Protecting a Threatened Raptor

As birds of prey, Swainson's hawks appear formidable. They can soar effortlessly for hours. With sharp talons and keen eyesight, they hunt small rodents, lizards, and frogs with deadly accuracy. And they hold the record for the longest migration of any North American hawk, about 10,000 miles (round-trip).

But their population--numbering about 450,000 in the U.S.--has declined greatly during the last 50 years. This is particularly true in California, where the Swainson is listed as threatened.

Last spring (and for the next five years) DWR environmental specialists trapped, measured and tagged hawks as part of an effort to monitor and protect hawks nesting during the construction of the Grant Line Canal barrier in the Delta and, as mitigation, place satellite transmitters (starting this spring) on the hawks to track their migration route. The transmitters, about the size of small pack of gum, weigh one ounce and are fitted to the hawk like a backpack. They can relay back about 70 locations for each hawk over a nine-month period.

Learning where they migrate will help save the species. Swainson's hawks winter in South America, where they can be exposed to pesticides banned in the U.S. Since they often travel in large flocks and feed together, such exposure could wipe out a large percentage of the approximately 800 breeding pairs that reside in the Central Valley. By knowing their destination, a program can be developed to persuade area farmers to change their practices to help protect the hawks.