Bird Migration and Movements on
Nexrad Doppler Radar
Western Great Lakes
New Additions- October, 2005
from New Jersey Audubon
Nocturnal migration occurs during spring and fall. Check the calendar here for expected activity
at this latitude. Migration begins about 30-45 minutes after sunset during the early migration
lift-off period called exodus. See quickly what's happening right
now from the US composite reflectivity map
or the Sullivan, Wisc. homepage.
Pick a U.S. Nexrad station at
UCAR or NOAA (no velocity detections)
for reflectivity and velocity maps.
(It is worthwhile to pay the $5/year
for ad-free displays at Weather Underground.)
Milwaukee LaCrosse Green Bay Duluth-Superior
Marquette, MI Gaylord,MI Grand Rapids, MI
Chicago, Ill. Twin Cities, Minn.
U.S. Nexrad and weather front view
Upper Mississippi Valley regional composite
Gulf Coast Radars
From April 15 until early June watch the swarms migrate out of Mexico,
especially over Brownsville, TX. Monitor Houston during the DAY for arrivals
that left Yucatan and the Mexican Gulf coasts the previous night.
Check out this image of daytime migrant arrivals.
Key West Island Hopping Migration
From March through May look each night for
a swarm leaving Cuba and the Florida Keys.
Check out Noel Wamer's archived gifs of these
movements on Badbirdz.
North American and Caribbean tropical radars-
some may not be operating or on-line.
(may not be working)
Check these beginning April 15th after 9 p.m.
They may not be showing current detection views.
Note the date and time on the image.
Tampico- for coastal migration
Cancun- for departures over the Gulf
Recent Nexrad archives
The best frontal analysis
Wisconsin weather forecasts
The Clemson U. Nexrad tutorial
Some Interpretation Basics (click on thumbs)
Nexrad coverage Beam basics Beam basics II Angel anatomy Angel anatomy II Extrapolation
Radar modes Weather vs. birds Radial velocity Nexrad calendar Fall migration Daytime Gulf landfall
Daytime Gulf landfall
migrants ascend to a greater altitude when they recognize water below
Lk. Michigan Why ascend?
An animated GIF of a Peak Night of May Migration
(Thanks to Al Sherkow for hosting this file for several years)
Play the GIF
Analysis of the GIF
Numbers From Nexrad
Migration traffic How many birds Theoretical spacing
rates make up an Angel?
Other Links and References
New links added April 21, 2005
Specific Imagery Examples
☼ A peak May night of migration across eastern North America- note how the composite radar
detections approximate the range map. This is a typical map distribution pattern for many
☼ Migrants and strong storms over Milwaukee and LaCrosse- note how the swarm density is
altered as the birds try to fly higher and around the storm or seem to become grounded. Velocity
imagery shows that some birds turn back south when such storms are encountered.
☼ Fall frontal conditions and transmitter tower/tall building kills- cold front passage will
initiate migration. Birds encounter the cold front, cross it and light rain and fog under a
low ceiling drives them lower without grounding. They are attracted to the light of towers
and buildings and may collide with buildings and the guy wires on certain towers. Flashing
strobe lighting instead of incandescent lights on towers are apparently less attractive to
A tower kill
☼ The Mississippi Valley Effect- compare the densities at LaCrosse with surrounding detections.
☼ Roost rings- these images look like suspicious explosions as birds break roosts after dawn; they
have appeared on conspiracy sites as evidence of alien activity and secret US Gov. projects.
This is from the Great Plains in late July and probably is showing blackbirds leaving roosts
after dawn. The blue map shows waves of bats leaving caves in Texas; note the crescent
shapes of their swarms.
your tax dollars at work
☼ Have you checked your Klystron today? What's inside a Nexrad station?
☼ This looks weird; are we being invaded? - Nexrad Anomalies.
Nexrad and Migration Projects
☼ Moon-watching- birds can be observed flying over the face of the full or near full moon, especially
during peak migration in May and September. This technique requires patience and for the best
results, teamwork. An excellent protocol can be found here. Counts can be correlated with
Nexrad reflectivities. A much better way of recording the data requested by this protocol would
be to mount a video camera on a equatorial telescope mount and track the moon with a lunar
drive speed making sure that the image of the moon fills the field of the camera by 1/2 to 3/4.
October 3, 2005