Outdoor Ontario

Birding Reports => Migration Movements => Topic started by: Andreas Jonsson on April 30, 2010, 01:06:56 PM

Title: Radar observations of bird migration
Post by: Andreas Jonsson on April 30, 2010, 01:06:56 PM

There was heavy bird migration across the lake last night visible on the Buffalo radar. Should be good out here today! Unfortunately I have to work...

Title: work??
Post by: Howieh on April 30, 2010, 02:24:37 PM

Of course you realize you're not setting a very good example for the newbies by letting work interfere with your birding!

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Post by: Andreas Jonsson on April 30, 2010, 03:09:49 PM

Haha! Well, I'll be catching up in the weekend.

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Post by: Niloc on April 30, 2010, 06:38:15 PM

I think you're are right on I went to Ahbridges Bay today and the trees on the waterfront were swarming with White Throated Sparrows...

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Post by: Andreas Jonsson on April 30, 2010, 11:14:38 PM

The radar (http://www.rap.ucar.edu/weather/radar/displayRad.php?icao=KBUF&prod=bref1&bkgr=black&endDate=20100501&endTime=3&duration=4) is looking very good for tomorrow as well. Haven't seen such large values all spring! See you out there!

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Post by: Andreas Jonsson on May 11, 2010, 01:45:15 PM

Last night the migration was more intense that usual, according to the Buffalo radar (http://www.rap.ucar.edu/weather/radar/displayRad.php?icao=KBUF&prod=bref1&bkgr=black&endDate=20100511&endTime=11&duration=12). Should be good out there today.

Title: How to use NEXRAD?
Post by: strimackus on May 11, 2010, 02:16:46 PM

I've heard NEXRAD mentioned a bunch of times, but am not totally clear on how to use it. As I understand it, it's purpose is to track precipitation, but it can also be used to track migrating birds. How are you able to distinguish between migration and precipitation? Also, the colours appear to more or less radially symetric around the center of the image. Wouldn't migration lead to higher values north of Buffalo, over the lake?

Thanks.

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Post by: Andreas Jonsson on May 11, 2010, 03:04:52 PM

Yes, weather radar systems are designed to detect the intensity and location of precipitation. Also, since NEXTRAD is based on Doppler radar the velocity of the precipitation (generally moving with the horizontal wind) can also be detected. So with regards to bird migration one can observe both the intensity of the migration, and in which direction it is heading.

Just briefly, in the absence of precipitation these radars use a very sensitive mode that easily detects birds and also insect swarms and bats! It's pretty cool. Song birds migrate preferentially at night, and you can see on the radar images that the birds take off just after sunset leading to an increased signal until about midnight after which the signal decreases again as birds descend. There is an excellent tutorial on radar ornithology here (http://virtual.clemson.edu/groups/birdrad/COMMENT.HTM), which I really recommend reading, particularly to better understand the geometry of the measurements.

Unfortunately the Canadian radars are not as useful, as all signal that is not interpreted as precipitation is generally filtered out.

For southern Ontario and Point Pelee, I recommend using the Cleveland radar, here (http://www.rap.ucar.edu/weather/radar/displayRad.php?icao=KCLE&prod=bref1&bkgr=black&endDate=20100511&endTime=11&duration=12). They appeared to have some pretty intense migration down there too last night. In fact those images serve as a good example to illustrate the different appearance of birds and precipitation. The round blob that appears centred around the radar station is birds and the layered feature slowly approaching from the south-west is rain.

You can see radar imagery for any NEXTRAD station here (http://www.rap.ucar.edu/weather/radar/).

Note that the radar links included in this post will only work for a limited time, as the radar data is only available online for a couple of days.

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Post by: Pat Hodgson on May 11, 2010, 03:19:39 PM

Two other things to point our with Nexrad, it has two modes, precip mode and clear air mode.  You don't get to select this, it depends on the weather in the area.  This is indicated in the upper left in the images linked above.  In precip mode, there is usually rain around and it is less sensitive, so you are unlikely to see birds.  In clear air mode, it is more sensitive but also seems to often have a lot of clutter near the centre of the image - after a while you learn to disregard it.  Also note that on the site linked above you can set the loop duration to more than a single image - do so.  In the right conditions you can see birds take off after sunset all along the contours of the lakes.  On the Buffalo radar, you can see a radar image that matches the southern shore of Lakes Erie and Ontario, and Long Point, take off and move north.  Incredible!

Title: radar
Post by: tellin on May 11, 2010, 05:17:05 PM

Hello,

I've read the following posts about radar but am still unclear about how to interpret what I'm seeing. I Googled NEXRAD and Buffalo and see various colours of (precipitation?) over the lake. There is a colour key but it doesn't specify if it's precipitation.

I don't see where precip mode and clear air mode are indicated, or where you set the loop duration. Also, a tutorial on radar ornithology is mentioned in one of the previous posts. Would you mind posting it again?

Thank you.

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Post by: Andreas Jonsson on May 11, 2010, 06:17:25 PM

Hi tellin,

you cannot look any radar image, there are different data products. You want to look at "Reflectivity" data, I suggest you go here (http://www.rap.ucar.edu/weather/radar/).

There is a bit of learning curve to understand how to interpret the radar images. Birds appear as "soft" round clouds centred around the radar station. Clouds and precipitation can occur anywhere in the image, and generally have significant stricture and heterogeneity.

Have a look the FAQ and video here (http://www.woodcreeper.com/radar-migration-faq/), I'm sure it will get you going. If not, ask again.

The tutorial on Radar Ornithology can be accessed by clicking the link in my previous post.

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Post by: bidonnant on May 12, 2010, 12:27:48 AM

This site has a video tutorial about halfway down the page which I found very helpful:
http://www.woodcreeper.com/radar-migration-faq/

Cheers,
JF

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Post by: strimackus on May 13, 2010, 06:17:09 AM

Thanks for the tips and resources. Now I understand how these NEXRAD images work. Pretty cool.

According to the radar (http://www.rap.ucar.edu/weather/radar/displayRad.php?icao=KBUF&prod=bref1&bkgr=black&endDate=20100513&endTime=11&duration=12), looks like there was another migration across the lake last night.

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Post by: Andreas Jonsson on May 13, 2010, 10:26:26 AM

Yes, it looks pretty good for today.

But note that the radar is so sensitive that it will show some migration every night. You have to look at it over time, and compare the intensity to the other nights. Deep blue colour is generally as intense as it goes. Nights with weak migration generally show up with brown colours.

I've noted however, that the migration is less intense in our region than further west (central flyway) and at the east coast

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Post by: Andreas Jonsson on May 14, 2010, 01:56:15 AM

Having just said that, I note that the migration just exploded into the greens tonight after the rain passed. Will be interesting to see what's out there tomorrow.

Title: migration
Post by: tellin on May 15, 2010, 10:26:38 PM

If I am reading the radar correctly, tonight the dominant colour is yellow, and seems to be travelling at 15-20 knots per hour over L. Ontario. Is this a moderate movement of birds?

What are the features that indicate a movement of birds? I watched the video tutorial but am still not clear on how this works.