Insectivorous Birds Are Attracted by Plant Traits Induced by Insect Egg Deposition.

Area of Science:

• Ecology
• Animal Behavior
• Chemical Ecology

Background:

• Insectivorous birds consume various insect life stages, including eggs.
• Insect egg deposition can alter plant traits, influencing natural enemies like parasitoids.
• The role of egg-induced plant changes in attracting avian predators remains largely unexplored.

Purpose of the Study:

• To investigate if great tits (Parus major) and blue tits (Cyanistes caeruleus) are attracted to Scots pine (Pinus sylvestris) traits induced by pine sawfly (Diprion pini) egg deposition.
• To determine if birds use olfactory or visual cues from egg-induced plants for prey localization.

Main Methods:

• Dual-choice laboratory experiments presenting birds with egg-free vs. egg-induced pine branches.
• Gas chromatography-mass spectrometry (GC-MS) to analyze volatile organic compounds (VOCs).
• Spectrophotometric analysis to assess light reflectance differences in pine branches.

Main Results:

• Birds significantly preferred egg-induced pine branches over control branches.
• Egg-induced branches exhibited increased release of (E)-β-farnesene.
• Egg-induced branches showed altered light reflectance compared to control branches across the avian visual spectrum.

Conclusions:

• Avian predators can be attracted to plant traits modified by insect egg deposition.
• Induced volatile organic compounds and altered visual reflectance may serve as cues for birds to locate insect eggs.
• This study reveals a novel foraging strategy in birds, utilizing plant-mediated cues for prey detection.