Grainger uses watercolor sketches like the one above to preserve and note the precise coloring of the non-feather elements of a bird. The colors on the feet and bill (unlike those on feathers) degrade quickly with time, so must be recorded from a live or freshly killed specimen.
Three Mallards uses a fully connected infrastructure of heat-treated steel for support. This is somewhat of a departure from his earlier works, where the connecting steel feathers will usually terminate into their respective birds with nuts and bolts.
Click here to see a high-resolution PDF document of how the sculpture was made.