DOI: 10.5061/dryad.hx3ffbgjw
title: Data for: Intra- and interspecific variation in trace element concentrations in feathers of North European Trans-African migrants

description: The knowledge of migratory connectivity is important for understanding the
 potential drivers of populations and it is thus important for conservation
 implications. Migratory connectivity of species can be studied using
 exogenous, such as rings and transmitters, or endogenous markers, such as
 stable isotopes and trace elements. The use of trace elements has been
 much less frequently studied compared to stable isotopes. Trace elements
 can be studied from the feathers of birds and this does not necessarily
 require trapping of individuals. Here we studied the variation of 18
 different trace elements in feathers of two long-distance trans-African
 migrants, willow warblers Phylloscopus trochilus and barn swallows Hirundo
 rustica, using body feathers of museum specimens of birds from Finnish
 breeding grounds. The trace elements were measured using Laser-Ablation
 Inductively-Coupled-Plasma Mass-Spectrometry. We show that trace element
 concentrations were relatively stable along the rachis within the same
 feather except in Ni and S, which showed a quadratic pattern. In general,
 variation within feathers of the same individuals was smaller than in
 feathers between individuals for most elements. Furthermore,
 concentrations of 11 trace elements showed significantly higher
 concentrations in willow warbler feathers collected in spring than in
 autumn, moulted in African wintering grounds and European breeding
 grounds, respectively. Last, concentrations of seven trace elements were
 significantly higher in the spring feathers of willow warblers compared to
 barn swallows. This suggests that trace elements could be used to separate
 moulting grounds of the birds on the larger scale within the same species,
 but also sampling design should be carefully considered.
description: The available dataset and R Script support the paper "Intra-
 and interspecific variation in trace element concentrations in feathers of
 North European Trans-African migrants", which will be published by
 the Journal of Avian Biology (2023). The uploaded files
 are the following: 
 Trace_element_feathers.csv: this is the dataset that contains
 the information used in the paper's analyses. Each row referst to a
 measurement spot along a feather's rachis. The columns contain the
 following information: A running index
 An indication of which spot is being measured
 The concentration of each of the 20 elements analysed for the
 paper at the given spot An identifier for the feather
 to which the measurement spot belongs An identifier
 for the individual to which the feather belongs
 Season during which the feather was collected (spring /
 autumn) Species to which the feather belonged (barn
 swallow / willow warbler) Number of the measurement
 spot along the rachis A code for the individual (same
 information as the individual identifier) A code for
 the feather (same information as the feather identifier)
 Trace_element_feathers_analysis.R:  this
 is an R file that should open the script containing our analyses. The
 workflow roughly follows the paper, and it is divided into sections:
 Data import Data cleaning and
 formatting Modelling
 Plotting
description: Trace_element_feathers.csv can be opened with a wide variety of
 programmes, such as Microsoft Excel, LibreOffice Calc or R. It is a CSV
 file that uses commas as separators, points as decimal separators and has
 a header line. Missing values are represented by "NA".
 Trace_element_feathers_analysis.R can be opened with R or
 RStudio.