Identifying volatile organic compounds used for olfactory navigation by homing pigeons

Area of Science:

• Ornithology
• Chemical Ecology
• Animal Navigation

Background:

• Bird navigation is a complex phenomenon, with environmental odors long suspected as a key factor.
• Despite decades of research, the specific chemical cues birds use for homing remain largely unidentified.

Purpose of the Study:

• To identify the chemical identity of environmental odors used by birds for homeward navigation.
• To investigate the spatial and temporal distribution of volatile organic compounds (VOCs) that may serve as navigational cues.

Main Methods:

• Measurement of VOCs in the birds' home-loft, regional forest environments, and from an aircraft.
• Analysis of air mass trajectories in conjunction with bird GPS tracking data.
• Correlation of localized chemical concentrations with bird flight path alterations.

Main Results:

• Identification of distinct regional, horizontal, and vertical gradients in VOCs, including marine emissions (dimethyl sulfide - DMS), biogenic compounds (terpenoids), and anthropogenic aromatics.
• Observed temporal VOC changes consistent with a sea-breeze system.
• Demonstrated correlation between local DMS concentrations and predictable alterations in bird flight directions.

Conclusions:

• Regional-scale chemical gradients in VOCs provide a basis for an olfactory map usable by homing pigeons.
• Dimethyl sulfide (DMS) concentrations appear to significantly influence homing pigeon flight direction.
• This research provides concrete chemical evidence supporting the olfactory navigation hypothesis in birds.