Bird Migration – November 6, 2019
Given a lot of recent avian activity by Canadian geese here in Colorado as the temperatures drop and the snow arrives, today’s topic is on bird migration.
The timing of bird migrations is an intriguing phenomenon in nature and scientists are *still* working to solve its mysteries! According to Ian Newton, author of “The Migration Ecology of Birds,” many long-distance migrants are remarkably regular in their departure and arrival dates. That’s a crucial part of their continued survival, as it ensures that birds arrive in nesting areas just as environmental conditions become suitable for breeding, and then leave before they change. But birds seem to adjust to variations in weather that occur from year to year, which suggests that their migratory instincts are triggered by external stimuli.
While we know what conditions attract them (warm temperatures, food availability), scientists are still trying to figure out the mechanism that actually tells birds it’s time to take off. All About Birds, a site maintained by Cornell University’s Lab of Ornithology, offers a hypothesis that birds have some sort of “undiscovered interface” – basically, a sort of biological wifi connection – that enables them to sense distant temperature and weather conditions.
The secrets of birds’ navigational skills aren’t fully understood either, partly because birds combine several different types of senses when they navigate: they can get directional information from the sun, stars and by sensing the earth’s magnetic field. Information also comes to them from the position of the setting sun and landmarks seen during the day. Recent studies using eBird data are revealing that many small birds take different routes in spring and fall, to take advantage of seasonal patterns in weather – riding the prevailing winds saves calories!
photo: Ricardo Peña
For more reading: