Those large flocks of birds on your dairy farm are not only a nuisance; they are affecting your bottom line.

Wildlife biologist with USDA Wildlife Services Ernie Colboth says 1,000 starlings consume 10 pounds of dairy feed in about 10 minutes on one farm – which is about 900 pounds of feed in a week. He says it is not uncommon for a dairy farm to have several thousand birds.

He adds, “What they don’t eat, they contaminate, and the cows don’t like to eat that.”

Birds on a dairy tend to eat the expensive grain, fats, protein and supplements from dairy rations, which results in a decrease in milk production, less weight gain and property damage.

There is also the risk of disease transmission to livestock and humans, with salmonella and E. coli being two of the most common. They are also known to carry Johne’s disease, toxoplasmosis, cryptococcosis, candidiasis, aspergillosis, meningitis and listeriosis. When birds roost in the barn, there is also a higher risk of disease transmission because their feces fall from the nests onto the cows, feed and water, but they can also transmit disease by having their own fecal matter on their feet, legs and feathers, and then touching feed and water.

If you have any of these illnesses on your operation, talk to your veterinarian if birds could be a contributing cause.

Two starlings will have three to four nest sittings in a summer, each with five to six young, so a small flock can become a flock of thousands in a short time.

Starlings are non-native invasive birds, and they are not protected in any state or by federal law. The small, chunky bird is a dark color, a green/purple iridescent. They will flock in groups of 100 to 10,000 birds, and the North American population is considered to be more than 200 million. Starlings can be found in the 48 contiguous states, although damage is most prevalent in the Midwest.

Colboth cited data from 2012 that said dairies with flocks of 10,000 starlings pay an additional $2.07 per hundredweight of milk, and farms with 1,000 to 10,000 starlings pay about an extra dollar per hundredweight of milk.

Habitat modification, exclusion, harassment, trapping and avicides are ways to control starlings.

Colboth recommends when creating building plans to include the use of wire cloth or wire screen to exclude birds, although a determined flock of starlings can often figure out a way around exclusion methods. If you choose to try this, pay special attention to the roof ridge cap and the soffit areas of your buildings.

Harassment methods tend to be very time-consuming. “It's just not feasible when dealing with large numbers of starlings,” Colboth says.

Trapping consists of “one-way” designs and can be homemade or purchased, but trapping 100 birds a day will not get you very far if you have several thousand birds. Birds are baited with bread, dog food, grain or a protein, or fat pellets. Traps are easy to maintain and safe for all other species. It takes a lot of effort with this method, but Colboth says, “It is an option, and it does work.”

Wildlife Services follows the recommendations of the American Veterinary Medical Association (AVMA) guidelines on euthanasia for birds caught in traps. Carcasses are properly disposed of according to all federal, state and local regulations, he says.

Avicides that are available for use on-farm include Avitrol and Starlicide, but he says they do need to eat quite a bit of it to make it work.

Colboth says the most effective avicide is DRC-1339, which is authorized for use by the USDA only. “It can knock 5,000 birds down to 500 birds with just one treatment, which can make a world of difference.”

DRC-1339 is a metabolized poison, which means other animals will not be poisoned if they eat the dead starlings. Mammals and raptors are generally resistant to it, but starlings are very sensitive to it. They will start to show physical signs of poisoning in four to eight hours (sluggish, not able to fly), and it is lethal in 24 to 48 hours. If they eat the poison in the morning, they will most often die that night while roosting. Only a few tablespoons are needed to kill large flocks. 

Colboth says the most important step when using DRC-1339 is pre-baiting. For several days, the starlings should be baited in an area where they usually feed. He suggests using a supplemental nugget with a fat content of 20% to 50% and crude protein of 10% to 15%.

Often, the baiting area is in a feed alley or near silage storage, but there is no risk to the cows’ safety.

The dairy producer should watch how the birds move around during the day and put out pre-bait in a regularly used area for three to five days, and it works best if the weather forecast is similar for those few days. Make sure the birds are eating the bait, and that other birds such as songbirds aren’t eating the bait.

The bait should be placed out as early as possible and available all day long. He says putting it out “fresh” prior to their usual feeding time works best.

Once good bait acceptance is established and no precipitation is forecast, the “hot bait” can be put out. He says generally cold weather with snow cover works best and when the weather is consistent to the times the pre-bait has been out.

The USDA does notify department of natural resources (DNR) wildlife, conservation officers, local law enforcement and public health in the area the baiting will take place, to avoid panic if large flocks of dead birds are found. Local neighbors should also be notified.

Colboth’s office is in Iowa, and he says he is busiest when starlings are flocked up, generally September to March.

The USDA Wildlife Services can help dairy producers deal with starlings. There is a cost of $500 to $1,000 for the on-site work through the USDA, and costs are on the lower end if several dairy producers in the same area contact the USDA at the same time. Colboth says there is a USDA Wildlife Services office in all 50 states. Contact information for each state can be found on the Wildlife Services website or call toll free (866) 487-3297.