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Q32 - Seabird Foraging and Niche Segregation

Theoretical 2 Real exam question - full text reproduced under IBO's CC BY-NC-SA 4.0 license
Foraging & Anti-Predator Behavior

Seabirds spend much of their lives in the open ocean foraging but, during breeding, they congregate on remote islands or cliffs to nest. Figure A shows the foraging distribution of four species of seabirds. Relative proportions of stable isotopes (15N and 13C) were determined from blood collected from breeding individuals (Figure B).

Species Max diving depth (m)
Atlantic Puffin (Fratercula arctica) (n=3) 60
Razorbill (Alca torda) (n=5) 120
Common Murre (Uria aalge) (n=5) 180+
Thick-billed Murre (Uria lomvia) (n=7) 180+

Figure A: Foraging distribution map of four seabird species

Figure B: Stable isotope ratios (δ15N vs δ13C) for the four species

Based on the figures above, state if the following statements are true or false.

Q32.1. The foraging patterns indicate evidence of niche segregation in Atlantic Puffins and Razorbills.
Q32.2. Common Murres and Thick-billed Murres have similar diets.
Q32.3. Atlantic Puffins mostly forage in near-shore areas (close to the coast).
Q32.4. Razorbills and Common Murres have similar diets.
Q32.5. Thick-billed murres and razorbills have considerable foraging overlap.
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Question reproduced from IBO 2023, Theoretical Paper 2, licensed under CC BY-NC-SA 4.0 - attributed to the International Biology Olympiad. Open the full exam PDF