A migratory bird “fallout” event is almost always a source of mixed emotions for birdwatchers and enthusiasts. On the one hand, fallouts give birders the opportunity to see sometimes thousands of migrating birds from hundreds of species; birds that would normally fly overhead by night without leaving a trace. Obviously, for birders coveting that elusive “life lister” sighting, this is a hugely exciting prospect. On the other hand, fallout events mean that something has gone wrong on the migration route. This can have serious consequences.
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A migratory bird “fallout” occurs when, during the migration season, inclement weather or some other interference occurs that prevents migrating birds from continuing their journey on schedule. They descend from the sky en masse to rest and refuel in a location that they would normally pass through quickly. Local birders are stunned when they awaken to see thousands of unusual visitors hanging around backyards and parks. But fallouts mean delays that can ripple through the population and ecosystem. Most birders enjoy fallouts, which are admittedly quite rare events, with the knowledge in mind that the best outcome for their unexpected visitors is a short rest and a quick return to their original migration route.
This is what birders in Chicago experienced this Thursday morning when the city awoke to an enormous fallout of migrating birds. The birds, many of which were warblers, swarmed the Chicago area, filling trees and delighting birders who shared their observations on social media throughout the morning. At one point, monitors suggested that as many as 100,000 birds were passing through the area each hour.
The intensity of this migration event is matched only by the intensity of the tragedy that followed. Windows and light pollution are a constant threat to migrating birds. Birds are unable to see glass and may slam into reflective glass in the daylight. Overnight, lit windows disorient birds, many of whom navigate by moonlight. Many conservation agencies have been urging citizens, but especially building owners for large glass buildings, to “bird-proof” their windows and turn off non-essential lights after dark.
For nearly 1,000 birds, these changes did not come soon enough. Just as birders were enjoying this unprecedented fallout, a single building in Chicago was the cause of death for more than 960 migrating birds. McCormick Place Lakeside Center was littered with dead Palm Warblers, Magnolia Warblers, Tennessee Warblers, and Myrtle Warblers amongst other migrants. This is more than 20 times the previous record for bird fatalities caused by a single building in a single day.
Rainy conditions pushed the birds to fly low toward the McCormick Place building, whose windows were lit. Despite repeated calls from conservation groups, the building was not “bird-proofed” in any way. While this tragedy is shocking and the death count is staggering, conservationists and conservation-minded birders are not surprised. Each year an estimated 100 million to 1 billion birds die by striking windows. Tragic events like this one underscore the desperate need for change to prevent further loss of avian life.
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