DOI: 10.5061/dryad.2z34tmppj
title: Pelagic seabirds reduce risk by flying into the eye of the storm

description: Cyclones can cause mass mortality of seabirds, sometimes wrecking
 thousands of individuals. The few studies to track pelagic seabirds during
 cyclones show they tend to circumnavigate the strongest winds. We tracked
 adult shearwaters in the Sea of Japan over 11 years and find that the
 response to cyclones varied according to the wind speed and direction. In
 strong winds, birds that were sandwiched between the storm and mainland
 Japan flew away from land and towards the eye of the storm, flying within
 ≤ 30 km of the eye and tracking it for up to 8 hours. This exposed
 shearwaters to some of the highest wind speeds near the eye wall (≤ 21 m
 s-1), but enabled them to avoid strong onshore winds in the storm’s wake.
 Extreme winds may therefore become a threat when an inability to
 compensate for drift could lead to forced landings and collisions. Birds
 may need to know where land is in order to avoid it. This provides
 additional selective pressure for a map sense and could explain why
 juvenile shearwaters, which lack a map sense, instead navigating using a
 compass heading, are susceptible to being wrecked. We suggest that the
 ability to respond to storms is influenced by both flight and navigational
 capacities. This may become increasingly pertinent due to changes in
 extreme weather patterns. 
description: Methods are detailed in the manuscript.
description: Summary of Attributes
 <strong>StormDt</strong>: Storm date (UTC) from
 IBTrACS for each eye location.
 <strong>StormID</strong>: Storm ID from IBTrACS for
 each storm. StormID is given in IBtracs codes and
 corresponds to the storms: 2010240N15142
 -&gt;  "Kompasu" 2010243N12146
 -&gt;  "Malou" 2010249N24125 -&gt; 
 "Meranti" 2014260N13135 -&gt; 
 "Fung-Wong" 2015226N12151 -&gt; 
 "Goni" 2015249N18142 -&gt; 
 "Etau" 2017252N14147 -&gt; 
 "Talim" 2018228N13145 -&gt; 
 "Soulik" 2018230N13156 -&gt;
 "Cimaron" 2018239N13159 -&gt;
 "Jebi" 
 <strong>Date</strong>: Date of each hour of
 observations (UTC).
 <strong>flghtID</strong>: Flight ID of each hour of
 observations. <strong>StrmLng</strong>:
 Storm longitude for each storm eye location from IBTrACS. 
 <strong>StormLt</strong>: Storm latitude for each
 storm eye location from IBTrACS.      
 <strong>StormDirHourly</strong>: Storm eye direction
 of travel for each IBTrACS location.    
 <strong>HourDate</strong>: Date and hour (UTC) for
 each hour of observations.
 <strong>Hour</strong>: Hour of observations
 (UTC). <strong>IntPolLng</strong>:
 Interpolated longitude of bird locations based on all longitudes within
 each hour of observations.
 <strong>IntPolLat</strong>: Interpolated latitude of
 bird locations based on all latitudes within each hour of
 observations.
 <strong>StrmSideHourly</strong>: The side at which
 the storm eye was located for each hour of observations. This is: “West”
 when the storm eye was located over the Sea of Japan, “JapanWest” when the
 eye was located over the West side of Japan and over land, “East” when the
 eye was located over the Western Pacific at the East of Japan and
 “JapanEast” when the eye was located over the East side of Japan and over
 land. <strong>BrdSideHourly</strong>: Same
 as “<strong>StrmSideHourly</strong>” above, but for bird
 locations. <strong>Spd_m_sHourly</strong>:
 Mean ground speed (m s<sup>-1</sup>) based on the bird GPS
 observations per hour.
 <strong>airspeedHourly</strong> : Mean airspeed (m
 s<sup>-1</sup>) based on the bird GPS observations per
 hour. <strong>dstnc_mHourly</strong>: Mean
 geodesic distance (metres) covered by a bird based on the GPS observations
 per hour. <strong>BirdStormDist</strong>:
 Mean distance (km) between a bird and the storm eye based on all GPS
 observations and the location of the eye of the storm (IBTrACS), per
 hour. <strong>BirdLandDist</strong>: Mean
 distance (km) between a bird and land based on all GPS observations and
 the closest location on land (for each GPS observation), per
 hour. <strong>ColonyPresence</strong>:
 Binomial variable indicating whether a bird was located at the colony in
 Awashima Island (“YES”) or not (“NO”).
