A field test of the effects of body composition analysis by quantitative magnetic resonance on songbird stopover behaviour

Abstract

Quantitative magnetic resonance (QMR) is a non-invasive technology used to measure body composition. It has great potential to advance the study of energetics and fuel use of migratory birds. However, there is concern that exposure to a strong magnetic field during QMR analysis could affect magnetite-based geomagnetic senses of migratory songbirds which may be important for orientation and navigation. We used radiotelemetry and capture-mark-recapture analysis to test for effects of QMR analysis on stopover duration and departure orientation. There was no evidence from radiotelemetry data that QMR analysis influenced minimum stopover duration or departure orientation of Black-throated Blue Warblers (Setophaga caerulescens) in the spring or fall, or Magnolia Warblers (Setophaga magnolia) in the spring. Capture-mark-recapture analysis of White-throated Sparrow (Zonotrichia albicollis) ringing data showed no effects of QMR on transiency or recapture probability, but a slight increase in estimated stopover duration (days) in the fall. Our study provides evidence that stopover duration and departure orientation of migrating songbirds are not significantly affected by QMR analysis with the exception of fall stopover duration estimates from mark-recapture models, and that QMR is a safe technique for the study of birds in the field.