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"Record number" of raptors falling ill with West Nile virus in Colorado

Wildlife falling ill due to West Nile virus
Wildlife falling ill due to West Nile virus 02:43

Hawks and other birds of prey are falling ill, many even dying, after contracting West Nile virus in Northern Colorado. According to experts with the Rocky Mountain Raptor Program, dozens of hawks have already been rushed into their medical and rehabilitation center in June and July, with August typically being the month the majority of sick birds become ill.  

"It is a perfect storm scenario this year," said Michael Tincher, rehabilitation coordinator with RMRP. "Such an uptick in culex mosquitoes impacts especially raptors at this time of year." 

Larimer County, one of Northern Colorado's most populated regions, has reported record levels of culex mosquitoes for months now. Culex mosquitoes are the type that carry and transmit the virus. 

At one point in July, there were 10 times as many culex mosquitoes in local traps as there were in 2022.  


CBS News Colorado has covered the threat of WNV extensively since the rainy months of May and June. The increased levels of precipitation created more breeding ground for the Culex mosquitoes, spiking concerns of local health departments in Weld and Larimer counties. 

While most humans that contract the virus will never know due to minor symptoms, others will become severely ill. At least one person has already died as a result of WNV in Northern Colorado.  

But, humans are not the only ones that can fall victim of the virus. Tincher said dozens of hawks have already been brought in to his organization for medical help, many of which were ill with WNV.  

"We saw a record number of admissions (in July). 75 to be exact. Those are usually Aug. numbers," Tincher said. 

Tincher said the month of Aug. is often when most raptors are diagnosed with an illness like WNV. He predicted that they would break the record of 75 new admissions in the month of Aug.  

Most of the sick birds are young Cooper's Hawks, a species that has been blossoming in the region for decades. The birds that are most likely to get sick are the newborns that are learning to fly, therefore spending more time around the ground where mosquitoes thrive.  

"These young raptors have no immune system," Tincher said. "They spend a certain amount of time on the ground, and it puts them in the mosquito zone. They are immediately being hammered by this virus." 


Most of the raptors being rushed for medical care are spotted by members of the public. Many first notice the hawks are staying on the ground, and from there they notice other symptoms.  

Symptoms include loss of vision, brain swelling leading to grounding and confusion, and loss of critical feathers like those on their tails. Because the hawks are birds of prey, they need strong flying feathers to be able to hunt things like other birds.  

"Sometimes (a sick bird) will have extreme neurological concerns where they are having seizures," Tincher said.  

Not all birds that are on the ground are sick or wounded, though. Tincher said often times people will call in reporting a sick or wounded bird, and a simple picture or check on the bird from afar can prove they are okay to remain in the wild.  

However, Tincher said raptors that stay on the ground for a prolonged period of time should be reported to local rehabilitation centers like his. He also said birds with WNV often have a fascination with bodies of water, including swimming pools. He said if a bird is staying in or by the water and not leaving, it may be worth calling for someone to check on it.  


The RMRP, located in northern Fort Collins, cares for many types of raptors with different illnesses and injuries. While many may not survive their wounds or sicknesses, many others are brought back to full rehabilitation.  

The chronic effects of WNV can be long lasting, though. Some birds will overcome their symptoms in months. Others will take years.  

RMRP has a policy of not naming the birds they are servicing, noting that they should always be considered wild animals and not pets.

"There is no cure for a virus, it has to run its course. And a lot of birds die within 96 hours," Tincher said.  

Tincher said his team feels rewarded in their daily work, knowing they are giving back to the ecosystem they also live in. Those that recover often start in indoor cages, then are transitioned to outdoor larger enclosures before then making it to the final flying enclosure.  


Throughout the process the RMRP team tries to observe and improve their eye sight, hearing, flight capabilities and most importantly their natural instinct to hunt.

If a raptor successfully makes it through each step, the team then takes them out into open air and releases them back to the wild.  

"Hopefully we get to that day where we can take them out and release them back into the wild for their second chance at freedom," Tincher said.

One bird, simply identified as "Red Tail Hawk West Nile," obtained the virus long ago and the the program directors decided against ever attempting to release it back into the wild due to the long term health effects it has struggled with as a result. The RMRP team now uses the animal for educational purposes and also does its best to try to keep the animal the healthiest it can be.

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