Afton State Park phenology, March 29 to April 4

Herons and eagles return to old nesting grounds, as frogs and flowers begin to stir.




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Canada geese on the St. Croix River ice at Afton State Park. (sls42/iNaturalist)

Note from the naturalist: “Hope you enjoy this week’s phenology update. We will be making eclipse viewers this weekend in preparation for the April 8th event. Join us at 10 a.m. on Saturday March 30 to make your own simple eclipse viewer.”


On Thursday the 29th get up early and look for brilliant Venus low in the western sky. Above Venus you will see the planet Saturn, and above Saturn the planet Mars. Mars will be much dimmer than Saturn. Saturn will be halfway between Venus and Mars which may make Mars easier to find.


Great Blue Herons returned to this area as soon as there was open water. Have you seen any? Other members of the Heron family, including Great Egrets, Green Herons, and Black-crowned Night Herons, also return as waters open up and they are able to hunt for frogs and fish. Look for them along the river and along Trout Brook.

Eagles are one of the first birds to nest, often laying eggs in mid-February. They build big nests of sticks, and use them year after year, each year adding on to make the nest even bigger. You’ll often see the nests in cottonwood trees. Cottonwoods are strong enough to hold the nests, which can weigh up to a ton! Eagle eggs hatch after about a month of incubation. Both parents participate in feeding the hatchlings and protecting the nest. If you are lucky enough to see an eagle’s nest, be respectful and observe it from a distance using binoculars.

Amphibians and Reptiles

Spring peepers and boreal chorus frogs continue calling in the evenings. Wood Frogs join the frog chorus in early April. If you are walking through a wooded area with ponds and hear low chuckling that suddenly stops when you get close to it, you’re hearing wood frogs! Wood Frogs can sense the vibrations of your footsteps and think you might be a frog-eating animal, which is why they go silent. If you stand still for a few moments they will resume their chuckling. Peepers and Chorus Frogs are both about one inch long, while Wood Frogs can be much bigger, ranging from one to three inches long.


Hepatica leaves are poking up from under the leaf litter. Hepaticas are usually the first of the spring ephemeral wildflowers to bloom. They are called “hepatica” because their three-lobed leaves are shaped like a liver – “hepar” means “liver” in Greek. Bloodroots also bloom very early. Bloodroot takes its name from its reddish-orange stems that extend underground, and its blood-red colored sap. These two “spring ephemerals” and others live in the hardwood forests and bloom before the trees have leafed out, when sunlight reaches the forest floor. Look for them in the woods at Afton.


Aspen trees have bloomed, and the fuzzy catkins blow down onto the ground in the wind and rain. Aspen trees drop their leaves in the fall, but you may find some on the ground near the trees.

Weather observations

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

Friday, March 292023: teens in the morning, with high temperature below freezing; 2021: 70° and very windy
Saturday, March 302022: rain, ice and snow overnight
Sunday, March 312023: Gray day, with spitty rain off and on; 2018: One inch of wet snow overnight
Monday, April 12023: Blizzard overnight, 20s, 8 inches of heavy, wet, snow by morning; 2015: record high of 84°; 2002: record snowfall of 4.6 inches
Tuesday, April 22023: the end of a record streak of 132 days with the
temperature below 50 degrees; 2020: pleasant
morning, temperature near 40°; 2006: record rainfall
of 1.06 inches
Wednesday, April 32021: lovely day in 70s; 2020: rain and snow off and
on throughout day; 2018: record snowfall of 7.5
Thursday, April 42022: ½ inch of wet snow overnight; 2021: record high of 85°; 2020: cold overnight, in the 20s in the morning

Photo/Image credits

All photos/images copyright Nina Manzi, except:

  • Dean Lokken: Great Egret
  • Gary Sater: Bald Eagles, Great Blue Heron, Green Heron
  • Allen Blake Sheldon, MN Conservation Volunteer: Boreal Chorus Frog, Spring Peeper




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Afton State Park phenology, March 29 to April 4