DOI: 10.5061/dryad.xwdbrv1kz
title: Data from: Intrinsic and extrinsic factors modulating vigilance and foraging in two gregarious foragers

description: Individuals need to trade-off vigilance and foraging, but species differ
 in how they manage this. We explored the effects of both intrinsic and
 extrinsic factors on individual vigilance/foraging patterns in two
 migratory, gregarious bird species markedly differing in body size and
 foraging strategies, the Greylag Goose Anser anser and the Common Crane
 Grus grus, during the non-breeding period. We show that vigilance in
 individuals of both species decreased with increasing group size and
 distance from the edge of the group. However, the two species varied how
 they allocated the freed up time. While cranes allocated the resulting
 time to foraging, the same did not occur in geese. In addition, we
 investigated changes in individual position in the group (i.e., peripheral
 vs. central or vice versa) and how they elicited a prompt behavioral
 change (i.e., vigilance vs. foraging or other activity). We also explored
 whether the time elapsed since arrival in non-breeding grounds and
 proximity to spring migration affected vigilance patterns. We analyzed
 data using generalized linear mixed models (GLMMs). Analyses were
 conducted in three steps. First, we fitted species-specific models to
 explore the factors influencing indices of vigilance and foraging in the
 two species. Then, we fitted models to investigate the general differences
 in vigilance/foraging levels between the two species. We calculated the
 vigilance rate (VR), i.e. the no. of vigilance bouts divided by minutes of
 observation, the proportion of time in vigilance (PTV) and the proportion
 of time foraging (PTF), and used them as response variables. Eventually,
 we focused on repositioning events in the position of individuals within a
 flock, to evaluate whether reshuffling elicited any change in vigilance
 and foraging activity immediately after the repositioning. We analyzed
 presence/absence of vigilance and foraging behaviors after repositioning
 events (both active and passive due to rearrangement) in the observed
 individual’s position within a flock. Both in the first and in the third
 steps, we fitted separate models for each species, whereas in the second
 step we fitted one model for geese and cranes combined. In all steps, we
 used a multi-model selection approach, through which we ranked all
 possible candidate models, including the null model. Results allowed to
 disentangle the role of multifactorial determinants of vigilance and
 foraging, in turn increasing our understanding of forces driving the
 evolution of behavior in group-living animals.
description: Our study was conducted in the Northern sector of the Maremma
 Regional Park (42°39′N, 11°05′E), a protected area in Tuscany (Central
 Italy). Behavioral observations were conducted between the end of October
 and the end of January, during two consecutive wintering seasons (2019/20
 and 2020/21). Observations were carried out from vantage points 5-7 m
 above the ground, whilst the observer maintained a 200-500 m distance from
 the flocks in order to minimize potential alteration of birds’ behavior.
 Further information on behavioral observations and data collection can be
 found in section 2.2 of the paper. All the analyses can be replicated by
 following the statistical procedure and by using the software described in
 the Methods section of the paper.
description: # Data from: Intrinsic and extrinsic factors modulating vigilance and
 foraging in two gregarious foragers
 ## Description of the data
 and file structure Two datasets are provided to reproduce the analyses of
 the paper "Intrinsic and extrinsic factors modulating vigilance and
 foraging in two gregarious foragers". Each file has its legend
 including variables' names and descriptions. The file
 'Dataset_drivers.xlsx' can be used to reproduce the analyses on
 the species-specific drivers of vigilance and foraging behavior in geese
 and cranes (section 3.1 of the paper), as well as the interspecific
 analysis (section 3.2 of the paper). The file
 'Dataset_repositioning_events.xlsx' can be used to reproduce the
 analyses on the species-specific behavioral changes in relation to spatial
 position in geese and cranes (section 3.3 of the paper). All the analyses
 can be replicated by following the statistical procedure and by using the
 software described in the Methods section of the paper. ## Sharing/Access
 information The data are derived from the paper "Intrinsic and
 extrinsic factors modulating vigilance and foraging in two gregarious
 foragers". ## Code/Software All the analyses can be replicated by
 following the statistical procedure and by using the software described in
 the Methods section of the paper.