How does convergent evolution explain the similarity between diving petrels and auks?

Convergent evolution explains the similarity between diving petrels and auks as a classic example of unrelated species developing similar physical traits and habits to adapt to comparable ecological niches.1

Although diving petrels belong to the order Procellariiformes and auks belong to the order Charadriiformes, both groups have evolved to become specialized for life in their respective environments. Because they occupy similar roles as small, diving seabirds, they have independently developed comparable features, including:12

• Body Morphology: Both are short-winged and heavy-bodied, with a similar black-and-white appearance.12
• Locomotion: Both groups use their wings for propulsion while swimming underwater.13

This resemblance is not due to a close evolutionary relationship, but rather the result of independent evolutionary paths leading to similar functional adaptations for survival in the water.12