DOI: 10.5061/dryad.79cnp5j0b
title: Gulls contribute to olive seed dispersal within and among islands in a Mediterranean coastal area

description: Aim: To analyse the role of non-frugivorous birds on seed dispersal, seed
 dispersal by gulls is expected to be especially instrumental in island
 ecosystems, as these have a smaller subset of frugivores when compared to
 the mainland, and because long-distance dispersal is required for plant
 colonization. Here we investigated the seed dispersal of olives by gulls
 among ten islands of the same archipelago to reveal if gulls contribute to
 long-distance seed dispersal including different islands, and how gulls’
 adaptation to domestic olives and individual differences in foraging
 activities affect their seed dispersal pattern.
 Location: Balearic Islands in the Western Mediterranean Sea,
 Spain Taxon: Yellow-legged gulls ( Larus michahellis), Domestic and wild
 Olives ( Olea europaea and O. europaea var. sylvestris) Methods: We
 developed seed dispersal models of the two ecotypes of olives dispersed by
 gulls across an archipelago, based on GPS tracking data, gut passage time,
 and seed viability. Results: Mean dispersal distances were 7.67 (±12.48)
 km in wild and 12.57 (±13.08) km in domestic olives. Seven-point one
 percent of wild and 8.5% of domestic olives were dispersed among islands.
 Among these, 8.2% of domestic seeds were transported from large to small
 islands where gull colonies are located, whereas wild olives were
 dispersed in more variable directions. Such dispersal pattern of two olive
 ecotypes were consistent despite the differences in dispersal distances
 among individuals. Main conclusions: Gulls contributed to long-distance
 olive seed dispersal including different islands. The seed dispersal of
 domestic olives to longer distances with specific directions may
 facilitate colonization and expansion of that variant if the conditions of
 seed deposition sites are suitable. Our findings indicate that gulls are
 relevant vectors for long-distance dispersal of large fleshy fruits in
 island ecosystems where specialist large frugivores are absent.
description: # Title of Dataset: Gull tracking data for the manuscript "Gulls
 contribute olive seed dispersal within and among islands in a
 Mediterranean coastal area" by Ando et al. The data contains GPS
 locations of 20 individuals of yellow-legged gulls *Larus michahellis* and
 other parameters which were used to develop the seed dispersal models in
 this study. ## Description of the Data and file structure This is a csv
 file available for R packages used in this study. Parameter list * fid: ID
 of each GPS point * location.long: Longitude of each GPS point *
 location.lat: Latitude of each GPS point * individual.local.identifier: ID
 of gull individual tags * Body.weight: Body weight of gulls (g) *
 study.local.timestamp: Timestamp of GPS positioning (yyyy/mm/dd hh:mm:ss)
 * Wild.olive.distribution: Presence (1) or absence (0) of wild olive
 vegetation in each GPS point * Night.stay: Nighttime GPS positioning (1)
 and daytime positioning (0) * Year: Year of data collection *
 individual\_id: Individual ID separated by years * dist: Distances from
 the previous GPS point (m) * timediff: Time difference from the previous
 GPS point (s) * speed: Gulls' speed s/h at each GPS point (m/s) *
 inland: GPS position inland (1) or sea (0) * ID\_LOC: Land use ID of
 CORINE Land Cover 2018 * islands: Name of islands in each GPS point
 Missing data is shown as "NA".