Weather and Songbird Migration: March 9, 2016
By Dr. David Aborn

Western tanager  

Western tanager

Barn swallow
Barn swallow


Dear Journey North,

Signs of spring are everywhere; tulips and daffodils are starting to sprout, days are getting longer, pollen is covering the cars, and most importantly . . . migrants are arriving!

Progress Northward
Last week I mentioned that as soon that cold front passed and the high pressure moved east by the weekend, winds would shift to the south and migrants would start arriving in the eastern U.S. Well, they are moving in!

New Gulf Coast/Southern/Western Arrivals
There are many Tree Swallows here in Tennessee, Purple Martins arrived in North Carolina, and the first Barn Swallow and Black-chinned hummingbird arrived in Texas. Out west, they have had good flying conditions for most of the week, so they have had more birds showing up. Lucy’s Warblers, Western Tanagers, Rufus Hummingbirds and Anna's Hummingbirds were seen in Arizona, while Summer Tanagers, Black-and-white Warblers, Western Kingbirds and Barn Swallows showed up in southern California.

Weather Map  


This Week's Outlook
So will birds keep arriving this week? Let's look at the weather map and see.

  • The western U.S. has been getting a lot of rain the past few days, so all those birds I mentioned have had to stay where they are. Things have cleared out, so now they can head north and new birds have good weather for their arrival.

  • The front that brought all that rain out west is now in the central US, and it is moving pretty slowly. The predictions are for up to a foot of rain in places like Louisiana and Mississippi over the next few days, which means birds won't be going anywhere for a while.

  • If migration were in full swing, that situation would create what’s known as a fallout. Many birds cross the Gulf of Mexico during migration. The crossing is a 1,500 mile, 18-hour non-stop flight. When these birds reach the Gulf Coast, they are already exhausted. If they encounter rain or headwinds, it makes flying even more difficult, so they quickly land in very large numbers -- hence the term "fallout." Birders always look for fallouts because they can see large numbers of a wide variety of species.

  • In the eastern U.S., skies are clear and winds are from the south, which makes for good flying, so birds that are here will be able to head farther north, and new birds will be able to arrive from the tropics. The cold front and rain will arrive in the east by the end of the week, and it is supposed to rain all weekend, so the birds will have to make themselves comfortable and wait it out.

Hopefully you are getting the hang of reading a weather map and what it means for migration. If not, don’t worry; there is a lot of migration yet to come, so you will get lots of practice! Take care.

Dr. David Aborn, ornithologist  

Take care,

David Aborn
North Chickamauga Creek Conservancy
Chattanooga, TN

Next Update: March 16, 2016