Afton State Park phenology, April 17 to 23

Many migratory birds are making their way back to the St. Croix Valley.

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Osprey. (Greg Seitz/St. Croix 360)

Astronomy

On Saturday the 18th look for the planet Venus to the left of the crescent Moon in the west after sunset. On Tuesday the 22nd get up early and look in the south before dawn for the Lyrid Meteor Shower. In the evening look for the planet Jupiter below the waxing Moon. A moon is called “waxing” when the part we see gets larger each night as it gets closer and closer to being full.

Birds

Many of the migratory birds that will nest at Afton have returned from the south. On the prairie look for Meadowlarks, Eastern Bluebirds, Tree Swallows, and Bobolinks. Meadowlarks wintered in the southern part of the United States, Eastern Bluebirds in the U.S. or Mexico, Tree Swallows in Florida and Central America, and Bobolinks went all the way to South America. Tree Swallows often nest in bluebird boxes. One of the reasons the bluebird boxes at Afton are set out in pairs is that the tree swallows that occupy one box will not tolerate another pair of tree swallows nesting in the second nearby box. But they don’t mind if bluebirds nest there!

Down by the river look for Great Blue Herons and Great Egrets along the banks and Loons and Mergansers passing through on their way north. A few Loons and Mergansers may spend the summer on lakes in our area, but most go farther north.

The first warblers begin to arrive about now. Yellow-rumped warblers are one of the more common species. You might also see Yellow Warblers, American Redstarts, and Prothonotary Warblers.

At this time last year visitors to Afton saw Bluebirds, Osprey, Meadowlarks, Song Sparrows, Field Sparrows, Tree Sparrows, Northern Flickers, Chipping Sparrows, and heard a Ring- necked Pheasant.

Amphibians and Reptiles

Look for both Painted and Snapping Turtles basking on sunny days. Both species live at Afton. The warmth of the sun helps them to digest what they’ve eaten. And go out after sunset to listen to the raucous calling of frogs.

Insects

There are two species of “lady” butterflies at Afton in the summer – the Painted Lady and the American Lady. It is too cold for the ladies to over-winter in Minnesota, so like the Monarchs they go south for the winter. Also like the Monarchs, it takes more than one generation to make the return trip north to Minnesota. The Painted Ladies don’t go far south and as a result return sooner than the Monarchs, arriving in late April. We usually don’t see American Ladies until later in the year – they have an established population in the southern United States and successive broods make their way farther and farther north over the course of the summer. The two species are very similar in appearance. If you see them when they’re perched, the American Lady has two big eyespots on its hind wing, while the Painted Lady has four smaller eyespots. The Painted Lady is the most widespread butterfly in the whole world – it lives on all continents except Australia and Antarctica.

Red Admirals are another butterfly that migrates, and like the Painted Lady may return to Afton as early as late April. Red Admirals overwinter either as adults or in the pupal stage, when the larva has transformed itself into a chrysalis but not yet metamorphosed into a butterfly. Overwintering adult Red Admirals do not survive very cold temperatures, so the ones we see here in early spring have probably flown in from farther south. You might also see Mourning Cloaks and Eastern Commas, which overwinter at Afton as adults and are on the wing as soon as we start having warm sunny days; at this time last year a visitor reported seeing an Eastern Comma.

While the Painted Ladies usually arrive before the Monarchs, on April 20 of 2025 a visitor to Afton reported seeing a Monarch!

Plants and Fungi

Some of the spring ephemerals blooming in April are Wood Anemone, Yellow Trout Lily, Bishop’s Cap, and Wild Violets. Wild Violets have an unusual strategy for dispersing their seeds called “Ballistic Dispersal”. Their seeds form inside a capsule that explodes when the capsule dries and compresses the seeds. The seeds are covered with a sweet substance that is attractive to ants. Ants gather the seeds and take them underground, but the ants just eat the sweet stuff on the outside of the seed, and not the seed itself, in effect planting the seeds in a new location!

And while you’re looking for spring ephemerals in the woods, keep a lookout for the bright red of the scarlet cup fungus. The “cup” is the fruiting body of an organism that is more like animal than a plant, and the organism sends up its fruiting bodies from underground at about the same time the spring ephemerals bloom. You’re most likely to find Scarlet Cups in the leaf litter around the base of oak and basswood trees.

Along the edges of the woods look for Kittentoes and Little-leaf Buttercups, and on the prairie look for Prairie Smoke. Kittentoes are a member of the genus Antennaria, which takes its name from stamens that project out away from the flower like the antennae of insects. The Antennaria are a favorite host plant of the both the Painted Lady and the American Lady butterfly, so if you see a caterpillar on Kittentoes it may become a Lady butterfly someday.

Weather observations

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

Friday, April 172025: red sky in the morning, thunderstorm in the evening; 2024: cloudy and breezy, 50s; 2023: Sunny, 50s; 2019: rain with thunder and lightning; 2016: high in 70s
Saturday, April 182025: ¼” rain; 2024: blustery with temperature in the 40s; 2021: flurried and rain in the morning, in the 20s; 2020: sunny and mild, in the 50s; 2013: record snowfall of 6.4”; 2004: record rainfall of 1.04”
Sunday, April 192023: Thunderstorm in the evening; 2020: partly sunny with a cold wind, temperature in the 50s; 2013: 6” heavy wet snow overnight
Monday, April 202025: rain from late afternoon into evening; 2023: rain throughout the day, temperature in the 40s; 2022: rain the afternoon, temperature in the 40s; 2019: sunny and in the low 70s; 2013: record low of 21°
Tuesday, April 212025: ¾” rain overnight; 2022: Sunny day in the 50s; 2016: ¼” rain overnight, in the 50s; 2002: Record snowfall of 6.6”
Wednesday, April 222025: clouds and sprinkles early, then sunny and 60s; 2020: pleasant day in the 60s; 2001: record rainfall of 2.21 inches
Thursday, April 232025: cloudy and mild, high over 70°; 2022: Temperature in the 60s, with thunderstorms in the morning and evening; 2016: clear and temperature in the 40s in the morning, with dew on the grass

Photo credits:

All photos and images used by permission.

Copyright Nina Manzi, except:

  • Keith Henjum: Hooded Mergansers
  • Sherri Holliday-Skar: Great Blue Heron
  • Dean Lokken: Great Egret, Meadowlark
  • Paul Ludden: Bobolink
  • Jamie Olson Kinne: Eastern Comma
  • Gary Sater: American Redstart, Common Loon, Eastern Bluebird, Osprey, Pheasant, Red-breasted mergansers, Ring-necked Pheasant, Song Sparrow, Yellow Warbler, Yellow-rumped Warbler
  • Greg Seitz, for St. Croix 360: Prothonotary Warbler

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