Red Admirals Arrive Early in Central Iowa

I spotted the first Red Admirals of the season in Ames, Iowa on March 30 – the earliest arrival date since 2012. On this sunny early afternoon, I was walking along a path in the woods behind our house, on the way to check two wildlife cameras, when I spotted the first of them basking on a bed of leaves. After watching and photographing it for some minutes, I continued along the path and then uphill toward the fox den that we were monitoring. While I was changing the batteries in the cameras, there was a dark brown flash – another Red Admiral, several times landing and flying short hops before disappearing to the northeast.

Upon returning to the initial spot, there was yet another Red Admiral with more wing wear than the first one. This butterfly seemed to be perching and patrolling the area. Finally, I saw a fourth Red Admiral in migratory straight-line flight toward the northeast.

These butterflies arrived shortly after a tongue of warm, moist air flowed toward us from the south. This raises the question of whether Red Admirals had been moving gradually northward during the past several weeks, or whether instead they had come abruptly northward for a long distance within just a few days. A series of first-of-season sightings along the migratory route therefore would be interesting.

Have Red Admirals actually been arriving here earlier in more recent years? Statistically, no – not yet anyway. First arrival times here typically vary widely from early April to mid-May with no definite trend in either direction. Even so, our unusually warm winter had me wondering if they might arrive early this year. Stinging nettles have also been sprouting earlier this year, so the new arrivals should not lack for larval food plants.

Whether or not they are arriving earlier, another possibility is that they might be overwintering farther north in recent years in response to the warming climate.

Posted on April 3, 2024 04:09 AM by iowabiologist