The Greatest Bird Migration on Record! Weather Played a Major Role.

The greatest southward bird migration on record in the U.S. occurred on Wednesday night, and weather played a major role.

Today, the key tool for tracking bird migration is weather radar.   And there is a wonderful website...BirdCast.... that provides real-time, radar-based estimates of bird migration.

On Wednesday night at 10 PM EST, the BirdCast estimated migration was an incredible 1.25 BILLION birds, the largest number ever observed (radar only goes back to the mid-90s.     

The center of the migration was over the southeast U.S. (see map above).  

But why there? 

 It turns out that the weather played an important role.

Seasonally, migration peaks from approximately mid-September to mid-October over the southeast U.S., according to BirdCast.   So we are in the season.  

But there was a major weather assist as well.   A strong front had just moved south, with a huge high-pressure area to its north (see  surface weather map below)

Just a pattern with high pressure to the north and lower pressure to the south produces strong northerly (from the north) winds in the lower atmosphere...a boon to birds heading south for the winter.   

Below are the forecast winds for 8 PM EST on Wednesday night at around 5000 ft (850 hPa pressure).  Winds were from the northeast to the southwest.  Blowing in the direction the birds were headed.

According to many sources I reviewed, birds like rising pressure without precipitation.

Exactly the conditions observed on Wednesday evening.

Let me show you a sample radar image from Fr. Campbell, KY, just after midnight.  

The sky was filled with intense bird echoes.

Finally, what about bird migration over the Northwest,  you ask?  At 7:50 PM Saturday night, the Northwest migration was a shadow of the bird movement of the eastern US, with our wet, stormy weather not a positive for our bird friends.