DOI: 10.5061/dryad.kwh70rz0t
title: First explorations: ontogeny of central-place-foraging directions in two tropical seabirds

description: A widespread hypothesis for the ontogeny of behaviour and decision-making
 is the early-exploration-later-canalization hypothesis. It postulates that
 juveniles are more exploratory and adults more consistent in their
 behavior. In addition, it is often assumed that naïve juveniles could
 overcome the costs of individual experience building by copying more the
 decisions of others than adults (early-conformism-later-self-defining
 hypothesis). Here we compare the central-place-foraging movements of
 adults and post-fledging juveniles in their first flights around the
 colony before dispersal and migration, in two sympatric species of
 tropical seabirds: red-footed boobies and great frigatebirds. Using GPS
 records of individual movements, we analyzed the foraging directions of
 seabirds from the colony across successive trips. Juveniles of both
 species showed significant within-individual consistency in foraging
 direction but at lower levels than adults. Juveniles leaving the colony
 within the same time-window showed significant but low between-individual
 resemblance in foraging direction, at levels similar to adults. In both
 species, homing efficiency was lower in juveniles than in adults. Juvenile
 foraging directions were initially influenced by wind conditions,
 particularly in low-wing-loading frigatebirds. Wind conditions
 progressively lost influence on juvenile foraging directions during their
 first weeks of flights. In contrast within-individual consistency,
 between-individual resemblance and homing efficiency did not show signs of
 progression in juveniles. Our results support the
 early-exploration-later-canalization hypothesis but not the
 early-conformism-later-self-defining hypothesis. Relaxed constraints on
 self-feeding efficiency could favour high variability in post-fledging
 tropical seabirds. Our simple approach could be applied to further test
 these hypotheses by comparing strategies across a wide range of
 central-place foragers.
description: Birds were captured on nest and fitted with GPS-data loggers with
 adhesive tape. From the GPS tracks we identified each single foraging
 excursions from the colony, each one corresponds to one row in the
 provided dataset (TripMetadata.csv). For each foraging
 trip we extracted statitistics such as the distance and direction from
 colony along diverse points of the track: maximum range from colony,
 different % of the maximum range from colony on both the way out and the
 way in, or the first point reaching 10, 20, etc. km from the colony both
 on the way out and the way in. From each of these points we also extracted
 a standardized straightness index. Finally we also
 added information on wind (u,v as available from NOAA servers, but also
 transformed into other referentials e.g. wind direction and speed (polar
 referential) or in parallel/perpendicular to flight direction
 referential. See M&M for more details on data
 collection and the analyses reported in the manuscript.
 All analyses presented can be replicated following the script
 StatisticalAnalyses&Figures.R, as well as all figures except for
 Fig1 which requires original tracking data. Notably,
 analyses on resemblance call on two specific scripts to establish
 resemblance between all possible pairs of trips (for juv and ad,
 respectively). Sensitivity analyses can be carried by
 changing parameter values, or in the case of changing the definition of
 trip directions (e.g. first 10km) by using the script
 DirectionAt10km.