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Nocturnal Migration Part 2

posted by Tim Avery at
on Friday, April 15, 2011 

Earlier this week I posted a very basic intro to nocturnal migration. Very basic. I have some more in depth information to post (part 3 and on) but before I get into that I want to take a minute to show a few images and talk about the last couple nights. Migration is in full swing in Utah. The reports coming in from the day time can attest to that--with the arrival of a handful of different shorebirds, swallows, swifts, hawks, waterfowl, terns, gulls, and grebes. It's not even close to the height of the season yet, but things are getting exciting.

First, lets take a look at what migration has looked like the past 4 nights (04/12-04/15):


Monday, A storm approaches migrants. Tuesday, migration!


Wednesday, A storm covers the north. Thursday, silent night.

On Monday and Tuesday migrants were moving across the north. A storm system passed through Monday night, and stalled migration by about 4am (I have an animation below to show). On Tuesday it was clear skies and great conditions as birds moved north. Wednesday was stormy all night and nothing really happened with migrants. Thursday night was clear, but the storms from the previous 24 hours seemed to keep everything grounded as the skies were clear all night. can you see the difference between those nights based off my comments along with the radar images?

That is how migration goes. Some nights are amazing and others are lackluster. The weather plays a role and sometimes none of it seems to make sense. Hopefully I will be able to use a few storms in the coming weeks to highlight effects on migration and how to use the radar information to influence birding. That being said take a look at the image below. It's an animated image of the night of the 11th into the 12th starting at sunset at 8pm and going until 4am. The start point is the slide with the line that spikes on the left side shooting off the edge of the radar. That is the sun reflecting off the radar at sunset:

migration on radar

After the first slide you can see a bunch of migrants appear on the center of the map over the Wasatch. As the slides progress the migrants become more dense, and the storm over the West Desert movers towards the Great Salt Lake. By the last slide the storm is over the lake and the migrants are all but gone from the radar (except for those east of the storm over the mountains). That is at about 4am.

Speaking of storms, over on the National Weather Service Site tonight there is a great image of what severe thunderstorms look like approaching the eastern seaboard:


All those reds, yellows, and greens are very reflective and this is a common sight as storms pass across the continent. To the south you can see the light and medium blues radiating from the doppler stations as migration is happening where the storm hasn't hit yet.

Okay, so I have shown you a bunch of radars and explained what is happening on them--what next? I think for this post we are about tapped out. In the next post I will explain what the reflectivity colors mean, as well as talk about velocity radar screens, which look like the image below:


That's right, not only can we tell how dense migration is, but we know how fast the storms are moving, and how fast the birds are moving too. From there I will talk about how the radar works, and a little more of the science behind what we are seeing. But that's next. So get out and enjoy migration, and if you really want to geek out, check out the radar to see what's happening at night!

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2 Comments:
Blogger Susan said...

Thanks so much for taking the time to post this, it is so interesting to me. I am definitely going to be looking tonight!

April 15, 2011 at 10:34 PM  
Blogger Tim Avery said...

@Susan: No problem. This is fun (extremely nerdy) stuff when it comes to birds. The science behind how they get here is something that is so strange, and the ability to track, and watch it to a certain extent is certainly worthwhile for some of us.

The best stuff is yet to come--that's talking about listening for night migrants; the real life birding portion of nocturnal migration.

April 16, 2011 at 5:08 PM  

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