Why diving ducks are not as closely related to dabbling ducks as they look

Nature · Published 3 October 2026 Swipe more like this →

In short: Diving ducks and dabbling ducks share a similar appearance, but this is a classic case of convergent evolution. Despite their outward resemblance, molecular data reveals they are quite distant relatives. These birds have evolved specialized physical traits, like rear-positioned legs, that make them masters of the water but clumsy on land.

The diving ducks, or Aythyini, represent a distinct tribe within the Anatidae family. While they are often compared to dabbling ducks, their internal anatomy—specifically the structure of their trachea—highlights significant differences. Genetic analysis using mtDNA cytochrome b and NADH dehydrogenase subunit 2 confirms that these two groups are not as closely linked as their similar shapes might suggest. Instead, their shared characteristics are the result of independent evolutionary paths converging on similar solutions for survival.

These birds are built for life beneath the surface. Their legs are set further back on their bodies, an adaptation that provides powerful propulsion underwater but makes walking on solid ground a difficult task. Because of this, they are primarily found in fresh water or estuaries, though some species, like the greater scaup, move into marine environments during the winter. Their flight is equally specialized; they possess broad, blunt-tipped wings that necessitate a rapid, energetic wing-beat frequency to achieve lift, often making takeoff a laborious process compared to other waterfowl.

Taxonomy within this group remains a subject of investigation. The marbled duck, for instance, appears to have diverged before the split between dabbling and diving ducks. Similarly, the pink-headed duck, which is likely extinct, has been identified through DNA analysis as the earliest diverging member of the pochard lineage. Other groups, such as the seaducks of the Merginae subfamily, are often colloquially grouped with diving ducks due to their feeding habits, yet they belong to an entirely separate evolutionary branch. This complexity underscores the difficulty of classifying these birds based on behavior alone, as even within the Aythyini, some species like the Netta are reluctant to dive, preferring to feed in the manner of their dabbling cousins.

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