Radar and bird migration

Radar image from Lake Charles, LA showing birds moving over the Gulf of Mexico towards land in April, 1999.

New technology moves science forward.  Sometimes technology developed for the space program or military will have unanticipated uses elsewhere.  Research on bird migration is a fascinating example of this type of technology transfer. Using weather radar to track bird migration has little to do with hummingbirds specifically – but as I read about migration – I found this example of applying weather technology to biological science to be a great story!

Since World War II, birds and other living things traveling en masse have appeared on military and weather radar.  These were considered a nuisance to be filtered out.  Because migrating birds appeared as wispy patterns on the radar screens at night and disappeared at dawn they were termed “Angels” by early technicians.  Before biologists discovered this tool – the only visual analysis of bird migration at night had been watching the full moon to observe and count nocturnal migrants.

NEXRAD stations cover the United States and the data is available to anyone with a computer.

 Today, people still watch nocturnal migrants travel across full moons.  But in the last few decades scientists have figured out how migrating birds appear on a national network of Doppler Radar stations known as NEXRAD (NEXt generation RADar).  Radar can detect precipitation, particulate matter, insects, bats – any object in the atmosphere.  The velocity and direction of movement of these objects can also be detected.

During peak migration, birds will "exodus" 30-45 minutes after sunset leading to a spectacular radar image.

  Expert interpreters can glean lots of information from looking at radar images of bird migration. Studies of radar are becoming another tool for ornithological study. Knowing where these birds stop over, where they depart from and the path of their travel is of interest to citizen scientists as well as the experts and the availability of NEXRAD data on-line makes this a useful tool for the serious birder.

The more I read about bird migration the more amazed I am.  Birds as tiny as the hummingbird are thought to fly over the Gulf of Mexico – that’s 1000 km non-stop!  But, do all Ruby-throated Hummingbirds migrate across the Gulf – or do some skirt the edges as they travel from Mexico and Central America to the coast of the Southern United States (and back)?  As I read about Ruby-throated Hummingbirds I am fascinated by all the unanswered questions we have about this phenomenon called bird migration.  

We know when they arrive and that the males arrive first but there are still many unanswered questions about Ruby-throated hummingbird migration.

Preparing for the journey requires fat to be stored, feathers to be molted and flight muscles to be strengthened.  Some bird species are nocturnal others migrate by day.  Some species flap their wings continuously as they fly others flap and bound and still others flap and glide.   Cloud cover, wind speed and direction are vital considerations as different species decide when to depart and at which altitude and speed to fly.  And then there are the hazards they face along the way.  Beyond huge bodies of water like the Gulf and the Great Lakes there are weather hazards, collisions with buildings and cars, disappearing habitat and predation.   

For a good overview of the migration of the Ruby-throated hummingbird visit this page from Operation RubyThroat:

http://www.rubythroat.org/RTHUMigrationMain.html