Dominic Sherony shares thoughts on the American Bittern
You will notice in this photograph of American Bittern that the bird is landing and has raised its lesser coverts and alula. These feathers are not being blown up by the wind but were intentionally raised.
The bird is using its lesser coverts to maintain lift while it lowers its primaries and secondaries to create drag, thus slowing itself down and allowing for a “soft” touchdown. This is the same landing strategy used in large commercial jet airplanes.