Flying in the Dark
After a week of warm days and south winds, the weather has abruptly changed in the Upper Midwest. With strong north winds and cooler temperatures today, tonight is shaping up to be one of the biggest nights for autumn bird migration. Fall migration is higher in numbers than spring due to all the new offspring that are now on their first migration.
As of 9:43 PM, an estimated 1.2 million birds have flown over my county so far this evening. As you can see from the graph below that number is way above the historic average.
The BirdCast website also shows in real time how the migration is progressing with its live bird migration maps. Tonight’s screenshot at 9:40 CDT shows there are approximately 1.169 billion birds in flight at that given moment!
BirdCast uses the NEXRAD weather surveillance system which is a form of Doppler radar to get its estimates of the bird populations. These large number of birds show up on Doppler radar just like storm events except the birds show up as circles of differing intensities over the Doppler locations. Here is the NEXRAD screen shot taken at the same time which shows how BirdCast mirrors the Doppler map.
Night-time bird migration is an incredible phenomenon that goes unnoticed due to the darkness. Imagine if this amount of birds migrated during the day instead of the night - we would be astonished by the sheer numbers. Night migration is beneficial for the birds as the air is cooler, less dense to fly through with the stars and moon used as navigational aids. The birds face real challenges now with our excessive use of lights at night especially buildings with large amounts of glass. Unfortunately two nights ago, the city of Chicago had a massive influx of migrating birds that created many fatalities due to collisions with buildings.
During this time of year, I wish meteorologists talked about this event to educate the public on what is actually happening at night and how important it is to turn off all unnecessary lights during this time. There are efforts to help. Audubon founded a Lights Out Program to help mitigate the danger of collisions due to disorientation from bright lights.
Every year, billions of birds migrate north in the spring and south in the fall, the majority of them flying at night, navigating with the night sky. However, as they pass over big cities on their way, they can become disoriented by bright artificial lights and skyglow, often causing them to collide with buildings or windows.Â
After flying all night, these nocturnal migrants need to feed so don’t be surprised to see a new species or two in your yard or at your bird feeder tomorrow.
I learned a lot about the migrating birds from this posting. It's amazing. Then read yesterday's paper about the incredible numbers of songbirds that flew into a building in Chicago killing almost 1000 of them during their night flight! Very timely post. Thanks Lili!