Dennis, et al.,

re Black-capped Chickadees: it seems to me the black-capped chickadees
here may represent a post Pleistocene expansion. Virtually the entire
area connecting the west coast pops with the core to the east was under a
mile of ice until ca 15000 BP. Also note that Black-cappeds are rare of
absent on Vancouver I, San Juan Islands, even somewhat scarce on Vashon,
as if they had not yet had time to invade those chestnut-backed
strongholds. Also note that the black-capped reaches its southern limit
in extreme northern California, around Mt. Shasta on the east and
Humboldt Bay on the west. Could that have to do with the lack of eruptions?

Gene Hunn.

On Mon, 6 Jun 1994, Dennis Paulson wrote:

> >On the discussion of boreal chickadees, why don't we encounter the
> >phenomena of boreal chickadee invasions such as occur in eastern North
> >America? Is the potential source of birds too small, the ecology of
> >western forests different, or has the notion of invasions been
> >overblown?
> >
> >Jerry Tangren
>
> Jerry posed an interesting question, to which I'd like to add what I
> consider an even more interesting one--why don't we have irruptions of
> BLACK-CAPPED chickadees, which are well-known in the east? This bird is
> very common, and we'd surely know of such movements. Mountain chickadees
> move downslope a bit in winter, appearing from time to time in western WA,
> but I haven't heard of black-capped movements either E of W of the
> Cascades. Anybody ever seen one?
>
> Of course the forests in which black-capped chickadees live here are indeed
> rather different from the deciduous forests of the Northeast. Black-capped
> here is not the climax-forest chickadee, as it is in the East, and its
> populations may be a lot smaller and not subject to the same cycles that
> might occur in the extensive eastern forests.
>
> By the way, for a great book, read Susan Smith's "The Black-capped Chickadee."
>
> Dennis Paulson
>
>
>