And they’re off! The annual miracle of songbird migration is officially underway, as millions of recent fledglings are setting off on their first southbound journey. Here in the Baltimore area, we  had our first major wave of migrants come through on Monday evening, Sept. 2nd. BirdCast estimates that nearly four million birds passed through our county that night, thanks to a cold front that dropped temperatures into the upper-50’s and a wind that shifted from the NNW—ideal conditions for southward flight. Over the next month or two, you can witness the wonder of migration by going for walks during mornings of similar weather. Ideally, you’ll want to find sunny patches at the edge of the woods to observe a bit of the feeding frenzy of weary travelers eager to refuel after a long night of flying. Be sure to have the sun at your back, so you get the best views; most songbirds have recently gone through their late-summer molt and are now wearing more dull plumage. This makes them tougher to pick out from the backdrop of greenery and the dull yellows and reds of early fall leaves.

Unlike spring migration, which is fast and furious, with most northbound birds passing through in just a few chaotic weeks in May, fall migration is prolonged and drawn out. It also follows a predictable sequence: shorebirds and swallows in August; flycatchers, warblers, and vireos in September; thrushes, then sparrows, in October; and, finally, most waterfowl arrive from the north in November. While September brings the greatest diversity of migrants, don’t expect to see many new species at your backyard feeders this month. The reason most of these birds are leaving our area is that they are strictly insectivorous and can’t subsist on seeds. You can look forward, however, to the arrival of several primarily Canadian species that join our winter bird community later in the fall—namely, Dark-eyed Juncos, White-throated Sparrows, and possibly some of the “irruptive” species (Red-breasted Nuthatch, Purple Finch, Pine Siskin) which head south in large numbers every few years, depending on the state of the northern conifer crops.

Migration is indeed a very dangerous—and exhausting—undertaking for birds. Roughly 40% of them (perhaps more) will not survive to return next spring. However, it’s a necessary risk for species that cannot find enough food here in the winter. Globally, human-related habitat loss is the leading cause of avian declines; habitat destruction for development is just as big a problem (or bigger) in many species’ Central or South American wintering grounds as it is where they breed here in the United States. Enroute between these two seasonal “homes,” however, avian migrants also encounter extreme (and worsening) weather events, wildfires, toxic chemicals in the environment, dwindling food resources, power lines, wind turbines, communication towers, and natural predators, not to mention the growing menace of outdoor cats. All of these potential—and largely anthropogenic—dangers take a toll on avian populations.

Predator avoidance, along with the energy savings associated with long-distance flight in cooler temperatures and less turbulent air, is, in fact, one of the main reasons most birds migrate at night. Sadly, we humans are making this aspect of their journeys more hazardous, too, through the proliferation of light pollution in our modern world. Birds use both the Earth’s magnetic field and the stars in the night sky to navigate. During overcast or foggy nights, however, birds lose sight of star formations and become easily fooled into heading toward distant urban or suburban lights instead. As they become disoriented in these artificially lit environments, many birds end up colliding with the glass windows of contemporary buildings. Even single-story ranch houses can pose a bird-glass collision hazard, particularly when the sun is low on the horizon. As tired migrants settle down at dawn or as they embark on the next leg of their journeys at dusk, these low-light situations make it easy for birds to mistake reflections of foliage for actual trees and shrubs. Indeed, colliding with glass on businesses, homes, and cars is now the third leading cause of bird mortality; as much as 10% of our avifauna is lost this way each year. 

-Brian Rollfinke, Director of Education and Outreach