The northward movement of the red admiral population will cover 2,000 miles
by Bob Confer
If you’ve been outside in recent weeks you’ve no doubt encountered red admiral butterflies.
In a normal year, I might see a dozen of these beautiful insects from mid-April through May.
This year hasn’t been normal.
I’ve seen dozens of them so far, and the calendar just turned to May. I might be grossly underestimating if I say that I’ve seen 120 of them this year. On one hike the week before last, I saw twenty of them. Just yesterday, along a different trail, I saw two dozen. They’re everywhere – in woods, hedgerows, fields, and backyards.
I’m not alone in experiencing this. Many of my Facebook friends have shared observations and photos of early sightings and plentiful ones. Quite a few are saying they’ve noticed them for the first time in their lives.
Why is this happening? How did 2024 become “the year of the red admiral”?
One reason is the mildness of the past winter locally.
According to the National Weather Service, the Buffalo area’s meteorological winter saw an average temperature of 34.5, which made it the second warmest on record in Buffalo, just behind 1931-1932’s 34.6. Looking at the NWS’s Top Ten list, this past December was the second warmest all-time (39.4 degrees) and February was the warmest (34.8).
That played well to the survivability of red admirals. Some adults of this species attempt to sleepily survive our winters by hiding out under bark, in garages, and other places out of the elements. But, it’s not as easy for butterflies and months to do that than if they were pupae, snug in their silk or leaf cocoons. Only a few species are built to overwinter as adults in our northern climate (the mourning cloak butterfly being a prime example). Almost all adult red admirals die in our cold winters. An occasional one will live to see spring; you’ll see them flying around in early April. This year, many more made it out of winter alive.
Still, that accounts for only a very, very small portion of the numerous red admirals we’ve seen.
So, where have the others come from?
They migrated here.
Monarch butterflies and their migration get so much press that most people think they’re the only butterfly species that migrates and that’s what separates them from the rest and makes them so captivating.
Red admirals can hang with them as master migrators of the butterfly world.
Early every fall, in anticipation of our colder weather, the butterflies fly south, taking several generations of caterpillars, pupae, and adults to get to their wintering grounds in Alabama, Louisiana, Texas, Florida, Mexico, and Central America. Then, across multiple generations, they make their return trip to our neck of the woods in the spring. The northward movement of the red admiral population will cover 2,000 miles.
So, it’s these migrants that are most of the butterflies you’re seeing.
But, why so many this year?
Again, it’s because of the mild winter. We weren’t alone in enjoying that balmy stretch, with most of the eastern US spared any winter weather of note. Every so often, a deep freeze makes its way south – think of the Texas Deep Freeze of 2021 or recurring news stories about orange crops being threatened by frost or southern commuters unable to navigate an inch of snow. When that happens, Jack Frost’s southern vacation kills off many of the adult red admirals there. This past winter they were spared that and it’s not like the south took a beating in the winter of 2022-2023, either. That gave the red admirals two really good years to recuperate.
Adding to that is a recurring cycle of boom and bust for red admiral populations. Every ten years or so their population explodes — for reasons entomologists haven’t yet figured out. It just so happened that the most recent cycle coincided with a very warm winter (and a tame one before it), magnifying the cyclical population boom by a magnitude.
Enjoy the butterfly invasion. It’s truly a sight to behold. You never know when we’ll see the likes of it again.
