Ohio's first Ross's goose was verified in 1982.  Since then white Chen
geese have demonstrably increased in numbers, even as migrants here in
Ohio, which is well east of its migratory path. I am assuming the snow
geese we nearly always see are C.c caerulescens, the "lesser snow goose."
        For years, Ross's reports required an OK from the Ohio Bird Records
Committee in order to enter the official record. As the years passed,
local observers learned how to distinguish them, and increasing reports
of Ross's were more and more often accepted as records; the species
passed the threshold of numbers of verified occurrences that set it
aside as a Review Species, and folks who wanted a record to count no
longer had to write their sightings up for review.
        In the years since that time it is worth wondering if that decision was
premature. I am seeing lots of birds, and excellent photos of birds,
such as the ones Matt Valencic shared yesterday on this forum, that look
like snow X Ross's hybrids, with intermediate characters.
        It's common knowledge that the 'white geese' of the Nearctic are
exploding in population. Some states now allow them to be hunted without
any bag limits, regarding them as nuisances. The nesting areas of these
geese have grown in size in recent decades, and one wonders if breeding
populations have moved close enough to allow more hybridization.
Presumably eons ago these two species branched out of a primeval white
goose form; is evolution reversing its course to some extent because of
convergences of habitats up north? Several times in the past few years I
and others have seen gatherings of white geese that seemed to come in
three discernible sizes: snow, Ross's, and Snoss's. Tom Bartlett
recently shared some photos with me of flocks of geese passing over
Kelley's Island that seemed to show just this disparity.
        The hybrids usually show blurring of the characteristics we used to
rely on to tell snows from Ross's. Closer looks are called for. The
obvious difference in sizes, for example, doesn't seem as clear as it
once did. In 1976 Bellrose gave the following average lengths:  lesser
snow 29 in, Ross's 25 in, and mallard 24.7.  Thus, a 'Ross's' that is
obviously larger than a mallard is probably not. The same goes for
bill/head structure; a small white goose whose bill and join with the
skull is not 'cute' enough is probably a hybrid. A bird that shows a
little of each distribution of dark on the bill--such as black "lips"
like the snow's *and* duskiness at the base like Ross's--is argubly not
either in its pure form; look at the Ashtabula bird. Sibley (2000, p.
79) illustrates this well.
        I've been as guilty as anyone in confidently calling out a Ross's as I
scanned a flock of geese on a pond from a speeding car.
Things aren't so easy anymore. There was an instructive page of photos
of geese heads on page 64 of The Ohio Cardinal (Fall 2007); they are of
known-identity museum specimens collected decades ago, lying on a
centimeter grid; I can send them to folks who are curious, but Sibley's
paintings show the same thing.  They also make me wonder if every
cackling goose we call is really a cackling goose or a locally rare
Canada goose subspecies. Worth considering.  Any thoughts from others?
Bill Whan
Columbus

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