Today to ponder.
It is nearing the end of April, and today I had an FOY experience. That’s extreme birder’s coded lingo for “first of the year” sighting or identification of a bird. That is, for the first time this year, I heard the distinctive flute-like call of the wood thrush, Hylocichla mustelina, singing in the woods near our home. The call lets me know that at least one of “our” birds has returned safely from its “winter vacation” in Central America or southern Mexico.
Advances in our knowledge of bird migration made a big jump in the past few years with the development of miniaturized recording devices that we can attach to leg bands of large birds or that can be strapped on the backs of smaller songbirds. Depending on the model, such recorders (called geolocators) weigh only a gram or two and record time, temperature, wet/dry conditions, and sunrise and sunset times. The smallest models register only sunrise and sunset times, but with that data it is possible to calculate position within 100 miles.
Canadian ecologist Bridget Stutchbury strapped the tiny data loggers onto 20 purple martins and 14 wood thrushes in northern Pennsylvania during the summer of 2007.The next summer the tiny geolocators were retrieved from five wood thrushes and two purple martins. When the data was downloaded and analyzed, Stutchbury and her associates were astonished to learn that the purple martins reached the Yucatan Peninsula in just five days, a 1,500-mile trip. After a three-or four-week stopover, they continued on to Central and south America. The wood thrushes took their time going south, spending one or two weeks in the southern United States before crossing the Gulf of Mexico, and a couple paused for a few weeks on the Yucatan also before going on to their wintering grounds in Honduras and Nicaragua. But the return trips in the spring were two to six times more rapid. One purple martin female flew nearly 5,000 miles from the Amazon basin to northern Pennsylvania in 13 days with four of them being stopover days. Wood thrush data showed a similar hustle on the spring return, with all but one of the thrushes Gulf.