The white collar apparently is not much of an indicator of the subspecies, even though at one time it was thought to be.
A white collar at the base of the neck below the dark "neck sock" is a conspicuous feature of some Canada and Cackling Geese. It tends to be more common in the smaller subspecies and is most conspicuous in the dark-breasted ones, since it contrasts more with a dark breast than with a pale one. A survey by Marquardt (1961) of presumed B. c. parvipes and B. h. hutchinsii in the southern Central flyway (Colorado, Oklahoma, and Texas) found that nearly 50% of adults and 25% of immatures had white collars, even though Palmer (1976) and Mowbray et al (2002) report that these two subspecies seldom show a white collar. Even in B. h. leucopareia, the Aleutian Cackling Goose that is characterized by a broad white collar, Palmer (1976) reports a survey of nesting birds on Buldir Island, Alaska in which 47 birds had a white collar, 9 had no white collar, and 8 had breasts so pale that a white collar was not discernible. Perhaps with more data the presence of a white collar will have some value as a weak indicator of one subspecies over another, but at this point it seems nearly worthless.
--- In CALBIRDS@yahoogroups.com, "woodshots" <woodshots@...> wrote:
> This afternoon on a Fresno Audubon field trip to the Parkfield area we ended the trip around Cholame and at a small irrigation reservoir south of town on the north side of Starkey just west of Truesdale we found 4 CACKLING GEESE feeding on the west bank. 3 of them had broad white collars at the base of the neck and two had very dark tan breasts, one of which had no white collar, so your guess is welcome as to which subspecies these might be. There were also two female HOODED MERGANSERS nearby. Gary Woods-Fresno