Afton State Park phenology, week of April 10, 2020

Wildlife to look for as spring progresses in the St. Croix Valley.




3 minute read

Spring Peeper (Photo by Brian Gratwicke, Flickr)

Afton State Park volunteer Nina Manzi has been updating the phenology calendar in the visitor center with events and pictures for years. Since the visitor center has been closed and visitors haven’t been able to check the phenology calendar to see what signs of spring to look for, Nina is sending it online.

Phenology is the study of recurring events in the life cycle of plants and animals, many of which are closely tied to patterns of climate and seasonality. Learn more at the Minnesota Phenology Network.


On Wednesday the 15th, get up early and look in the eastern sky. Above the moon you’ll see Mars to the left, then Saturn and Jupiter. Jupiter will be the brighter of the two.


Female red-winged blackbird. (Photo by Rodney Campbell, Flickr)

Many bird species that migrate south for the winter have returned to Minnesota and Afton State Park.

These include eastern bluebirds, American robins, hooded mergansers, and red-winged blackbirds. The male red-wingeds arrived a couple of weeks ago to claim territories; the females should be here any time.

Watch for great blue herons and great egrets overhead and along water. Watch for meadowlarks, bobolinks, tree swallows, barn swallows, and turkey vultures to arrive soon.

Nest-building should be underway this week, and it’s also a good time to look for last-year’s nest in trees that haven’t yet leafed out.


As the days grow warmer the mid-sized mammals, which aren’t true hibernators, become more active. Look for raccoons, opossums, and woodchucks on warm days.

Amphibians and reptiles

In the early evening listen for the calling of western chorus frogs, wood frogs, and possibly spring peepers; they began calling in early April.

Chorus frogs sound like you are running your finger over a comb, wood frogs make a low chuckling sound. Tree frogs will start calling soon; they make a very loud trilling sound that many people mistake for a bird. You may also see fox snakes and garter snakes basking in the sun on warm days.


On sunny days there is always a good chance of seeing a mourning cloak butterfly. They overwinter as adults and are often the first butterfly we see in the springtime.


Hepatica (Greg Seitz, St. Croix 360)

Spring ephemeral wildflowers begin blooming in the woodlands. They’re called “ephemerals” because they only bloom for a short time. (Editor’s note: Spring ephemerals are technically only flowers which complete their life cycle — flower, leaf-out, set fruit, store root energy — before the tree canopy closes, but the term is often used to include other early bloomers.)

Look for them anywhere under trees at Afton; they’re especially prevalent along the trail that borders Afton Alps ski area.

Also look for fuzzy aspen catkins on trees and blown down to the ground after rains.

Weather observations

Here are some weather observations for this week from past years.

Friday, April 101996: 65° at 1:00 p.m.
Sunday, April 121997: St. Croix flooding, only one step out of water at lower picnic area
Monday, April 132006: record high of 84°
Tuesday, April 142003: record high of 89°
Wednesday, April 152002: record high of 91°
2004: record low of 18°
2012: record rainfall of 1.19”
Thursday, April 162003: record rainfall of 1.04”