Light-dependent magnetoreception in birds: does directional information change with light intensity?

Area of Science:

• Ornithology
• Animal Behavior
• Sensory Ecology

Background:

• Avian migratory orientation is fundamentally linked to light-dependent magnetoreception.
• Magnetoreception in birds requires specific blue and green light wavelengths.
• The influence of light intensity on magnetic compass function remains underexplored.

Purpose of the Study:

• To investigate intensity-dependent effects on magnetic compass orientation in Australian silvereyes (Zosterops lateralis).
• To determine how varying light levels of monochromatic green light impact migratory direction.

Main Methods:

• Testing Australian silvereyes during autumn migration under monochromatic green light (565 nm) using light-emitting diodes.
• Exposing birds to different light intensities ranging from 0.0002 to 0.0150 W/m(2).
• Analyzing orientation behavior and activity levels at each light intensity.

Main Results:

• Birds exhibited normal orientation at moderate green light intensities (0.0021 and 0.0075 W/m(2)).
• At low light intensity (0.0002 W/m(2)), activity decreased, and orientation scatter increased, but migratory direction was maintained.
• High light intensity (0.0150 W/m(2)) induced a counterclockwise shift in direction, with birds preferring west-northwest instead of north.

Conclusions:

• Light intensity significantly modulates magnetic compass orientation in Australian silvereyes.
• High light levels may disrupt the magnetoreception system, potentially by altering the balance of light wavelengths perceived by the birds.
• These findings highlight the complex interplay between light quality, intensity, and avian navigation.