DOI: 10.5061/dryad.fbg79cp2d
title: Data from: Differences in foraging range between white-tailed tropicbirds breeding on inner and outer Seychelles Islands

description: The foraging ecology and distribution of Phaethontiformes, an order of
 tropical seabirds, remains generally poorly understood, despite being
 essential to inform their conservation. Here, we tracked, for the first
 time, the foraging movements of breeding white-tailed tropicbirds Phaethon
 lepturus, a common but poorly studied seabird, in the Indian Ocean. We
 compared the foraging movements and habitat preferences of 2 populations,
 one from Aride Island in the inner Seychelles and the other from Aldabra
 Atoll in the outer Seychelles, ca. 1200 km to the southwest. We found
 considerable differences in foraging trip metrics between populations,
 with birds from Aride having an average foraging range 2 times greater
 (231 km on Aride vs. 105 km on Aldabra), and both populations feeding far
 beyond the protected areas around their respective colony. We also found
 differences in foraging range between incubation and chick-rearing stages
 and sexes. Using habitat models, we highlight the birds’ preference for
 deep waters, which may explain the greater foraging range of Aride birds,
 although human activities may also play a role. Our study provides
 unprecedented insight into the foraging ecology of white-tailed
 tropicbirds in the Western Indian Ocean.
description: The data collection methods are described in the paper and its
 electronic supplementary materials.
description: # Data from: Differences in foraging range between white-tailed
 tropicbirds breeding on inner and outer Seychelles Islands
 This dataset is published
 in the following paper: Ensanyar-Volle O, Appoo J, Bunbury N, Clucas G,
 Khan N, Rocamora G, Sanchez C, Fayet AL (2023) Differences in foraging
 range between white-tailed tropicbirds breeding on inner and outer
 Seychelles Islands. *Marine Ecology Progress Series* 724, 141–154,
 [https://doi.org/10.3354/meps14454]() There are two datasets: one with the birds' **GPS data** and
 associated metadata (*GPS_data.csv*), and one with the birds’ **GPS
 foraging locations and environmental variables** used in the Generalised
 Additives Models (GAMs) (*GAM_data.csv*). ## Description of the data and
 file structure All variables in each file are listed below. Details about
 the methods employed to obtain/calculate the variables are in the above
 paper.  **GPS_data.csv** Each row corresponds to a GPS location – note
 these data are interpolated (see paper for details).  ·         Lon:
 interpolated longitude, in decimal degrees ·         Lat: interpolated
 latitude, in decimal degrees ·         Bird: unique ring number to
 identify the bird ·         Local datetime: date and time in local time
 (GMT+4) ·         Sex: sex of the bird obtained from DNA (M=male,
 F=female, NA=unknown) ·         Colony: birds’ breeding colony, Aldabra
 Atoll or Aride Island ·         Stage: breeding stage (INC=incubation, CR=
 chick-rearing, INCCR=the egg was still intact when the trip started, but
 the chick had hatched by the time the trip ended) ·         Behaviour_HMM:
 behaviour (rest, foraging or relocation) as classified by Hidden Markov
 Models ·         Date: date ·         Trip_nb: trip number (each trip of
 each bird gets a unique number) **GAM_data.csv** Each row corresponds
 either to a foraging location recorded by GPS, or to a pseudo-random
 location used to generate a null distribution for the GAMs (see the paper
 for details). ·         Lon: longitude, in decimal degrees (note, for the
 “real” points this is interpolated) ·         Lat: latitude, in decimal
 degrees (note, for the “real” points this is interpolated) ·         Bird:
 unique ring number to identify the bird ·         Colony: birds’ breeding
 colony, Aldabra Atoll or Aride Island ·         Sex: sex of the bird
 obtained from DNA (M=male, F=female) ·         Trip_nb: trip number (each
 trip of each bird gets a unique number) ·         Datetime: date and time
 in local time (GMT+4) ·         Stage: breeding stage (INC=incubation, CR=
 chick-rearing) ·         Distance_from_nest_km: distance from the nest, in
 km ·         Date: date ·         chlA_monthly_mean: average chlorophyll A
 level at this location over the past month, in mg.m-3 ·        
 SST_monthly_mean: average SST at the location in the past month, in
 degrees Celsius  ·         Bathymetry:   water depth at the location, in m
 ·         Dist_seamount: distance to nearest seamount, in km         
 ·         wind_speed: wind speed at the location and time, in m.s-1
 ·         sum_fishing_effort: total fishing effort at that location during
 the study period, in hours. NA values mean no data were available for this
 location during the study period. ·         slope_degrees: slope of the
 sea floor at the location, in degrees     Location_type: whether the
 location is a real foraging location recorded by a GPS logger (“real”) or
 a pseudo-randomly generated location (“pseudo”) ## Sharing/Access
 information The GPS data are also available on the BirdLife Seabird
 Tracking Database.