Perhaps the most likely explanation, and the one currently favoured, is that it is a hybrid between hutchinsii and parvipes. There is apparently a fair amount of hybridisation where the two taxa overlap.
- Dusky breast
- Short stubby bill (though longer than the average, it seems to fall within the normal variation)
- Small size, maybe 60%-70% of the size on nearby Canadas
- Buffy throat patch.
Distribution of various subspecies of Cackling and Canada Goose. From the Sibley Guides website