Hi Tweeters

Solitary Vireos' arrival are in fact late March to mid-April in Vancouver
BC also (the 12-year average in Vancouver is 4.13), and to add to what
Bryan Gates pointed out regarding the influence of observer coverage, I'd
suggest that *some* (and I stress that there are not many, but some) *very*
early birds (of many or most migrants) may be mis-identifications of
wintering birds in transitional, non-illustrated plumages, or that they may
be overwintering birds in locations where first arrivals show up also, and
that first observations of a species long past (10--14 days or more) its
average arrival date is more likely due to a lack of observers hitting
locations where the species is likely to show up first tahn an actual late
arrival, though it can happen.

Most species that I've been able to figure out usually have somewhat narrow
windows (10 days is wide) for first arrivals; one major exception is Vaux's
Swift, whose first arrival can be anywhere from late March to late April,
an extraordinarily wide arrival window. Part of the problem with very early
first arrival VASW, though, may be found in the possible confusion with
--of all things-- Violet-green Swallows doing their 'stiff-wing' display,
in which a swallow will flutter and glide on stiffly-extended wings for up
to a minute or more (but usually only 10--30 seconds) looking very much
like a swift in silhouette high against grey March/early April skies. They
still fool me, and the only way I know which is which under those
circumstances is that the swallow stops being a swift while the swift
doesn't :-)

Michael Price
Vancouveer BC Canada
michael_price at mindlink.bc.ca