Bird Migration and Movements on

Nexrad Doppler Radar

 From Wisconsin

and the

Western Great Lakes







New Additions- October, 2005



A May Lake crossing to Michigan showing first land fallout


A Green Bay Velocity Loop Showing Birds Over Lake Michigan Both Returning to the Western Shore and Heading East to Michigan


The Spring, 2005 Season Summary


The September Madison Towerkills







Nexrad and Bird Conservation




An Introduction to Radar Ornithology


Why Nexrad and birds?

from New Jersey Audubon




Quick Links


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)


or visit


Weather Underground

for reflectivity and velocity maps.

(It is worthwhile to pay the $5/year

for ad-free displays at Weather Underground.)




Local Sites


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.


Mexican Radars

(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


More Links

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

velocity  backdraw



Migrant Ascension-

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 

         Neotropical species.       

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.





Nexrad Trivia,

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.





  Stop again



 John Idzikowski

  October 3, 2005