I have been watching the weather radar more closely this spring in hopes
of seeing when I should make a point of being out in the morning to look
for migrants.  I have made little progress learning about landbird
migration, because this spring there have been no good migration days to
compare to the radar.  However, four or five times I have seen a blob of
echoes moving during daylight between the Chesapeake Bay somewhere near
Easton MD to Delaware Bay roughly at Slaughter Beach DE.  Since I don't
know the Chesapeake nearly as well as I know Delaware, I am more sure of
the destination than I am of the origin of these birds.  The blob moves
at about the right speed to be birds, and every time that I have seen it
the tide was dropping toward low on the Delaware side.  If I have the
right origin of the blob, the tide is nearer high on the Chesapeake
side.  The combination of tide levels supports my guess that the echoes
are coming from a flock of shore-feeding birds of some type.

Anyone who wants to look at the radar to see if I am just fooling myself
can go to
<http://www.rap.ucar.edu/weather/radar/>, choose 01 June for the date,
1900 UTC for the ending time, and two hours for the duration, and then
click "DOX" [the Dover radar, which is actually near Ellendale] on the
map.  1900 UTC is 3PM Eastern time, and the archive is kept 6 days, so
after about June 7 this sequence will no longer be available.

I have several questions someone might be able to answer for me.  First,
can anyone who knows Maryland look at these images and give me a better
reading on where the birds are coming from?  Second, is anyone already
aware of a movement of this sort between the Bays, either by shorebirds
or by gulls?  I know about movements from Delaware Bay a short distance
inland to impoundments and open fields at local high tide but I have
never heard of birds moving all the way between the two Bays.  Third,
does anyone know of movement back, or is this a one-way passage?

I have not been able to tell from the radar whether or not birds move
back to the Chesapeake from Delaware Bay when the tides reverse.  I have
seen signs of a broad line of movement back, but I am not sure that what
I see is definitely nonmeteorological  I have twice seen a line of
echoes moving backwards but am afraid I may just have seen some effect
of the afternoon sea breeze.  I'll know better if I see the same pattern
at a different time of day.

I am posting this to both DE-birds and MD-Osprey since it is relevant to
both states.

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