The great grey owl's enormous facial disc functions as a sound collector, and its hearing is acute enough to pinpoint a vole tunnelling under a snowpack. The bird perches or hovers, fixes the source, then drops feet-first, punching through the crust with the legs extended and the wings held back.
The technique, called snow plunging, works through substantial depths; captures have been documented through snow deep enough to bury the owl on impact. It also requires the crust to be penetrable, so a hard ice layer after a thaw and refreeze can lock the prey away and trigger movements to other areas or, in bad years, starvation.
Size is the most common misconception here. The great grey owl is the tallest North American owl by length and has a wingspan near 1.4 metres, but it is mostly feather. Body weight of roughly one to 1.7 kilograms is well below that of a great horned owl or snowy owl.