Egg Shell and Membrane Removal

After the hatch of their first chick, it is very common for adult loons to remove the membrane from the first hatched egg and any attached large pieces of eggshell from their nest. This behavior has been widely documented here in New Hampshire, both on LPC's Live Loon Cams (see video below) and by wildlife photographers, as well as by biologists in the field. Why do loons remove shells and membranes from their nests when many other bird species do not perform this behavior?