DOI: 10.5061/dryad.6b55m22
title: Data from: Body stores persist as fitness correlate in a long-distance migrant released from food constraints

description: Long-distance migratory birds rely on acquisition of body reserves to fuel
 their migration and reproduction. Breeding success depends on the amount
 of body reserve acquired prior to migration, which is thought to increase
 with access to food at the fuelling site. Here we studied how food
 abundance during fuelling affected time budgets and reproductive success.
 In a regime of plenty, we expected that (1) limitations on food harvesting
 would become lifted, allowing birds to frequently idle, and (2) that birds
 would reach sufficient fuel loads, such that departure weight would no
 longer affect reproductive success. Our study system comprised brent geese
 (Branta b. bernicla) staging on high-quality agricultural pastures.
 Fuelling conditions were assessed by a combination of high-resolution
 GPS-tracking, acceleration-based behavioural classification,
 thermoregulation modelling, and measurements of food digestibility and
 excretion rates. Mark-resighting analysis was used to test for
 correlations between departure weight and offspring recruitment. Our
 results confirm that birds loafed extensively, actively postponed fuelling
 in early spring, and took frequent digestion pauses, suggesting that
 traditional time constraints on harvest and fuelling rates are absent on
 modern-day fertilized grasslands. Nonetheless, departure weight remained
 correlated with recruitment success. The persistence of this correlation
 after a prolonged stopover with access to abundant high-quality food,
 suggests that between-individual differences in departure condition are
 not so much enforced by food quality and availability during stopover, but
 reflect individual quality and longer-lived life-history traits, such as
 health status and digestive capacity, which may be developed before the
 fuelling period.
description: GPS, accelerometer and
 environmental data for individually tracked brent geeseGPS and accelerometer
 tracking data of individual dark-bellied Brent geese, linked to metadata
 on bathymetry and tidal information.gps_acc_brent.csvField observations of defecations and antagonistic interactionsField observations of defecations and antagonistic interactions of dark-bellied brent geese on Terschelling islandbehavioural_observations.csvBiometry and resightings of dark-bellied brent geeseBiometry and resightings of dark-bellied brent geese captured on Terschelling island in 2005, 2010, 2011, 2013, 2014 (i.e. successful breeding years in the arctic when birds returned with juveniles) as obtained from the geese.org database (accessed 24 Feb 2016).catches_resightings.csvsampling locationslocations of exclosures and locations of 4 m^2 circles in which geese droppings were collectedstations.csvgrass and brent goose excreta samplingPasture grass and excreta sampling and chemical analysis, goose excreta densities and vegetation heightgrass_droppings_sampling.csvweight of individual brent goose excretaDry weights of individual brent goose excretadropping_weights.csvenergy and ash content of grass and excretabom calory measurements and ash content of pasture grass and brent goose excretabom_calory-ash.csv