For migrant birds in North America, 2011 emerged with a startling truth?things that go "boom" in the night can kill you. On New Year's Eve in Beebe, Arkansas, more than 3,000 red-winged blackbirds and migrating birds of several other species tumbled from a night sky lit with fireworks. Preliminary necropsy reports from the U.S. Geological Survey's National Wildlife Health Center (NWHC) in Madison, Wisconsin, have confirmed "impact trauma" as the culprit in the bizarre event, reports the Wildlife Management Institute.

According to press releases posted by the Arkansas Game and Fish Commission, unusually loud explosions from the firework display caused nearby birds to flush from their roosts. Forced to fly low in order to avoid the effects of the ongoing light display, birds slammed into houses, towers, trees, vehicles and other obstacles, most of them likely dying on impact. Thus far, sampled birds have tested negative for disease, parasites and toxins.

In a seemingly apocalyptic second act, a mixed bag of more than 500 birds (including red-winged blackbirds) was found dead and dying near a power line outside of New Roads, Louisiana just three days later. The diagnosis? Impact trauma.

"On the birds we examined, we consistently found shattered beaks, broken backs, broken wings, trauma to organs and internal hemorrhaging," said Dr. James LaCour, State Wildlife Veterinarian for the Louisiana Department of Wildlife and Fisheries. LaCour and his colleagues believe a fast-moving cold weather front plus traffic on a railway line flushed roosting birds directly into a nearby power line. "Nearly all of these birds were found within 10 feet of either side of the wires," noted LaCour. "This incident was pretty cut and dried."

However, recent media coverage of several large-scale wildlife die-offs has created a national stir, inciting popular theories ranging from biblical prediction to extraterrestrial intervention. Scientists have been quick to note that attempting to draw correlations or large-scale conclusions regarding these coincidental events is foolhardy and indefensible.

Research from the NWHC indicates that these die-offs, while startling in their scale, are neither unexpected nor particularly uncommon. "Although wildlife die-offs always pose a concern, they are not all that unusual," said Jonathan Sleeman, Director of NWHC.

Since 2000, NWHC has documented 188 bird die-offs in the United States involving 1,000 or more individuals. At least three of those events involved no fewer than 10,000 birds, rendering the Arkansas and Louisiana incidents puny by comparison. Put in the context of mortality events in all animals, the numbers become even more staggering. In the last eight months alone, NWHC has recorded 95 fish and wildlife die-offs in North America. Placed within a longer time scale, data show that these events occur nearly every other day.

While these occurrences evoke curiosity, surprise and morbid fascination, they draw into focus the unfortunate effect that human-dominated landscapes can have on North America's wildlife resources. Alteration of habitat due to urban sprawl, roads, power lines and energy development take particularly heavy tolls on migratory bird populations? According to the U.S. Fish and Wildlife Service, between 4 million and 5 million migratory birds die annually from collisions with signal towers alone. Bird collisions due to confusion by man-made light sources have racked up spectacular death tolls that dwarf Arkansas' New Year's Eve incident. In 1957, for example, more than 50,000 birds of 53 species were killed in one night when the light beams from a ceilometer in Georgia caused the birds to collide with nearby buildings. And there is concern about the impact (single event or cumulative) of wind turbines on migrating birds.??

Although alarming, large-scale die-offs of fish and wildlife are not unusual and mostly unavoidable. Nevertheless, avian biologists observe that improved siting of artificial structures within the migration lanes of neotropical birds will help reduce die-off events. Furthermore, they note, the gravest threat to wildlife resources is not individual mortality events. Rather, the displacement and decline of many species of birds and other wildlife are the result of ongoing habitat alteration and fragmentation caused by development and other human activity. (mcd)