Explain how the concept of resource partitioning allows multiple species of closely related birds to coexist within the same woodland habitat.

IB DP Biology Standard Level (2023 syllabus) — B4.2 Ecological niches · Explain · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

In a temperate woodland, several species of warbler feed on insects found in the same trees. Observations show that each species forages at a characteristic height within the canopy and uses a distinct foraging behaviour.

Model answer (4 marks)

Resource partitioning means that species divide up available resources so that each species exploits a different portion of those resources.
Each warbler species occupies a distinct ecological niche, differing in foraging height and/or behaviour, which reduces niche overlap.
Reduced niche overlap decreases inter‑specific competition between the warbler species.
With inter‑specific competition sufficiently reduced, competitive exclusion does not occur and the species coexist stably in the same habitat.

Examiner tips

Use the word ‘resource partitioning’ early to show understanding of the concept.
Show the link between niche differentiation and reduced competition.
Mention competitive exclusion as the outcome of reduced competition.
Keep each point brief and to the point to fit the 4‑mark limit.

Common mistakes

Confusing resource partitioning with resource competition; not explaining how niches differ.
Failing to mention competitive exclusion or the stability of coexistence.
Writing overly long explanations that exceed the 4‑mark scope.

Mark scheme (4 marks)

Resource partitioning means that species divide up available resources so that each species exploits a different portion of those resources
Each warbler species occupies a distinct ecological niche, differing in foraging height and/or behaviour, reducing niche overlap
Reduced niche overlap decreases interspecific competition between the warbler species
With interspecific competition sufficiently reduced, competitive exclusion does not occur and species coexist stably in the same habitat

Key terms in this question

resource partitioning