For the Birds Radio Program: Tower Kills
On May 24, a major bird kill happened at a lighted tower at the Carlos Avery Wildlife Management Area.
On the night of May 24, migrating songbirds were pressing north through Minnesota. Most songbirds migrate by night, using stars to find their way. They don’t have good night vision—probably comparable to ours, or even a bit worse. But stars stand out in bold relief in the night sky, and as long as parts of the sky are in view, the star chart they memorized as tiny nestlings shows the way. Because they have such poor night vision, they migrate at high enough altitudes to be well above natural hazards such as trees, even atop hills and mountains.
Unfortunately, May 24 was a foggy night, blocking any view of the stars. Without their celestial navigation system, the migrants were confused and disoriented. As they flew above the Carlos Avery Wildlife Management Area, suddenly large numbers of them caught sight of a red light blinking in their airspace, as if to show them the way, and they drew closer and closer. But once they got into the lighted halo around the light, they didn’t know where to turn, so they milled around. Some collided with each other. Others crashed into guy wires or the tower itself. In the morning, there were hundreds, perhaps thousands, of dead and dying birds beneath the tower. Birds weighing a quarter or a third of an ounce are hard for us humans to find in tall grasses, but rats, ground squirrels, crows, gulls, foxes, coyotes, and feral cats, alerted by any crippled birds fluttering or peeping below the towers, find a smorgasbord of tasty treats and make quick work of the dead and wounded. If people arrive on the scene after sunrise, there is often little or no evidence of the carnage. So most tower kills such as this go completely undetected. But this time someone noticed dead birds at the Wildlife Management Area and alerted the Minnesota DNR D.N.R. workers collected 385 birds on the morning of May 25, and the next morning found another 34.
The list of the dead birds at this kill is pretty much a random assortment of late-spring migrants. Birds found in the biggest numbers were Tennessee and Yellow Warblers, Red-eyed Vireos, Swainson’s Thrushes, Common Yellowthroats, and American Redstarts, but the total included 15 species of warblers and five vireos, and Scarlet Tanagers and a Baltimore Oriole.
Of course, most nights, individual towers don’t kill a single bird, and some kill birds only once in a decade or more. Only when foggy weather coincides with a major migration movement do towers kill more than a handful of birds at a time, and except for a few towers in the US that are closely monitored, even large kills usually go undetected. Radio and TV stations, cell phone companies, and communications tower construction companies do their best to keep the public in the dark about the birds killed at towers. But tower kills can be far more devastating than the one in Anoka County. A single TV tower in Eau Claire, Wisconsin, killed 20,000 birds on a foggy September night in 1957, and the same tower took out 35,000 birds on a foggy weekend in September, 1963. The US Fish and Wildlife Service estimates that millions of birds are killed every year at communications towers. The problem has been recognized for at least 60 years. But birds are hardly effective lobbyists and can’t vote, so there has been little research done about the situation, especially in recent decades. It’s quite possible that different color lights, or a different flash pattern, could reduce or even eliminate the kills, but until people demand this, nothing will be done. I look out my window at my Scarlet Tanagers and thrill that these birds, hatched in Minnesota at least a year ago, have made at least one trip down to South America, through a maze of large cities, towers, pesticide-laden forests, and natural predators, and came all the way back again, and feel a deep sadness about the tanagers that died at this tower, after enduring the hardships and surviving so many hazards, only to die in the final stretch in such a meaningless way. You can find more information about towerkills and the US Fish and Wildlife Service’s recommendations for at least minimizing the problem at www.towerkill.com.