Research continues into effective black bird control

By Jennifer M. Latzke

A noisy flock of blackbirds rises up from a field, their sheer numbers blocking the sun from the sky and the sound of their wings drumming dread into a farmer's heart. For some sunflower growers in the High Plains, it's a scene much more scarier than anything Alfred Hitchcock could have ever conceived. Because, these birds aren't set on scaring a town, but rather devouring a standing crop of sunflowers and thus a grower's profits.

Each year, blackbirds cause millions of dollars of damage to agriculture. In some instances, nearly 15 percent of a sunflower field can be stripped by an industrious roost of birds--in the worst case scenario it's 100 percent crop loss. However, researchers are working on developing control methods producers can use to save their sunflowers and other crops from blackbird damage.

Dr. George M. Linz, research wildlife biologist with the U.S. Department of Agriculture-Animal Plant Health Inspection Service, is just one of the many researchers studying the blackbird situation in the High Plains. Linz, who's based at the North Dakota Field Station of the National Wildlife Research Center in Bismarck, N.D., explained that while most of his research is concentrated in the prairie pothole region of the Dakotas and parts of Canada, blackbirds can damage agricultural operations as far south as Texas and Louisiana on their annual migratory path.

Blackbirds don't restrict their diets to just sunflowers and Linz has received reports that corn is starting to feel the affects of blackbird roosts, especially where fields are planted next to sunflowers.

"Anywhere with wetland habitat in proximity is vulnerable," Linz said. "The birds will use trees to roost. They prefer late summer, early fall to use wetlands, particularly with cattails because they proved a dense habitat and protection from predators. They also like some standing water, in the cattails, to provide some warmth from the cool fall air." As for playa lakes in the southern High Plains, Linz explained that as long as vegetation is dense there is a potential for blackbirds, especially with a food source nearby.

A scary scene

When discussing blackbird damage, it's important to understand that it's not just a matter of a few hundred birds setting up home in a sunflower field, annoying neighbors and snacking on seeds. Most roosts, according to Linz, can number around 100,000. "The largest group I've seen, in the fall, is 500,000," he said. All those roosts can add up to about 700 million blackbirds that spend their summer months in the north and migrate to the south in the fall.

With numbers like that, all it takes is one roost to settle in a sunflower field to do some serious damage to a farmer's bottom line.

"I worked in a field this past year in North Dakota, where we had been planting wildlife conservation plots to lure birds to small plantings of about 20 acres," Linz said. He told of one 20-acre plot next to a farmer's 100-acre sunflower field that was completely wiped out by the birds. "The birds just wiped out another 70 to 100 acres of the field next to the plot," he said. "He had over a section, and had a good crop on the rest of it, but blackbirds can really hurt you bad. Typically we're looking at 15 percent of the growers will have a problem with more than 5 percent of their field lost to blackbirds." The rest of the industry may have minimal bird damage but it's not enough to cause them to stop planting sunflowers, Linz added.

"The number one reason growers stop growing sunflowers is that they get a crop through the drought, diseases, insects and more and it's just about ready to put in their bins and then here comes the blackbirds to do their damage," Linz said. "Just seeing the birds has a real perception of damage to growers, even if they aren't doing that much harm to a field, too."

Available food sources

The fall months in the Dakotas are the worst period for sunflower damage from blackbirds, Linz said. "In the fall they're putting on their pre-migratory fat," he said. "The worst period of time for sunflowers is the first three to four weeks after the seed starts forming. In the northern Great Plains, that would roughly be the third to fourth week of August, to mid-September. With corn, it's earlier and it's most vulnerable when it's in the milk stage in July."

Blackbirds are feathery opportunists--they'll feed on all sorts of crop and weed seeds. And since corn is becoming more profitable to grow in the Dakotas for its ethanol potential, there's more fields of it being grown. "If you put mature corn next to mature sunflowers, the birds will choose sunflowers every time," Linz said. However, since the corn growth cycle is earlier than sunflowers, it reaches a palatability point before sunflowers have matured and blackbirds will flock to this available food source.

"After corn hardens up, just as the sunflowers come on, we see blackbirds moving from corn to sunflowers," Linz said. "We'll see birds in corn fields if we're chasing them out of sunflower fields, though. And, with Roundup Ready corn, there's not much weed seed available to them and there's not much else to eat but the kernels of corn."

