Large populations of black birds make a temporary home for themselves somewhere in the Delta each year, and each year the folks with USDA's Wildlife Services field numerous calls from disgruntled citizens.
In addition to being a general noisy nuisance, large blackbird populations can bring with them an intense ammonia smell and a potential increased risk to human health and safety.
Deltans often begin seeing the migratory birds in November, with heavier concentrations moving in sometime in December and staying until mid-March or early April if the temperatures remain unseasonable chilly.
“They've been coming here for 100 years, and you can bet they'll come back next year. The earlier in the season roost dispersal is attempted, the better,” says Seth Swafford, a wildlife biologist, with USDA's Wildlife Service in Stoneville, Miss.
The flocks of blackbirds that make their home in the Mid-South are generally comprised of several different species of birds, including blackbirds, red-winged blackbirds, brown-headed cowbirds, and European starlings. American robins can also be present in the flock. “American robins are the most difficult to disperse because they are persistent, and don't scare off as well. They are less likely to be frightened by noise-making devices,” Swafford says.
After a USDA biologist completes a site survey to assess the extent of the problem, getting rid of large bird roosts can often be accomplished with non-lethal methods of harassment.
“Ideally, we would like to see municipality governments get involved in the removal of blackbird roosts. What is absolutely required is a group of people working together to disperse the roost. It must be a team approach. You can't have too many people, and you can't shoot too many pyrotechnics.”
Similar to a firecracker, pyrotechnics frighten the birds by launching noise in the direction of the roosting birds. “That's preferable to a shotgun blast where the noise remains, for the most part, on the ground with the gun,” Swafford says.
Next in Stafford's arsenal, is a propane cannon, which is the same device used to disperse predatory birds roosting near catfish ponds.
Often, though, the most low-tech of devices can serve the purpose. Any obscene noise-making device, including air horns, or even the banging together of metal trash can lids can be used to convince the birds to move on to less-populated areas, like pecan orchards or wooded areas. Sirens on police cars can also be extremely effective.
What is important, Swafford says, is that the noise-making continue for a minimum of three consecutive evenings and preferably for five evenings, starting when the birds arrive to roost in the afternoon, and commencing at dark. “If the effect hasn't taken place in five days it generally won't work, and we'll have to move to alternative control measures. No one technique is a silver bullet, though, and we've got to use a combination of things to scare these birds away from an area,” he says.
Once scared away, the problem birds usually remove themselves from that location until the next year, and often don't reappear in the same area for several years.
The birds are attracted to more urban locations in the Delta for one reason, and that's shelter. Landscaped yards in many Delta neighborhoods offer blackbirds a safe, comfortable winter home in magnolias, live oaks, holly shrubs and bushes.
“They come into the thick canopy type of these trees and shrubs for protection, then leave in the morning headed towards nearby crop fields for feed, and then return again for shelter in the afternoon,” Swafford says. “You can make the trees in your neighborhood less attractive to these birds by thinning tree limbs, which maintains the integrity of the tree while reducing the amount of available roosting area.”