A vulture conundrum...

A local power plant here in NE OK has long been plagued with Black Vultures (Coragyps atratus) roosting on the steel structure over their boilers. Their numbers conservatively estimated at 450-500 individuals. Their droppings were a problem as they created smell, discoloration, and corrosion of the steel structure as well as a health risk to the employees. In March/April 2025, Predator Impact was contracted for an experimental project to determine if the vulture population could be dispersed using non-lethal methods. 

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BACKGROUND

The Black Vulture (Coragyps atratus) is a common bird throughout its range. Northeast Oklahoma is at the northern edge of their normal range. 
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https://www.allaboutbirds.org/guide/Black_Vulture/maps-range

Black Vultures are resident year-round and will only migrate short distances if at all. This explains the year-round presence at the powerplant.
They are highly gregarious birds and will often roost in large numbers.
The Black Vultures have a relatively poor sense of smell. Their primary means of finding the carrion upon which they feed is to follow the Turkey Vultures (Cathartes aura) which have an excellent sense of smell. While the Turkey Vulture is slightly larger, the Black Vultures travel in packs, overwhelm the larger Turkey Vulture with numbers and often steal the carcass. A few Turkey Vultures have been observed roosting with the Black Vultures at the powerplant.
The vulture droppings are vile smelling, highly acidic, and leave a chalky white residue from the bones they digest. At roost sites, their droppings can become a nuisance. Fortunately, their strong stomach acid kills any diseases in the carcasses they feed on, however there are a few diseases spread by all bird droppings including Black Vulture droppings.
These include:

• Histoplasmosis
• Salmonellosis
• Psittacosis (ornithosis)
• Cryptococcosis (rare)
• Avian Influenza

Their droppings are very acidic and when accumulated in large numbers, there is a possibility of corrosion damage to steel structures.
Both Black and Turkey Vultures are poor fliers. They travel long distances in search of carrion but prefer to soar rather than flap. This requires lift from warm air rising called thermals. This can be air rising over a sun warmed field, black roofs or parking lots, or as is the case at this powerplant, warm air rising from the cooling towers.

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ABATEMENT OPTIONS

In speaking with other wildlife professionals and researching the literature, it was clear that preventing the vultures from roosting, or “roost busting”, was the best chance for success in convincing them to leave the area. By denying them a calm, peaceful place to sleep, they should move to another location. This is a common (and very successful) technique used to move large populations of grackles and other blackbirds. It seemed logical that it would be effective against Black Vultures.
It is possible to receive a federal permit to kill up to 10 vultures, but this was deemed to be too few to have any real effect and the paperwork is daunting. Only non-lethal methods were considered. 
​There are numerous non-lethal ways to discourage roosting.

• Lasers- Certain frequencies of lasers terrify blackbirds, geese, and herons. It was not known if the same frequencies will work for vultures but deemed worth testing. The lasers selected were commercially available handheld CLASSIIIa 532nm <5mW green lasers.

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• Drones- Drone harassment is very effective against geese. There is no history in the literature of its use against vultures. Predator Impact employs a FAA licensed drone pilot, and it was decided to test the effect of the drone on the vultures.
• Noisemakers- Loud noises startle them and disrupt sleep. The most common noisemaker is the “Birdbanger”. It fires a projectile similar to a “chaser” firework with a loud report at the end. The presence of large quantities of flammable coal made the use of all pyrotechnic devices too risky and was disregarded.
• Paintball- Paintball can be a very effective frightening device. It is crucial that you never hit the vulture with a paintball. Their bones are delicate and break easily, but the noise of the gun, impact of the paintball hitting nearby, and the splatter are all good deterrents.
• Dogs- When the vultures are on the ground, trained dogs are effective. Again, the dogs cannot legally touch the vultures, but the running and barking may cause them to leave. 
• Methyl Anthranilate- Methyl Anthranilate (MA) is a big name for the flavoring in grape Kool Aide. First isolated from Concorde grapes, MA is harmless to mammals and fish but causes discomfort in birds. It is sprayed on grass to deter geese from feeding. When geese eat it, they experience “digestive discomfort” and avoid the area. There is some research into using a mister to distribute a MA mist to deter vultures roosting, but it is not mature enough for serious consideration.
• Birdspikes- Birdspikes are strips of stainless-steel spikes that prevent birds from perching.​

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• While highly effective, the sheer volume of birdspikes required to cover the structure above and around the boilers, and the cost and difficulty of installing them at this height, was prohibitive. 
• Effigies- There are many references in the literature of technicians hanging dead vultures, or stuffed decoys that look like a dead vulture, near roosts to deter roosting.

