For your interest on stained geese:

>From The British Columbia Waterfowl Society's publication "Marshnotes" Fall
1993:

Wrangle Island Snow Geese by Sean Boyd

"Bulrush rhizomes are a key component in the diet of Snow Geese during fall
and winter. The geese forage for rhizoms by grubbing in the mud to depths of
more than 20cm. The mud contains high levels of iron oxide so the
Fraser/Skagit geese develope characteristic rusty-coloured faces. California
geese feed above ground on rice and corn so they retain white faces. Russian
biologists use the intensity of facial stain to deteremine in which area an
individual goose has spent the winter"


I hope that sheds some light on your interest in stained geese.

~ Cameron Eckert