How to observe migration at night
Most people don’t realize that birds migrate at night starting at sunset. Numerous studies show that songbirds use their constellations to navigate their movement to their desired location. On cloudy nights they can use the small opening of the sky or correct themselves once the sky opens again. The amount of daylight is what triggers these birds to start moving and today there are many new methods that Ornithologist are using to study their migration. Currently, Powdermill Nature Reserve is conducting a bioacoustic study where they are collecting nocturnal flight calls made by these birds, which allow them to survey which species are moving through the area. For more info, check out the Powdermill page at: http://www.powdermill.org/research/bioacoustic.htm
I am an amateur weather observer and been “trying” to use NEXRAD radar to assist me in banding these little owls. As you’re aware, NEXRAD radar is an important tool for meteorologist in following rain and snow storms that are in the area. If you listen quietly while checking the nets for owls, you can hear the call of these birds moving overhead. Then you know to check the radar to see what is truly going on. Now because the NEXRAD radar is so sensitive, it can pick up the movement of insects, bats and even dust that is in the air. Typically meteorologist call those spots observed on the radar “ground clutter”. In the fall and spring we call those spots “bird migration”. I choose to use the Weather Underground website located at http://www.wunderground.com and I decided to pay the membership to receive the longer images. If you use the NEXRAD Storm Velocity feature, you will observed the “ground clutter” (after sunset) moving North in the spring and the movement South in the fall. For most nights that I blog, I will be uploading images on the bottom of the radar collected from Weather Underground and if you click on the image – it will show the image moving!
This first clip is from last night’s radar showing the movement of the birds from 8pm EDT to just after midnight EDT! Yes, you’re looking at thousands and thousands of birds moving through Western New York But, it is really hard to distinguish what direction its moving and if it could possibly be fog in the area. For that you use the map below looking at the Storm Velocity.
This is the same image but is showing the birds movement. Green means it’s moving towards the radar (which is located in the center of the screen) and red means it’s moving away from the radar. If you click on the link, you will notice that the movements of the birds are coming from the NW direction (moving towards the SE) and then as the evening progresses the birds start changing their direction heading due south. Now if you think that’s cool, check this next map!
Here you see the front map of the North Eastern United States starting just before sunset. Right at 7:30 the birds will start to appear at each of the NEXRAD radar stations and you can then get a larger perspective of how many billions of birds (aka: Ground Clutter) are moving at one time. You probably can see why everyone finds this so interesting to learn about. For more info on Radar Ornithology, please visit the Clemson University website (where I learned everything I know about this subject). Below is the image from tonights radar where there isn’t much movement (you can see a little) but you are able to see some of the rain storm entering the screen in the upper left!
Obviously, I didn’t catch any owls tonight with strong 10-15mph Southern winds and clear sky.