Relative competitive ability changes with competitor density: evidence from feeding blackbirds

Area of Science:

• Behavioral Ecology
• Population Dynamics

Background:

• Understanding how individual competitive ability varies with competitor density is crucial for ecological models.
• Few studies have investigated this variation in systems with interference competition.

Purpose of the Study:

• To measure individual variation in competitive ability in wild wintering blackbirds (Turdus merula).
• To assess how feeding rates change with competitor density and individual traits.

Main Methods:

• Experimental patches were used to measure the feeding rate of single birds.
• The decline in feeding rate was recorded in the presence of varying numbers of competitors.

Main Results:

• Significant individual variation was found in both baseline feeding rates and the reduction in feeding rates when competitors were present.
• Birds with higher absolute feeding rates did not necessarily show smaller declines in feeding rate with increased competition.
• The relative competitive ranking of individual birds was highly dependent on competitor density.

Conclusions:

• Individual competitive ability is not static and is strongly influenced by competitor density.
• These findings have significant implications for predicting competitor distributions in ecological systems and refining ideal free distribution models.