|Greater White-fronted Goose. Lindo Lake, California. February 9, 2014. Greg Gillson.|
Greater White-fronted Geese that nest in Alaska winter in two primary areas (see this explanation and map by David Sibley). One group winters in the Klamath Basin and northern Central Valley of California, with others continuing to northwestern Mexico (coastal Sonora). A second group winters in central Mexico.
Away from the primary wintering areas it is not unusual for lone geese or assumed family groups to settle in with other wild or tame geese, such as a local city park. When you are a stranger, it is safer to behave as the locals. Thus, these individuals that turn up at city parks soon behave just like the tame geese which they have joined.
From looking at eBird data for the Lindo Lake hotspot, it appears this individual bird has remained year-round here for at least 2 years without migrating to Alaska in spring. Good for its personal survival, but not adding anything to its species gene pool!
Retiring to San Diego. Could you blame it?