Insectivorous birds can see and smell systemically herbivore-induced pines

Area of Science:

• Ecology
• Animal Behavior
• Plant-Insect Interactions

Background:

• Insectivorous birds often detect herbivore-damaged trees.
• Previous research indicated birds respond to damaged trees without direct sensory contact with herbivores.
• The specific sensory cues (visual vs. olfactory) driving this attraction remained unclear.

Purpose of the Study:

• To determine if visual or olfactory cues from herbivore-damaged trees attract insectivorous birds.
• To investigate the independent roles of visual and olfactory signals in bird foraging behavior.

Main Methods:

• Experiments utilized great tits (Parus major) and blue tits (Cyanistes caeruleus).
• Birds were presented with paired Scots pine (Pinus sylvestris) branches, one herbivore-damaged (Diprion pini larvae) and one control.
• Visual cues were isolated by placing branches in transparent cylinders; olfactory cues were isolated using opaque cylinders with mesh lids.

Main Results:

• Birds showed a significant attraction to herbivore-damaged pine branches in both experimental setups.
• Attraction was observed when birds could only see the damaged branches.
• Attraction was also observed when birds could only smell the damaged branches.

Conclusions:

• Both visual and olfactory cues originating from herbivore-damaged plants are sufficient to attract insectivorous birds.
• This suggests birds can utilize distinct sensory pathways to locate food resources indicated by plant damage.