (mm) * hapto: haptoglobin levels * agglut: agglutination titers #### File:
 2025-02-19_RLHA_1mig-Differential-Migration.csv **Description:** see R
 scripts for use. 'NA' cells refers to missing data (either
 missing or not included because not applicable to the analyses). #####
 Variables * tagid: bird transmitter ID * year: migration year * season:
 migration season * sex: bird sex * agemigr: minimum age in cycles at time
 of migration * age3: age class (1-4) at time of migration, see manuscript
 methods * winterday: winter day of capture * migrdistance: migration
 distance (km) * dist_remove: Should distance be removed from analysis? *
 breedlat: breeding latitude * breedlong: breeding longitude * mass: bird
 mass (g) at capture #### File: 2024-03-26_Fall-Migr-snow-temp.csv
 **Description:** see R scripts for use. 'NA' cells refers to
 missing data (either missing or not included because not applicable to the
 analyses). ##### Variables * tagid: bird transmitter ID * year: migration
 year * season: migration season * sex: bird sex * begDate: winter begin
 date * endDate: winter end date * migrdistance: migration distance (km) *
 longbreedlat: breeding latitude * longbreedlong: breeding longitude *
 mass: bird body mass (g) at capture #### File:
 2025-02-14_RLHA_Differential-Migration.csv **Description:** see R scripts
 for use. 'NA' cells refers to missing data (either missing or
 not included because not applicable to the analyses). ##### Variables *
 tagid: bird transmitter ID * season: migration season * sex: bird sex *
 agemigr: minimum age in cycles at time of migration * age3: age class
 (1-4) at time of migration, see manuscript methods * migrdistance:
 migration distance (km) * breedlat: breeding latitude * breedlong:
 breeding longitude * FPT: first passage time (day of year since 1-Jan) *
 mass: bird body mass (g) at capture #### File: Conway-GPS_snow-cover.csv
 **Description:** see R scripts for use. 'NA' cells refers to
 missing data (either missing or not included because not applicable to the
 analyses). ##### Variables * timestamp: bird GPS date/time position *
 location-long: bird longitude at timestamp * location-lat: bird latitude
 at timestamp * sensor-type: GPS sensor type * individual-local-identifier:
 bird transmittermanuscriptNARR SFC Snow Cover at Surface: proportion snow
 cover via movebank ENVI (see manusript methods). #### File:
 Conway-GPS_snow-depth.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables *
 timestamp: bird GPS date/time position * location-long: bird longitude at
 timestamp * location-lat: bird latitude at timestamp * sensor-type: GPS
 sensor type * individual-local-identifier: bird transmitter ID * NCEP NARR
 SFC Snow Depth at Surface:  snow depth via movebank ENVI (see manuscript
 methods). #### File: WingLoading_Corrected_HWI.csv **Description:** see R
 scripts for use. 'NA' cells refers to missing data (either
 missing or not included because not applicable to the analyses). #####
 Variables * ID: row identifier * tagid: bird transmitter ID * mass: bird
 body mass (g) at capture * AspectRatio_uc: uncorrected aspect ratio *
 AspectRatio_c1: partially corrected aspect ratio * AspectRatio_c2: full
 corrected aspect ratio * wing_loading_uc: uncorrected wing loading *
 wing_loading_c1: partially corrected wing loading * wing_loading_c2: full
 corrected wing loading * hwi: hand-wing index #### File:
 Kidd-Argos_snow-temp.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables *
 timestamp: bird GPS date/time position * location-long: bird longitude at
 timestamp * location-lat: bird latitude at timestamp * argos:lc: argos
 location class * sensor-type: GPS sensor type *
 individual-local-identifier: bird transmittermanuscriptNARR SFC Snow Cover
 at Surface: proportion snow cover via movebank ENVI (see
 manusrmanuscriptds). * NCEP NARR SFC Temperature at Surface: temperature
 via movebank ENVI (see manuscript). * NCEP NARR SFC Snow Depth at
 Surface:  snow depth via movebank ENVI (see manusript methods). #### File:
 rlha_snow-temp-data-final2.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables *
 identity: row identifier * timestamp: bird GPS date/time position *
 sensor.type: GPS manuscript * tagid: bird transmitter ID *
 temperature: temperature vmanuscriptnk ENVI (see manusript methods). *
 snowDepth: snow depth via movebank manuscript manuscript methods. *
 snowCover: proportion snow cover via movebank ENVI (see manusript
 methods). * season: migration season * sex: bird sex * migrdistance:
 migration distance (km) * longbreedlat: breeding latitude * longbreedlong:
 breeding longitude * mass: bird body mass (g) at capture * avgMinTemp:
