Red-breasted Nuthatch, Sitta canadensis

Family Paridae, on the trunk of a redwood in urban Mountain View.

Normally seen only briefly in mid-autumn (ie, during migration), in 2008 two of these nuthatches
showed up in late October and remained for an extended period: two were seen regularly
visiting a seed block through December; a single individual remained in the area until mid-March.

Might this behavioral shift suggest that due to global warming the species is not migrating as far south as it once did?