Linz called this "short-stopping," where the available food sources will cause the birds to linger longer in one place before migrating on. And, because blackbirds will eat just about any crop, their damage can cover the wide spectrum of agricultural crops through the High Plains.

As the blackbirds migrate, they'll fly down through Nebraska, Kansas and Oklahoma--feeding in fields and feedlots along the way--and winter in Texas, Arkansas and Louisiana.

"They'll feed on rice and waste grain in the fields," Linz said. "Unfortunately, for the rice grower, in the spring, when they're putting out rice, the birds will pull up the sprouting rice. Then, as the rice crop grows, the blackbirds will move back north and breed up here and do their damage along the way."

Non-lethal control methods

Rotations can only do so much to control blackbirds, Linz said. With the emerging ethanol market, farmers are hard pressed to justify juggling their field choices around the habitats of wild birds. But, common sense must be used in planting decisions, Linz explained.

"Farmers should move away from areas traditionally habitats for blackbirds," he said. "It's price driven, but we find as producers start to edge their fields closer to bird areas we tend to hear more from growers who are having bird problems."

The non-lethal approach, and the first step Linz suggests growers take, is to manage the potential habitat of blackbirds, without taking a "scorched Earth" policy and decimating environmental resources.

"There are cost share programs in place that will cover up to 70 percent of the costs of habitat management," Linz said. By using aquatic versions of glyphosate to control cattails, a grower could kill over 60 percent of the blackbirds habitat and still leave enough for other wildlife to use as cover, Linz said.

It's vital, though, that growers work with their neighbors in controlling potential habitats for blackbirds, Linz said. Afterall, blackbirds don't recognize property lines when they're on the hunt for dinner.

A secondary control measure that is a little more expensive for growers, is to plant 20-acre conservation plots near sunflower fields. "There's not 100 percent control, because the blackbirds will eat weeds with sunflower seeds in the plots, but we've seen over 60 species of birds use these plots besides the blackbirds," Linz said. Conservation plots can serve to lure the blackbirds from a commercial sunflower field and provide habitat for other wildlife in the long run.

A third control method, which is about to come online, is an application of Roundup on sunflowers to kill the sunflower crop so that it can be harvested earlier, before the blackbirds have a chance to feast upon it. The Environmental Protection Agency, according to Linz, is about to approve this new use for Roundup.

"Growers can spray sunflowers at about 50 percent moisture without losing their yield or oil," he said. "This can move up harvest from 10 days to a couple of weeks and allow the grower to get the crop off before the big migratory flocks come in from Canada." This new method was researched by North Dakota State University scientists, he added. "Compared to losing seed to shattering, or loss to birds or weather, it's really inexpensive in the long run to growers," Linz said.

Lethal control methods

It's important to note that there are depredation orders in regards to shooting blackbirds that are or are about to do damage to a field, which means a grower can kill birds caught in the act. The only time a grower can't shoot blackbirds is during the breeding season of May through June. Linz said it would take a lot of shooting, though, to drive off blackbird roosts.

"They can also use propane cannons, but they work best in conjunction with shotgun shooting," Linz said. "With just cannons, it takes them a short time to figure out the noise won't hurt them." With growing farm size, though, many fields are spread out over long distances and it's difficult for growers to be on hand regularly to shoot blackbirds when necessary.

Setting up bait trays and decoy traps is another lethal control method growers have used in the past, but it's difficult to use avicides to control only blackbirds and not harm other bird species just passing through the area.

"You have to be able to use them without affecting mourning doves and pheasants," Linz said. These two species are vital to the hunting industry in the Plains states. Also, migratory song birds are protected by international treaties and so any method targeted at killing blackbirds must not affect innocent song birds, Linz said.

Linz suggests producers should use an integrated approach to managing blackbirds.

"If I've learned one thing over 25 years working on blackbirds, it's that I'm amazed at how adaptable these birds are," Linz said. "They will move with the crop, so if it shifts east or west the birds will move east or west."

By using a mixture of habitat control, early harvest aids, and in some extreme instances lethal control methods, growers can ensure that their sunflower fields don't fall victim to marauding blackbirds.

Jennifer M. Latzke can be reached by phone at 620-227-1807, or by e-mail at jlatzke@hpj.com.

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Date: 3/8/07

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