Weather & Songbird Migration

March 21, 2007

Dr. David Aborn

Dear Students:

Welcome to the first official day of spring! While the weather may not be able to make up its mind whether it is winter or spring, the birds know it is time to get moving! The cold front and storm system that brought so much snow and cold to the northern part of the US didn't force as many birds to land as I had anticipated, but as I mentioned last week, it is still too early for large fallouts. There were still some interesting events, however.

Radar Image of Flocks Migrating From Cuba to Florida!
One of the most interesting events occurred before the front reached the eastern US. Ahead of the system were southerly winds and no rain, which meant good flying weather for migrants. Even though warblers, vireos, and most other migrating songbirds are too small individually to be picked up by radar, flocks of migrants can be detected. This radar loop (below) shows birds migrating from Cuba to Florida in advance of the front!

Click image to enlarge

Migrating Flocks Show on Radar

Go here to see a recording of National Weather Service radar in Key West, Florida. The images show flocks of migrants flying from Cuba to Florida! The flight occurred during the night of March 14th. The next two days, March 15th and 16th, birders reported a wide variety of warblers and vireos throughout the state. These included Hooded Warblers, Black-and-White Warblers, Yellow-throated Warblers, Northern Parulas, White-eyed Vireos, and Red-eyed Vireos.

Migrants Moving In
Farther west, Texas had been experiencing several days of rain as a low pressure area sat over the state. When the system moved east and skies cleared, migrants moved in. The first Black-throated-green Warblers, Yellow-throated Warblers, Black-and-white Warblers, Prothonotary Warblers, and Louisiana Waterthrushes were seen.

Going even farther west, weather conditions were good for migration all week, and migrants trickled in from the tropics. Swallows were still the most common sight, but California also reported an Orchard Oriole, Rufus and Allen's Hummingbirds, a Plumbeous Vireo, a Tennessee Warbler, and a Summer Tanager. The first Rufus Hummingbirds and Allen's Hummingbirds made it into Oregon.

What Will the Weather Bring this Week?

• A cold front is moving across the eastern half of the country. It is a weak front, which means the winds behind it are not strong, and it does not have much rain with it. Thus, for most of the country, skies will be clear and winds will be light. This will allow birds in the southern US to fly northward and birds coming up from the tropics won't find any problems.
• Another front Is moving in off of the Pacific Ocean. This one has more rain with it, so there could be some small fallouts out West.
  

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