Australasian darter
... that the plumage of the Australasian darter absorbs water to reduce the bird's buoyancy and allow it to swim submerged?
... that the plumage of the <b id="mwGg"><a href="./Australasian_darter" id="mwGw" rel="mw:WikiLink" title="Australasian darter">Australasian darter</a></b> <i id="mwHA">(pictured)</i> absorbs water to reduce the bird's buoyancy and allow it to swim submerged?