Monday, March 16, 2009

Massive Migration

Posted by Kirk
Roger Everhart, a.k.a. Minnesota Birdnerd has been posting some fantastic static shots of bird migration picked up with doppler radar. I've read some about this phenomenon in the past and it has always fascinated me. Basically, the millions of migrating birds show up as clutter on the radar and you can see bloom of birds taking off in the evening as they begin migrating at night. They migrate at night as it is cooler out and they can avoid predators. Also, many birds use stars and the moon as navigational aids.

I checked out the live national radar loop tonight and there was an incredible bloom of migrating birds taking off just after sunset. I knew a static image just wouldn't capture it so I spent some time making an animation of the radar images. Unfortunately, I had to do this by hand as there is no way to download the radar loops.

The time on this is from UTC 0048 to 0158. Every frame is 10 minutes and this covers 70 minutes of elapsed time. Local time in the twin cities this was from 7:45 to 8:45 p.m. Sunset was at 7:21 and twilight was at 7:50. It looks like the birds start taking off at twilight. Ignore the green storm on the east coast and the stuff moving in a band though Montana and North Dakota. The blue in the middle blooming and heading north is millions of birds migrating.


Minnesota Birdnerd said...

Kirk - You have to teach me how you did the radar loop. That is way cool!

Kirk said...

It was time consuming but worth it to capture this particular event. It was really impressive. Basically I did screen grabs of each frame of the loop as it appears online. There is probably a way to just have the server show you each image but I just snapped screen shots as it rotated through. It took a few tries to get all the images. I then used a program called GifBuilder to construct an animated gif file of all the images. It took a while.

The real kicker at the end was that Blogger does not let you use animated gifs in posts if you use the blogger editor to upload the image file. I posted up the animated gif but Blogger stripped out the animation. So, I uploaded it to google documents instead and then just linked to the image which worked great.