Afton State Park phenology April 28 to May 4

Birds nesting, frogs singing, and fleeting flowers blooming.




3 minute read

Round-lobed hepatica (Greg Seitz/St. Croix 360)


Venus is very high and bright in the western sky after sunset. On Thursday May 4th get up before sunrise and look in the southeastern sky for the Eta Aquarid meteor shower.


White-throated sparrows continue to move through our area heading farther north, singing “Old Sam Peabody Peabody”. White-throated Sparrows have striped caps and a white patch on their throats. They look very similar to White-crowned Sparrows, which don’t have the white throat patch.

Chipping Sparrows, which have returned to our area, look quite a bit different – you can identify them by their rusty-red caps.

Eastern Kingbirds are back, too. They have a white band at the end of their tails, and are excellent flycatchers. They sit on a perch and watch for insects, then hover in the air when they fly after them. Swooping out from a perch to catch an insect is called “sallying”.

American Goldfinches are growing new yellow feathers for the summer season, replacing the gray feathers they wore in winter.

And remember listening to Great-horned owls duet hooting back in January and February when they were nesting and laying eggs? The young owlets have hatched and the juveniles are leaving the nests, but that doesn’t mean they’re on their own. The owlets remain with their parents until fall as they learn how to hunt for themselves. One of the animals they sometimes hunt is the skunk. Like most birds owls cannot smell very well, making the skunk’s spray ineffective against them.

Amphibians and Reptiles

Chorus Frogs continue calling, and the Northern Leopard Frogs have joined in. Male Leopard frogs make a low, guttural snoring sound that last two to four seconds. And in early May the tree frogs and toads start calling, too. There are two species of tree frogs at Afton, the Gray Tree Frog and the Cope’s Gray Tree Frog. Both of them can change color from green to gray, and both have yellow patches on the inside of their hind legs. It is hard to tell the two tree frog species apart without hearing their calls, and even then it’s not easy! Both make a very loud trilling call that lasts one to three seconds. People often think they are hearing a bird. The Cope’s Gray Tree Frog’s call is slightly higher-pitched and a little faster than the Gray Tree Frog’s call. The American Toad makes a high-pitched trilling call that goes on for ten to 30 seconds, often with several toads calling at once.


Butterflies are not the only insects to migrate! Last fall juvenile Green Darner Dragonflies flew south, and the offspring of those dragonflies are flying north this spring. They will be the first dragonflies we see here in Minnesota in spring.

Tiger Swallowtail butterflies don’t migrate. They overwinter as pupae with the adult butterflies emerging in late April or early May. Male Tiger Swallowtails are always yellow in color; females may be yellow or black. The black females are uncommon in Minnesota; you are more likely to see them if you travel south.


This is our second cool spring in a row, and once again the blooming of spring ephemerals is happening nearly three weeks later than in recent years. This week look in the woods for Hepatica, Bloodroot, and Dutchman’s Breeches.


Some of the Aspen trees are just blooming now, as happened last year; two years ago they bloomed in early April! The fuzzy catkins blow down onto the ground in the wind and rain. Aspen trees drop their leaves in fall, but you may find some around them on the ground.

Weather observations

Here are some weather observations from the Afton State Park area from past years.

Here’s a photo of the stairs at the lower picnic area during the flood of 2001. How high will the St. Croix go this year??
Friday, April 282020: rain off and on from morning through afternoon; 2004: record high of 91°
Saturday, April 292022: in the 50s; 2020: 1” of rain
Sunday, April 302022,2019, and 2017: rain off and on through the day
Monday, May 12022: 40s, light rain through day; 2021: high in the 80s
Tuesday, May 22019: gray and in the 40s through the day
Wednesday, May 32022 and 2020: sunny and pleasant, in the high 60s; 2013: record snowfall of one-half inch
Thursday, May 42019: sunny and near 70°

Photo/Image credits

All photos copyright Nina Manzi, except:

  • Dean Lokken: Eastern Kingbird, Northern Leopard Frog
  • Nathan Pasch, University of Minnesota College of Veterinary Science: Great horned owl nest and egg illustration
  • Gary Sater: American Goldfinch, Great Horned Owl juvenile, dark form of Tiger Swallowtail
  • Tammy Wolfe, MN Conservation Volunteer: Great Horned Owl adult and juvenile