DOI: 10.5061/dryad.k3j9kd5cf
title: Data from: Comparative analysis of the plasma metabolome of migrating passerines: Novel insights into stopover metabolism

description: During long-distance migration, many birds experience periods of either
 prolonged fasting (during endurance flights) or extensive feeding (during
 stopovers). Despite decades of research on avian metabolism during
 migration, many questions have remained unanswered, as such research
 mainly focused on targeted metabolites and fat metabolism. Here, we
 examined the plasma-metabolome of two migrating passerine species before
 they crossed the Sahara Desert. Birds were sampled at two sites populated
 by Pistacia trees bearing fat-rich fruits and at an additional site
 dominated by blooming Eucalyptus trees. The blood samples were analyzed
 using both GC-MS and LC-MS, using an untargeted approach. Examination of
 metabolic pathways activated during stopovers indicated a crucial role for
 cycling glucose through the Cori and Cahill cycles in resting and recovery
 processes. This novel perspective, conducted on free-ranging birds,
 suggests the evolution of avian insulin resistance due to factors such as
 endurance exercise, fasting, and a preference for fatty acid oxidation
 during migration, akin to cell trauma recovery. We detected significant
 inter-site variations in birds' polar and lipophilic metabolic
 profiles. We interpret the differences in the polar metabolites to be
 associated with the physiological state of the birds, with birds that are
 considered to have landed in the night prior to capture showing different
 metabolic profiles compared to birds that have spent more time at the
 stopover site. In contrast, distinctions in the lipophilic profiles of
 birds were associated with variations in the primary food source that was
 available to them in the different sites. This study underscores the
 challenge of interpreting commonly used indicators for assessing migrating
 birds' physiological state, which was predominantly derived from
 lipid metabolism in complex ecological systems.
description: # Comparative analysis of the plasma metabolome of migrating passerines:
 Novel insights into stopover metabolism --- The files presented here are
 untargeted metabolomic data for lipid (LC-MS) and polar (GC-MS)
 metabolites. The files GC_MS and LC_MS present the intensities of analytes
 in birds plasma. ## Description of the Data and file structure
 GCblood_FACTORS_UN - Untargeted metabolomic data, extracted using GC-MS.
 Columns A-J are the relevant factors for the collected birds, and columns
 K-PH are the analytes names, including annotations when possible.
 Lipid_blood_FACTORS_UN - Untargeted metabolomic data, extracted using
 LC-MS. Columns A-I are the relevant factors for the collected birds,
 columns J-RC are the analytes' names, including annotations when
 possible. aminoAcid_All - targeted metabolomic data, extracted using
 GC-MS, Columns A-H are the relevant factors for the collected birds,
 columns I-V are the annotated amino acids. Three files represent the
 relative intensity of the analytes in the birds’ plasma, and include all
 relevant factors for the collected birds. For all files, fat score is on a
 scale of 0-8, as described in Kaiser (1993). * Body mass was measured in
 grams * wing is measured in mm * age is represented by J-juveniles and
 A-Adults * all analytes are represented by their relative intensities
 (unitless) NA means that age or sex could not be determined, or the
 measurement (wing/body mass/ fat score) was not taken.