Quantifying purported competition with individual- and population-level metrics.

Area of Science:

• Ecology
• Conservation Biology
• Behavioral Ecology

Background:

• Interspecific competition can impact population dynamics, potentially affecting endangered species.
• Red-bellied Woodpeckers (Melanerpes carolinus) and Red-cockaded Woodpeckers (Picoides borealis) are thought to compete for limited cavity resources in pine trees.

Purpose of the Study:

• To investigate if behavioral competition between Red-bellied Woodpeckers and Red-cockaded Woodpeckers affects Red-cockaded Woodpecker population fitness.
• To determine if individual-level interactions translate to population-level consequences for an endangered species.

Main Methods:

• Conducted a 4-year field study in the Apalachicola National Forest, Florida, comparing stable and declining Red-cockaded Woodpecker populations.
• Implemented Red-bellied Woodpecker removal experiments in specific territories to assess impacts on Red-cockaded Woodpeckers.

Main Results:

• Red-cockaded Woodpecker group size, nesting success, and territory retention decreased after Red-bellied Woodpecker removal.
• Removal may have increased Red-bellied Woodpecker immigration, negatively impacting Red-cockaded Woodpeckers, especially in declining populations.
• Population persistence in the Wakulla District was linked to high female turnover, exacerbated by Red-bellied Woodpecker removal.

Conclusions:

• Observed competitive interactions at the individual level do not always predict population-level outcomes.
• Removing a perceived competitor species can unexpectedly harm the species of conservation concern.
• Conservation strategies should consider complex ecological interactions beyond simple competition.