March 20

Migration is one of the most riveting of bird behaviors, marking the seasons and varying our bird lists over the course of a year. Migration may also be the saving grace of some species as climate change alters the world. Some migrations are epic and long distance. We’ve talked about the migration of the Aleutian Canada Goose in an earlier post. They move from the Arctic to at least California’s Central Valley, with a dramatic stop-over in Crescent City. Other birds move short distances, from the mountains in summer to warmer valleys in winter. Regardless, migrating birds must store up fat before departing, and apparently beef up their muscle tone as well. That is doubtless what those Sandhill Cranes were doing in agricultural fields in the Delta. Birds have an annual clock that prompts readiness to migrate as well as the ability to be flexible when it rains or is windy in the wrong direction. Birds have genetic encoding that directs their flight, especially for younger fliers. In addition, they also use magnetic north sensors and the sun and stars to guide their flight. They also sense the land, or sea, and avoid barriers. We’ve had Dark-eyed Juncos at our bird feeders in the mountains last month and this. They are seed-eaters. They are variable migraters, travelling from none to 2500 miles, according to the literature, so it is difficult to know where our travelers have been. They come every year, however. The females apparently migrate further than the males (up to 300 miles further in some studies), so perhaps ours are a girls’ club travelling to the summer breeding spot. Finally, Juncos are a little snow-tolerant, so we are trying to believe that their arrival heralds spring, even though it is still snowing in our foothills. Total to 3-20: 60