>
> Steve Mlodinow reported on the WA Birdbox that several rumored splits by
> the AOU are, in fact, imminent. I was wondering about several of these:
> 1) Bicknell's vs. Grey-cheeked Thrush - how specific are their ranges and
> do they overlap? 2) Where do Rufous-sided Towhees become Spotted Towhees?
> and 3) What is the "north-south" split of Sharp-tailed Sparrow?

As far as I know, the ranges of the Grey-cheek and Bicknell's Thrush do
not overlap. Bicknell's breeds in the mountains of s. Quebec and New
England, you could find them in the Catskills, Adirondacks, Green
Mountains and White Mountains. The Grey-cheek is boreal, and gets nearest
to the Bicknells along the north shore of the St. Lawrence River.
I am unsure about the towhees, but at least in Canada it appears to
happen quite far east in Saskatchewan. As has been pointed out, the
Sharp-tailed Sparrow story is much more complex. The northern
Sharp-tailed Sparrow includes the populations from the Praries and Great
Plains, the ones along the shores of Hudson's and James' Bay and the ones
on the Gaspe peninsula and the Maritimes. This last population overlaps
with the southern Sharp-tailed in southern Maine. The Southern Sharp-tail
breeds along th Atlantic coast from s. Maine to the Delmarva peninsula.
There are other birds which show this distribution pattern of having a
population along the Atlantic coast and another in the interior, i.e.
Willet and Piping Plover. It would be interesting to find out if these
species also show as large a difference between their populations as do
the Sharp-tailed Sparrows.
I find it interesting that the AOU has chosen
to split this one since the paper that published the findings (Rising &
Avise 1993, Auk 110:844-856) recomended that two subspecies be
recognized. I know for a fact that this was an idea of the junior author,
the senior author wanted to recomend a full split. By reading the paper,
it sure is convincing that these two buggers are different species. With
Greenlaw's behavioural data, these two types differ in three ways:
morphology, genetics and behaviour. What more does one need?

Al Jaramillo
jaramill at sfu.ca
Vancouver, B.C.