Afton State Park phenology September 8 to 14

Birds are beginning to move south, as summer’s last wildflowers bloom.




3 minute read

St. Croix River viewed from Afton State Park. (Greg Seitz/St. Croix 360)


Have you been rising early to see the planet Venus in the eastern sky? Each day it’s a little higher, and will reach its highest point above the horizon around the middle of September. On Monday the 11th look for it near the crescent Moon. And you might catch a glimpse of tiny Mercury, also. It will be below Venus, closer to the horizon.


Mallard ducks and Canada geese are noisy as they form flocks and take practice flights in anticipation of migration. They will fly far enough south to find open water and feeding grounds, and continue south as necessary, generally ending up in the southern U.S. or Mexico. Many warblers are already quietly heading south. They are sometimes called “neotropical migrants” meaning they migrate to the tropics of the new world: the Caribbean, Central America, and northern South America. You might see yellow warblers, American redstarts, and yellow-rumped warblers passing through Afton.


Rabbits, squirrels, raccoons and bats are some of the mammals you might see at Afton. Rabbits and squirrels are active all year. Raccoons are semi-hibernators; they retreat to their dens on cold days but venture out when the weather is mild. Bats are true hibernators. They spend the winter in big groups in a cave or sheltered area called a hibernaculum. The white nose fungus disease afflicting bats spreads easily in the close quarters of the hibernaculum, causing the bats to wake up in the winter. The energy loss associated with waking up before spring often results in death. Please help protect our local bats by staying out of caves; you may unknowingly carry the fungus inside on your shoes or clothing.

Amphibians and reptiles:

Frogs and toads have for the most part stopped calling in the evenings, but you may still see them out and about hunting for insects.


Butterflies have a variety of strategies to deal with winter. Monarch butterflies make a long epic migration all the way to Mexico, roosting in large groups on trees in the evenings as they travel. Painted Lady butterflies also migrate also, but unlike monarchs they don’t go to the same wintering place every year, and don’t go nearly as far. And when the time comes Mourning Cloak and Eastern Comma butterflies will burrow into leaf litter or creep under tree bark and overwinter as adults. Swallowtail butterflies overwinter in the chrysalis form; the caterpillar makes a cocoon, then waits patiently until warm weather in spring to complete its metamorphosis into a butterfly.

Dragonflies are about the most amazing fliers on the planet. Take a few minutes this week to watch one changing direction in mid-flight as it hunts. All dragonflies are predators, and will eat anything they can catch, most often midges and mosquitoes. There are many families of dragonflies, and each contains many species. Members of the Skimmer family include the meadowhawks, whitefaces, gliders, and pennants; they all tend to “skim” through the air. Some skimmers that are still on the wing in mid-September are the White-faced Meadowhawk, Autumn Meadowhawk, Variegated Whiteface, Dot-Tailed Whiteface, Wandering Glider, and Hallowe’en Pennant.


The last wildflowers of the season to bloom are blooming now: Sky-blue Asters, Canada Goldenrod, and White Snakeroot. And where you saw Wild Roses earlier this year, look for their fruit, called rose hips, which many animals like to eat.

Weather observations

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

Friday, September 82020: Cool day starting in the 40s, rising to a high in the 50s; 2010: high 40s overnight
Saturday, September 92020: high temperature of only 50° with light rain; the earliest the high has been this low ever! 2000: record rainfall of 1.79 inches
Sunday, September 102020: sunny and pleasant, in the 60s
Monday, September 112016: a breezy day with high temperature near 80°
Tuesday, September 122015: 50s in the morning, with a high near 70°
Wednesday, September 132021: clouds through the day, temperature in the 70s; 2014: overnight low in the 30s, warming into the 60s
Thursday, September 142016: high 40s in the morning, rising into the 60s

Photo/Image credits:

All photos copyright Nina Manzi, except:

  • Keith Henjum: Raccoon, Yellow-rumped warbler
  • Jamie Olson Kinne: Eastern Comma butterfly
  • Dean Lokken: Mallard duck, Northern leopard frog, Rabbit
  • Deborah Rose, MN Conservation Volunteer: Bat
  • Gary Sater: American redstart, Yellow warbler


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Afton State Park phenology September 8 to 14