Functional responses of the rough-legged buzzard in a multi-prey system

Area of Science:

• Ecology
• Zoology
• Behavioral Ecology

Background:

• Predator-prey dynamics are fundamental to ecological systems.
• Functional response theory models individual predator foraging behavior.
• Previous studies often used population-averaged data for free-ranging predators.

Purpose of the Study:

• To investigate the functional responses of rough-legged buzzards (Buteo lagopus) to varying rodent densities in subarctic Sweden.
• To analyze how avian predators utilize different rodent prey species based on their abundance and characteristics.
• To understand the implications of prey selection and switching behavior in predator-prey interactions.

Main Methods:

• Utilized a novel approach analyzing breeding pairs of rough-legged buzzards as the sampling unit.
• Assessed functional responses to Norwegian lemmings, grey-sided voles, and field voles.
• Examined diet composition relative to prey abundance and identified prey switching patterns.

Main Results:

• Rough-legged buzzards showed functional responses to all three rodent species, but not in proportion to their abundance.
• A type II functional response was observed for Norwegian lemmings, while a type III response was noted for grey-sided voles.
• Diet composition showed less variation than relative prey abundance, indicating negative switching, particularly with lemmings at low densities.

Conclusions:

• Differences in functional response curves (type II for lemmings, type III for voles) are attributed to habitat use, anti-predator behavior, and size-dependent vulnerability.
• Negative switching suggests specialized predation strategies by rough-legged buzzards.
• Lemmings and voles should be studied separately in future research to accurately model predation's role in this ecosystem.