Monday, March 19, 2007

Blackening the sky

As the shots rang out, I immediately pulled over. I thought I had blown a tire. Looking to my left on Dunklin County's Highway 61 was a USDA official shooting shotgun blanks into the trees next to the road. For the past several years, the USDA's Delta Research Center-Animal Damage Unit has tried various methods to stop large flocks of red-winged blackbirds from roosting in the county's residential area. The county has no trees except in front of a few businesses and homes. These trees invite flocks of almost 1 million birds to roost and deposit large amounts of guano, which negatively impacts the health of Dunklin Co. citizens.

The Animal Damage Unit began their research several years ago to determine how much crop damage was caused by blackbirds. Thousands of birds were killed in the early days of the project; feeding behavior and gut contents were examined. It was discovered that blackbirds didn't eat nearly as much rice, corn or soy as the researchers and farmers had originally thought. Weed seeds made up the bulk of their diet. But the blackbird guano caused serious depradation of crop quality. Local citizens began complaining that even though the birds were not eating crops, guano deposits were causing respiratory disorders. Now, when home or business owners discover a roosting flock in the area, the Animal Damage Unit is called to shoot blanks, firecrackers or small cannons to deter the birds from staying in one place. Researchers have learned that the birds have become accustomed to the loud blasts. Farmers in the area have resorted to poisoning their fields on occasion, but the state conservation commission penalizes farmers who do this. The latest technique to stop birds from roosting in local communities remains a vague mystery to me. Large cotton trailers baited with food are placed in fields. To access the food, the birds have to fly through a tunnel. Like a minnow trap, the funnel allows the birds to get in but they cannot escape. The agent would not tell me what happens to the birds once they are trapped in the cotton trailer.

Blackbird numbers are declining at a rate of 2.1% each year. Because blackbird flocks are so large and often mixed with grackles, cowbirds and starlings, many people haven't really noticed the general decline in the birds. Red-winged blackbirds remain the most common bird in North America; their numbers in the mid 1990s hovered around 180 million individuals. They belong to the Icteridae family which includes meadowlarks, bobolinks and American orioles. The birds in this family exhibit a remarkable foraging adaptation called "gaping." The skull of an icterid is formed to allow the bird to open the beak powerfully to force open holes in fruit, bark, soil and other substrates to expose food. Red-winged blackbirds use gaping techniques to open sedge stems to expose prey. Most icterids are long billed and have relatively short, deep wings which allow for rapid lifting.

Blackbird flocks are everywhere. Peter sees huge flocks in his Roman neighborhood of Trastevere. My mother's dogs hover under the bushes when the blackbirds descend on the backyard. Thousands of them roost in various parts of the park, always forcing me to go birding elsewhere. Maybe if a handful of trees were spared during the deforestation of southeast Missouri, the blackbirds wouldn't have to congregate in a three block area in Dunklin County.

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