Identifying volatile organic compounds used for olfactory navigation by homing pigeons

Nora Zannoni,Atif Raza,Anna Gagliardo,Stefan Kramer,Martin Wikelski,Chiara Seghetti,Jonathan Williams,Nijing Wang,Achim Edtbauer

doi:10.1038/s41598-020-72525-2

Abstract

Many bird species have the ability to navigate home after being brought to a remote, even unfamiliar location. Environmental odours have been demonstrated to be critical to homeward navigation in over 40 years of experiments, yet the chemical identity of the odours has remained unknown. In this study, we investigate potential chemical navigational cues by measuring volatile organic compounds (VOCs): at the birds’ home-loft; in selected regional forest environments; and from an aircraft at 180 m. The measurements showed clear regional, horizontal and vertical spatial gradients that can form the basis of an olfactory map for marine emissions (dimethyl sulphide, DMS), biogenic compounds (terpenoids) and anthropogenic mixed air (aromatic compounds), and temporal changes consistent with a sea-breeze system. Air masses trajectories are used to examine GPS tracks from released birds, suggesting that local DMS concentrations alter their flight directions in predictable ways. This dataset reveals multiple regional-scale real-world chemical gradients that can form the basis of an olfactory map suitable for homing pigeons.

Highlights

Many bird species have the ability to navigate home after being brought to a remote, even unfamiliar location
Measurements consisted of: (i) a pilot study to investigate the volatile organic compounds (VOCs) emitted by three representative local ecosystems surrounding the bird’s home aviary; (ii) a 2-month intensive field campaign at the bird’s home aviary to monitor VOCs along with meteorological variables; (iii) three flights on board of a Cessna aircraft to sample at ca. 180 m, within the birds typical flight altitude
Volatile organic compound mixing ratios were determined with state-of-the-art on-line and off-line analytical techniques (PTRMS and gas chromatograph (GC)–mass spectromter (MS)) and speciated in their isomeric and enantiomeric forms

Summary

Introduction

Many bird species have the ability to navigate home after being brought to a remote, even unfamiliar location. Air masses trajectories are used to examine GPS tracks from released birds, suggesting that local DMS concentrations alter their flight directions in predictable ways This dataset reveals multiple regional-scale real-world chemical gradients that can form the basis of an olfactory map suitable for homing pigeons. The sampled mixture is first separated through chromatography into its chemical components, which are ionized through electron ionization and detected in the mass spectrometer It is regarded as a hard ionization method (typically 70 eV), and often considered the technique of choice when specificity and chemical resolving power are requied HEI Homing efficiency index. It expresses how accurately the birds head homeward when actively flying Isomers Molecules or ions with identical chemical formula but different structure. It is regarded as a soft ionization method, and often considered the technique of choice for its ability in detecting trace amounts of chemicals with a fast response

Methods

Results

Conclusion