Monday, April 27, 2009

Friday Night Migration

Posted by Kirk
I noticed over on the Minnesota Birdnerd blog that Roger captured a great still image of migration picked up by NEXTRAD radar on Friday night. It was such an impressive display that I knew I needed to create another radar loop of the migration. It took about an hour to build this loop by hand.

(Please allow a little time for it to load. The animation image is very large)

There is a little bit of a shake to the image because of the process I used. It would take a long time to get rid of it and would involve going through the 90 or so images that make up the animation by hand and modifying them.

There are some fascinating things to see in the loop. Click on it to open in a new window and view in a slightly larger size.

(sometimes the image does not appear here or fails to animate. Follow this link to see it in motion.

1) The most obvious thing to see is that most birds choose to migrate at night. The loop starts at 0002 UTC which corresponds to 7:00 Central Daylight Time. The loop ends about midnight CDT. You can see the birds take off after sunset and you can watch he wave of take-offs start in the east and move west. They start first down by Georgia.

2) Look at the explosion of birds taking off from Louisiana at sunset.

3) Notice the birds tend to stick to land. One exception is that migration has now reached the Great Lakes. Look at Lake Michigan, Lake Huron and Lake Erie. Some migrants seem to be making crossings there. Birds don't seem too keen about crossing Lake Superior except for near Duluth where the crossing is short.

4) Look carefully at the coast of Texas. It is thick with birds early in the evening but by the end of the loop all the birds have pushed north and the coast seems pretty quiet.