Question

fatter sociable weaver birds spend more time foraging where they are vulnerable to predation, are more attractive to predators, and are less likely to escape an attack. conversely, thin birds risk starvation. therefore, sociable weaver of an intermediate weight have a selective advantage. this is an example of ______ selection.

frequent
directional
disruptive
stabilizing
mutational

Explanation:

Stabilizing selection favors intermediate phenotypes. In this case, intermediate - weight sociable weaver birds have a selective advantage over both very fat (vulnerable to predation) and very thin (risk of starvation) birds. Directional selection would favor one extreme phenotype, disruptive selection would favor both extremes, and "frequent" and "mutational" are not standard terms for this type of selection.

Answer:

stabilizing