{Mike, My idea of Black Swift nesting habitat in the Cascades is that
portion of the range north of the "Wallowa Linement," ie. Snoqualmie Pass.
>From there north an abrupt change in physiography of the North Cascades is
apparent. Local relief becomes more pronounced, the valleys overdeepened
by glaciation and its wet! I've noted a morning exodus of Black Swifts
from the following valleys in June and July in addition to the ones you
mentioned:
1-at Alpental north of Snoqualmie Pass
2-at Gold Creek north of Hyak
3-at Stehekin at the west end of Lake Chelan

I would guess all these valleys support breeding Black Swifts.

Andy Stepniewski
Wapato, WA