NWS Captures Swarm of Butterflies on Radar, Mistakes Them for Birds

October 7, 2017 Updated: October 8, 2017

The National Weather Service in Colorado thought it was posting a picture of a swarm of birds that its radar had picked up over Denver on Tuesday, Oct. 3, when it asked the public for help in identifying them.

“Any bird experts know what kind? #ornithology,” it tweeted with a photo what looks like a blue cloud on a radar screen.

It turns out it needed a lepidopterist, someone who studies butterflies and moths.

The cloud it was seeing was a 70-mile wide swarm of butterflies.

The butterflies were painted ladies, sometimes mistaken for monarch butterflies because they have similarly black, white, and orange coloring.

A Painted Lady butterfly (Justin Sullivan/Getty Images)


The butterflies have descended on Colorado’s Front Range in recent weeks as they migrate through the Western states.

“I have been getting phone calls from people all over the Front Range in many different counties,” Butterfly Pavilion lepidopterist Sarah Garrett told The Denver Post. “Last week, I spoke to folks in North Dakota and South Dakota who have seen them. They are making their way progressively through these Western states.”

She said this atypical swarming activity is likely the result of a boomer breeding season, and not a change in habits.

The swarm started around sunrise on Tuesday and continued through the day, but hung low to the ground and out of radar detection on Wednesday, the Post reported.

A woman takes a picture at the top of Pikes Peak mountain in the Front Range of the Rocky Mountains within Pike National Forest near Springs, Colo.(Joe Klamar/AFP/Getty Images)

From NTD.tv

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