 average minimum daily temperature (K) * avgSnowDepth: average daily snow
 depth (m) * avgSnowCover: average daily snow coverage proportion * nrows:
 number of days during winter for which temperature or snow data was
 available based on days when GPS transmitters recorded positions ####
 File: date-filtered-winter-locations.csv **Description:** see R
 scripts. 'NA' cells refers to missing data (either missing or
 not included because not applicable to the analyses). ##### Variables *
 timestamp: bird GPS date/time position * long: bird longitude at timestamp
 * lat: bird latitude at timestamp * sensor.type: GPS manuscript * tagid:
 bird transmitter ID * temperature: temperature viamanuscript ENVI (see
 manusript methods). * snowDepth:  snow depth via movebank manuscript
 manuscript methods. * snowCover: proportion snow cover via movebank ENVI
 (see manusript methods). * argos.lc: argos GappyioWaslass * date: date *
 year: migration year * seathe son: migration season * sex: bird sex *
 gappy: was winter gappy in terms of GPS data from transmitter? *
 migrdistance: migration distance (km) * longbreedlat: breeding latitude *
 longbreedlong: breeding longitude * mass: bird body mass (g) at capture
 #### File: Gappy-Winter-Data-Temp-Snow.csv-4319131622421889556.csv
 **Description:** see R scripts. 'NA' cells refers to missing
 data (either missing or not included because not applicable to the
 analyses). ##### Variables * tagid: bird transmitter ID * timestamp: bird
 GPS date/time position * location-lat: bird latitude at timestamp *
 location-longmanuscriptngitude at TemperaturenowCover: proportion
 Movebankcover via manuscriptNVI NVI (see manusript methods). *
 temperature: temperature viamanuscript ENVI (see Sensoript methods). *
 snowDepth:  snow depth via movebank ENVI (see manusript methods). *
 sensor.type: GPS sensor type #### File: Conway-GPS_temperature.csv
 **Description:** see R scripts. 'NA' cells refers to missing
 data (either missing or not included because not applicable to the
 analyses). ##### Variables * timestamp: bird GPS date/time position *
 location-long: bird longitude at timestamp * location-lat: bird latitude
 at timestamp * sensor-type: GPS sensor type * individual-local-identifier:
 bird trmanuscript ID * NCEP NARR SFC Temperature at Surface: temperature
 via movebank ENVI (see manusript methods). #### File: Mapping_RLHA.csv
 **Description:** see R scripts for use. 'NA' cells refers to
 missing data (either missing or not included because not applicable to the
 analyses). ##### Variables * tagid: bird transmitter ID * season:
 migration season * sex: bird sex * migrdistance: migration distance (km) *
 winterlat: wintering latitude * winterlong: wintering longitude *
 breedlat: breeding latitude * breedlong: breeding longitude #### File:
 Kidd-GPS_snow-cover.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables *
 timestamp: bird GPS date/time position * location-long: bird longitude at
 timestamp * location-lat: bird latitude at timestamp * sensor-type: GPS
 sensor type * individual-local-identifier: bird transmittermanuscriptNARR
 SFC Snow Cover at Surface: proportion snow cover via movebank ENVI (see
 manusript methods). #### File: Kidd-GPS_snow-depth.csv
 **Description:** see R scripts for use. 'NA' cells refers to
 missing data (either missing or not included because not applicable to the
 analyses). ##### Variables * timestamp: bird GPS date/time position *
 location-long: bird longitude at timestamp * location-lat: bird latitude
 at timestamp * sensor-type: GPS sensor type * individual-local-identifier:
 bird manuscripter ID * NCEP NARR SFC Snow Depth at Surface:  snow depth
 via movebank ENVI (see manusript methods). #### File:
 Kidd-GPS_temperature.csv **Description:** see R scripts for
 use. 'NA' cells refers to missing data (either missing or not
 included because not applicable to the analyses). ##### Variables *
 timestamp: bird GPS date/time position * location-long: bird longitude at
 timestamp * location-lat: bird latitude at timestamp * sensor-type: GPS
 sensor type * individual-local-identifier: bird manuscripter ID * NCEP
 NARR SFC Temperature at Surface: temperature via movebank ENVI (see
 manusript methods). #### File: Snow-Temperature-Complete-Kidd-Conway2.csv
 **Description:** see R scripts for use. 'NA' cells refers to
 missing data (either missing or not included because not applicable to the
 analyses). ##### Variables *  row, index * timestamp: bird GPS date/time,
 position * location. long: bird longitude at times, tamp * location.lat:
 bird latitude at timestamp * sensor.type: GPS sensor type * individual.
 local.Movebanker: bird trmanuscript ID * NCEP.NARR.SFC.Temperature.
 At.Surface: temperature via Movebank ENVI (see manuscript). *
 NCEP.NARR.SFC.Snow.Depth. at.Surface:  snow depth via movebank ENVI (see
 manuscript method manuscriptNARR.SFC.Snow.Cover. at.Surface: proportion
 snow cover via movebank ENVI (see manusript methods). * argos.lc: argos
 location class #### File: 1_Fasting-Thermal_compilation.R
 **Description:** first R script for analyses of fasting endothermic
 animals and the thermal tolerance hypotheses. #### File: ArrivalTime.R
 **Description:** R script for analyses of arrival time hypothesis. ####
 File: DietSpecialization.R **Description:** R script for analyses of
 dietary specialization and dietary preference hypotheses. #### File:
 Figure1-map-code.R **Description:** R script analysis of Figure 1 map.
 #### File: FlightEfficiencyPCA.R **Description:** R script for analyses of
 flight efficiency hypothesis. #### File: SocialDominance.R
 **Description:** R script for analyses of social dominance hypotheses.
 #### File: 2_Fasting-Thermal_Analysis.R **Description:** second R script
 for analyses of fasting endurance and thermal tolerance hypotheses. ####
 File: 3_Fasting-Thermal_Analysis.R **Description:** third R script for
 analyses of fasting endurance and thermal tolerance hypotheses. #### File:
 BodySize.R **Description:** R script for analyses of predictions related
 to body size. #### File: CarryOverEffects.R **Description:** first R
 script for analyses of carry-over effects hypothesis. #### File:
 Predicted_Migration_Distances.R **Description:** R scripts for analyses
 used to generate inferred migration distances from empirical data. ##
 Code/software All analyses were conducted using free software from the R
 statistical environment, and scripts are provided herein. Loaded packages
 are detailed within each R script. ## Access information Other publicly
 accessible locations of the data: * NA Data was derived from the following
 sources: * We used the Environmental-Data Automated Track Annotation
 feature provided through Movebank (Dodge et al. 2013) to compile winter
 temperature, snow cover, and snow depth information associated with
 rough-legged hawk GPS or Argos locations. We utilized the following three
 environmental attributes for our temperature and snow analysis because
 they were readily accessible and fully covered the broad geographic scope
 of our study: (1) National Center for Environmental Prediction’s (NCEP)
 North American Regional Reanalysis (NARR) Temperature at Surface (in
 Kelvin); (2) NCEP NARR Snow Cover at Surface (% cover); and (3) NCEP NARR
 Snow Depth at Surface (in meters). Environmental data were collected at a
 spatial and temporal granularity of 0.3 degrees and 3 hours, respectively;
 and were interpolated using the inverse distance weighted method when data
 were missing (Dodge et al. 2013).