        

           https://www.wildlifecontrolsupplies.com/animal/FF-VE-001.html

• This will be considered, but the best places to install them will involve leaving the catwalks and accessing the high steel areas.​​

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• Falconry based abatement- Predator Impact maintains trained Harris’ hawks for the purpose of roost busting blackbirds.
  ​Due to the heights required to work the hawks, the risk of flying in an open steel structure and the unknown efficacy of hawks against vultures, this option was not seriously considered.

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​INITIAL TEST
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Before starting a formal project, it was decided to do a one evening test to get a general idea if roost busting would work on this population.
Several years ago, we did an abatement job on a roost of herons in Oklahoma City. The project was not successful, but there was a small roost of Turkey Vultures that stayed in the area looking for dead herons and chicks. When the lasers we were using to frighten the herons got close to the Turkey vultures, they reacted with panic. Based on this very limited information, we decided to try the laser first.

Monday 3-Feb 2025, Predator Impact and a representative of the powerplant were on the highest walkway above the boilers just as the sun began to set. A quick estimate counted about 450 Black Vultures and a few Turkey Vultures perched on the iron works above the boilers, or soaring above preparing to land.

​There are approximately 200 vultures visible in this one picture. Less than half of the total present. 

​After about 20 minutes of harassing the vultures with the laser, the site was completely clean. 
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​As the vultures left, they predominantly flew East. It is reasonable to assume that there was a pre-established alternate roost somewhere in that direction.
We stayed on site until it was completely dark and there were no vultures on the site when we left. 
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The vultures’ response was very positive. Even though the majority of the vultures returned in the following days, it was decided that the test was successful enough to warrant a full-scale abatement project with the understanding that the project was an experiment with unpredictable results.

​The first day of abatement was 20-Mar 2025. 

ABATEMENT
Laser harassment is the simplest and potentially the most effective of the different abatement tools, therefore it was decided to start with the laser and add additional treatments as warranted. Each day the number of vultures present on the site would be estimated and recorded before laser harassment.
The lasers were used from as high a vantage point as possible, or against a solid backstop to minimize the laser exposure above the facility.

After the second night of treatment, the estimated population was reduced by about 50%.
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On 22-Mar 2025, we brought in our FAA certified drone pilot and a DJI Phantom 4 Quadcopter drone to test drone harassment on the vultures. 

Before flying the drone near the boilers, we tested it on a group of vultures perching on some surplus equipment in the area. 
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​Unfortunately, the drone proved to have a minimal impact on the vultures. When it got close to them, they would casually move to another perch nearby, but there was not the expected fear response we were hoping to receive. No further drone harassment was performed. 

Likewise, the trained harassment dogs had a similar effect. 

While the dogs chased the vultures enthusiastically while the vultures were on the ground, the vultures just moved to a perch out of the dog’s reach and then ignored them.

We continued the laser harassment and the day-over-day reduction in the population continued. After a week, there were about a dozen vultures that persisted in trying to perch on one of the boilers. There is some structure there that they could hide behind to avoid the laser. We brought in a paintball gun with clear paintballs. The paintballs were deliberately shot to hit the metal structure near the vultures, but the vultures were never contacted. The sharp noise of the gun firing rapidly, the sound of the paintballs hitting the steel structure, and the splatter of the paintballs proved to be the final factor in denying the vultures a roosting site.

All vultures abandoned the property.

We continued to monitor the site, but while there were a few vultures overhead looking for lift from the cooling towers, there were no more vultures roosting anywhere on site.

Project concluded 17-Apr 2025. 

CONCLUSION
The combination of the laser and paintball proved to be an effective combination and completely eliminated any vultures roosting on site.
It is unknown if there will be more vultures returning in the future, but if so, the process can be repeated.
As of the time of this writing, a month has passed and there continue to be a few vultures soaring over the site looking for lift from the cooling towers, but there have been no instances of them using the structure to roost again. 

Got a problem with vultures, or other birds roosting on your property? Call Predator Impact for a free, no obligation consultation. We are always up for a new challenge! 

Predator Impact
​(918) 397-4091