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.
https://twitter.com/NWSBoulder/status/915274142341042178
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.
https://twitter.com/NWSBoulder/status/915631476393246722
https://twitter.com/NWSBoulder/status/915631590289690624
https://twitter.com/NWSBoulder/status/915631757667467264
https://twitter.com/NWSBoulder/status/915632088950468608
The butterflies have descended on Colorado’s Front Range in recent weeks as they migrate through the Western states.
She said this atypical swarming activity is likely the result of a boomer breeding season, and not a change in habits.
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