Wednesday, January 14, 2009

Bird Movements - How Little We Know

Over the last few months I've come across some amazing tracking studies that are resulting in huge revelations about bird migrations.

At Joe Gaydo's lecture this summer he talked about a surf scoter that had been tagged in Puget Sound was subsequently tracked to Saskatchewan, Nunavut, and Alaska. It raises the question of what we're really witnessing when we see a local bird decline, like of surf scoters here in the San Juan Islands. Are there really fewer surf scoters, or are they just spending time in a different part of their habitat? Are they really declining, changing their patterns due to some detrimental local factor, or following some longer-term shifts in habitat usage that function on a scale longer than we've been monitoring their population numbers?

The USGS Alaska Science Center studies the migration patterns of bar-tailed godwits. These are maps you absolutely have to see, showing the migration of godwits from Alaska to western Australia and New Zealand. Scroll down the page to see the amazing trip of godwit E7, who from mid-March to early September travels 18,000 miles as she practically circumnavigates the Pacific Ocean. In this article that details her flight, you'll be amazed to learn that many legs are made with nonstop travel - up to 8 days and 7200 miles at a time! Godwits live to be more than 20 years old, so may fly an astonishing 288,000 miles in their lifetime.

Another amazing shorebird flight took place when a whimbrel was tagged in Virginia in May. They thought she would head to breeding grounds in Hudson Bay, but instead flew straight on to Alaska. She flew 3200 miles in 146 hours - nonstop. You can learn about her and her trip to Alaska in this Nature Conservancy article. Unfortunately, on her migration back to her summer grounds, after stopping over in Washington, she met her demise on a sandbar in Minnesota. This is an important fact in itself, since it is unknown how many birds die during migration.

The most recent tracking study that came to my attention was of Elizabetha, a peregrine falcon. According to the Falcon Research Group 2009 winter bulletin, she was tagged in Chile and made her way to Canada to breed. Once she started her southbound migration, she set a world record by flying 954 miles - from New Jersey to Florida - in a single day.

There are many pros and cons to tagging and tracking animals - whether they be whales, birds, or fish, and discussion of tagging all three is happening locally. Still, the discoveries made by such studies are astounding, and in many cases are revolutionizing our understanding of the organisms, as is pointed out in the FRG bulletin linked above.

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