Week of September 4, 2022 – September 10, 2022
by Anna Stunkel, Environmental Educator
While many of us may know songbirds as generally diurnal creatures, a mass migration of them occurs at night during the spring and fall. Nocturnal migrants include birds such as warblers, thrushes, vireos, and sparrows. These little birds may fly by night in order to avoid the watchful eyes of hawks and other predators, to save energy by flying when it’s cool, and to navigate using the stars. This mysterious world of nighttime migration is hidden from most of us, although you may notice birds’ chirping flight calls high overhead when darkness falls. On especially busy nights, birds can even be seen occasionally flying in front of a full moon.
Before migrating, birds increase their fat stores so they can survive the long journey ahead. Ruby-throated Hummingbirds will even double their weight (or more) before their long southbound trek, which includes a diurnal and nocturnal journey across the Gulf of Mexico. Migrating birds must watch out for predators and human-made obstacles such as buildings and cell towers. They are also attracted to and disoriented by lights, which increases the risk of building and tower collisions. You can help these migrating birds by turning off non-essential lights from 11 pm to 6 am during the migration season.
Birds are very sensitive to changes in their environment that can help them to forecast the weather, in turn affecting when and how they migrate. They can feel changes in barometric pressure, and will consume more food when pressure decreases. Evidence even suggests that Veeries (a species of thrush) can forecast the severity of a hurricane season months in advance. In years with severe hurricanes, Veeries appear to time their nesting and migration accordingly so that they can wait out big storms before crossing water. This is cause for concern, since climate change could cause Veeries to increasingly cut their nesting seasons short.
Migrating birds are visible on weather surveillance radar, which has led to some interesting opportunities for research. If you’re interested in learning more about how to forecast and keep up with nocturnal bird migration, the Cornell Lab of Ornithology’s BirdCast program is a helpful resource. Using radar, the BirdCast website shows maps predicting the intensity of bird migration in different regions of the US. You can check out the website here: https://birdcast.info/