 <strong>WindSpeed</strong>: Mean wind speed (m
 s<sup>-1</sup>) at bird locations estimated using ERA5, per
 hour. <strong>WindDirHourly</strong>: Mean
 wind direction (°) at bird locations estimated using ERA5, per
 hour. <strong>flWndAn360Hourly</strong>:
 Mean angle (°) between a bird’s flight headings (GPS) and wind’s
 directions at the bird’s locations (ERA5), for all GPS observations per
 hour. This ranges from 0° to 360°, with 0° indicating tailwind, 360°
 headwind, 90° crosswind coming from the right side of the bird and 270o
 crosswind coming from the left side of the bird.
 <strong>flWndAnHourly</strong>: Same as
 “flWndAn360Hourly” but converted to 0°–180°. 0o indicates tailwind,180°
 headwind and 90° crosswind from either side of the bird. 
 <strong>RelFlghtStrmDirHourly</strong>: Mean bird
 flight direction in relation to the storm eye’s location for each hour
 indicating whether a bird travelled straight towards the eye (0°),
 straight away from the eye (360°), perpendicular straight to the right of
 the eye (90o) and perpendicular straight to the left of the eye
 (270°).
 <strong>RelFlghtStrmDirHourly180</strong>: Same as
 “RelFlghtStrmDirHourly” but converted to 0°–180°. 0° indicates flight
 straight towards the eye’s location,180° straight away and 90° away
 (perpendicular) to the left or to the right of the eye.
 <strong>StrmAngHourly</strong>: Mean angle (°) that a
 bird would have to travel from each current GPS location to fly straight
 towards the eye’s location, per hour of observations .
 <strong>RelBrdPosStrmDirHourly</strong>: Mean angle
 (°) between a bird’s locations (GPS) and the direction the storm eye was
 travelling (IBTrACS), for all GPS locations per hour. This ranges from 0°
 to 360°, with 0° indicating that a bird was located directly in front of
 the eye (i.e. the eye was travelling straight to the bird’s location),
 360° indicating that a bird was located straight behind the eye (i.e. the
 eye was travelling straight away from the bird’s location), 90° indicating
 that the bird was located at the right (i.e. at the East) with the eye
 travelling perpendicular to the left of the bird (i.e. towards the West)
 and 270° indicating that the bird was located at the left (i.e. at the
 West) of an eye, with the eye travelling perpendicular to the right (i.e.
 towards the East).
 <strong>BirdPosRelToStormDir</strong>: : Same as
 “RelBrdPosStrmDirHourly” but converted to 0°–180°. 0° indicates that a
 bird is located straight in front of the direction that the storm eye was
 travelling,180° straight behind the direction that the storm eye was
 travelling and 90° perpendicular either to the left or right.
 <strong>flAsiaAn360Hourly</strong>: Mean angle (°)
 between a bird’s flight headings (GPS) and the closest location on land,
 for all GPS locations per hour. This ranges from 0° to 360°, with 0°
 indicating flight straight towards the closest point on land, 360°
 indicating flight straight away, 90° flight straight to the right of the
 closest point on land and 270° flight straight to the left of the closest
 point on land (perpendicular).
 <strong>FlightDirRelToLand180</strong>: Same as
 “flAsiaAn360Hourly” but converted to 0°–180°. 0° indicates flight straight
 towards the closest point on land,180° straight away and 90°away
 (perpendicular) to the left or to the right of the closest point on
 land. <strong>SampleSize</strong>: Number
 of GPS fixes per hour.
 <strong>SampleSizeNormalised</strong>: Normalised
 number of GPS fixes per hour. This attribute was estimated by dividing the
 “SampleSize” of each hour, with the mean sample size of all hours of
 observations.   
 <strong>StormLandDist</strong>: Geodesic distance
 (km) between the eye of a storm at a specific hour (IBTrACS) and the
 closest point on land.
 <strong>StormDirRelToLand180</strong>: Mean angle (°)
 between an eye’s direction of travel (IBTrACS) and the closest point on
 land, for all storm’s eye locations per hour. This ranges from 0° to 180°,
 with 0° indicating a storm eye of the storm travelling straight towards
 land, 180° indicating an eye travelling straight away and 90° indicating
 that an eye was travelling perpendicular to the closest location on land
 either to the left or to the right. <strong>RightOrLeft</strong>:
 This variable is included
 in the datasets of the agent-based model simulations. It indicates whether
 an agent was predicted to move to the right of the storm eye, indicated by
 a value of “1”, or to the left with a value of “0”.