You certainly can see the movement even in precipition mode.  See
Gauthreaux and Belser, Birding 35 (Dec 2003), 616.  The problem is
turning birds in the air into birds on the ground, perhaps especially as
far from any of the radar sites as I am in Newark. I could see major
differences in the radar comparing pictures just before dawn to those
just after, even in precipitation mode.  The amount of the difference
even made sense when compared to the weather south of us, and the
difference is less now that the bulk of landbird migration is over.  You
can also filter for velocity on the Doppler plots, but not really fast
enough to decide you have to get out that morning (I haven't explored
getting software and a subscription to the corresponding archive site
yet).  The images also make sense when compared to topography. The birds
avoid large bodies of water, and echoes bunch up at dawn along the shore
of Delaware Bay.

I am sure that the movement I saw from Chesapeake Bay to Delaware Bay is
real.  I can't be sure that I have seen the reverse.  I can't use the
velocity plots to verify this particular movement because it is almost
perpendicular to the direction to the radar, and only the movement
toward or away from the radar shows.  That is why I didn't mention the
velocity plots in what I said about the shorebird/Gull movement.
 However, by comparing with bird echoes I can verify using velocity
plots and comparing the movement of the echo to the wind direction on
the Doppler plots, I am happy with the echoes being birds of some sort.

Joe McDaniel wrote:

>You have to make sure you are looking at the non-precipitation mode data. I think it is called something like "clear mode". The "precipitation mode" is tuned to look for rain/hail/etc. while the "clear mode" will see things like birds, cicadas, insects, and dust.  A few years ago Cornell did a study using the weather radar to track migration. It was interesting but whether anything ever came from it????
>
>Best,
>
>Joe
>
>
>

--
Maurice Barnhill
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Department of Physics and Astronomy
University of Delaware
Newark, DE 19716