As a bird banders, I sort of have to keep records regarding the
my catches. About 70% of what I catch in the spring is warblers. I
record the time of capture (more accurately the time or removal from
the net) along with all the official stuff I am supposed to keep track
of.
>From this I can tell you that most migrants migrate in flocks the evidence
beint that I catch birds in waves. I can go one step further many of these
flocks are same sex waves. Wilsons Warbler for example show a two week
difference in male arrivalsbefore female.
I have seen same species flocks of the following:
Swainson's Thrush
Varied Thrush
Warbling Vireo
Black-throated Gray Warbler
Orange-Crowned Warbler
Wilson's Warbler
Yellow Warbler
Yelow-rumped Warbler (no surprise here)
Common Yellowthroat
Rufous-sided Towhee
Black-headed Grosbeak
Northern Oriole

I don't think this should be a particularly surprising revelation. The
neotropical migrants of this group feed in substatial bird parties on their
tropical wintering grounds. They would have similar tastes in stopover
sites and benefit from the safety in numbers advantage of flocking.


>
>
>[accounts of flocking in YRWAs and speculation about whether they migrate
>together snipped]
>
>For those interested in the question, here's a tidbit:
>
>Moore, F. R. (1990) Prothonotary Warblers cross the Gulf of Mexico
>together. Journal of Field Ornithology 61: 285-
>
>As I recall the article, observations made of warblers arriving at a site
>on the U.S. Gulf coast led the observer to conclude that several (3-6?)
>Prothonotaries there had migrated from Venezuela (or wherever) together.
>The evidence was that the PrWas all had some unusual greenish mud smeared
>around their bills and faces. No other migrants arriving that morning
>were stained, and the mud staining was apparently not of local (U.S.)
>origin, so the observer concluded that the PrWas had foraged together,
>migrated together, and arrived together. I may be corrupting some details
>- I read it when it came out, which was quite a while ago. As I
>recall, the account was more convincing than my summary here. Dennis, do you
>have it on the bookshelf? The article should mention if there is other
>evidence for passerines migrating at night in conspecific flocks.
>
>Chris Hill
>Seattle, WA
>cehill at u.washington.edu
>
>
>
>
>
>

--
********************************
* Mike Patterson, Astoria, OR * "Time flies like an arrow;
* mpatters at ednet1.osl.or.gov * fruit flies like a banana."
******************************** - Groucho Marx