------------------------------------------------------------------------------
FORWARDED FROM: Gates, Bryan
FROM: Gates, Bryan
DATE: 95/04/21 15:39
TO: owner-tweeters at u.washington.edu

CC:
SUBJECT: Yellow-rumped Warblers
PRIORITY:
ATTACHMENTS:
------------------------------------------------------------------------------
Dennis says, about YRWA:

>This species seems so often to be seen in isolated flocks (as Mike Smith
>reported; I have yet to see any in my neighborhood) that I wonder if
>perhaps they *migrate* in flocks, something I hadn't thought was
>characteristic of any warbler.

I must admit that it has not occurred to me that YRWAs do _not_ migrate in
flocks, since that is the way they show up here on S. Vancouver Island
each spring. Although there has been a lone bird in my yard (Garry Oak
forest) for the past two days, and other reports of lone birds do
come in to the Victoria Rare Bird Alert, normally I can expect to see
(and hear of) flocks of 5 to 20 moving loosely as a group through the trees,
their chip notes presumably keeping them together. It could be that these
are foraging flocks that have met for the day, with the birds moving off
individually at night, perhaps to join other flocks of mixed passerine
migrants. But, for some reason, that doesn't seem logical to me.

As for our other warbler species, group movements do not seem to occur...
perhaps 2 or 3 Orange-crowns, Townsends, Black-throated Grays, etc, and
perhaps a loose association of these species, but always small numbers.

Interesting thought, Dennis. Does anyone know of literature on why warblers
in general do not migrate as flocks?...or why YRWAs are (or are not)
different in this regard? Then again, who knows what happens at night?
Perhaps those radar blips are pure flocks of MacGillivray's, or Yellows,
or...? Those with exceptional ears and who pretent to sleep under the stars,
tend to claim that they hear groups of mixed species passing over.

Anyone else with observations?

Bryan Gates, Victoria
bgates at assessment.env.gov.bc.ca