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Nocturnal Migration Part 1

posted by Tim Avery at
on Friday, April 8, 2011 

Thank goodness Jerry Liguori has been busy posting and sharing some great information the past couple weeks. I have gotten behind on blogging and let a couple ideas for posts slip by. Trying to get back into the swing of things just as spring migration set in on Utah let talk about migration—nocturnal migration that is!

So a quick crash course in songbird, shorebird, waterfowl, owl, and so on and so forth migration—basically anything but diurnal raptors. All of the above mentioned migrate primarily at night. There is definite day time migration, but the vast majority of long distance migration happens why most of us are sleeping. Yes that’s right most birds migrate at night. Seems weird, is weird, but it’s the way of the wild.

Second point regarding nocturnal migration. Did you know that you can “watch” migration pan out on weather radar? Say what?!?!? Yes, you can see the density of reflective objects on NEXRAD radar and make out the differences between wet weather, birds, insects, dust, bats, and other objects that are picked up on the radar. Below is the radar from tonight.

Unfortunately, this is showing weather and not birds. Much of the last week has been similar and on clear nights there hasn’t been much showing up on the radar.

Weather shows up as splotches usually with some type of direction (typically heading east), but often stretched out as storm bands move through the radar area. Typically these storms show up as very dense on the radar mostly green with dark blue edges. Yellow and red are usually at the center of the most intense storms showing the most reflectivity. Birds don’t show up on radar like this. Usually when migration is in full swing you can see a donut shaped ring around the center of the radar image (often without a hole in the middle). The donut is typical a light blue with some dark blue and green where birds become more dense. But instead of showing up as globs of color the birds actually show up as dots giving a speckled appearance to the radar. In comparison to the image above over Utah tonight, take a look at the gulf coast right now at the same time.

See the difference? Quite different in appearance, and helpful in reading radar images at night to try and read migration. Right now millions of migrants are moving onto and and up the gulf coast as spring arrivals come from Central and South America.

That is where I am going to leave off tonight. Below are links to two sites I use to try and look at nocturnal migration. Over the next couple weeks hop on anytime between 10pm and 6am and you should be able to start reading the radar images. Part two of this series will be on the way in the next couple days as I delve more into reading the radar, and talk about how and why this information is important to birding.

NCAR NEXRAD Radar (click MTX to see northern Utah)

NWS Radar Mosaic (shows the entire U.S. on one screen)

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Blogger Vic Berardi said...

Excellent post Tim! I've been wanting to learn how to use these sites. Your explanation is concise and straightforward. Thanks!

April 9, 2011 at 7:20 AM  
Blogger Susan said...

This is the kind of post i love. I am learning so much. Thanks!

April 10, 2011 at 9:04 AM  
Blogger Tim Avery said...

@Vic Thank you. More to come in the next few weeks as migration heats up.

@Susan I'm glad you're enjoying the posts! This is why we created the blog (Jeff, Carl, Jerry, and Ryan), to share information about birds and birding and be able to openly discuss a variety of topics in a place where everyone can have a voice!

April 10, 2011 at 10:09 AM  

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