Afton State Park phenology, September 15 to 21

Birds starting south, whitetail bucks have antlers, and the last dragonflies are on the wing.




3 minute read

Afton State Park Visitor Center (Greg Seitz/St. Croix 360)


On Thursday the 21st get up early and look for Mercury just below Venus. This is one of the best opportunities this year to see Mercury.


American Goldfinches feed on the seed heads of coneflowers and bee balm plants. This is a good time of year to look for Green Herons and Black-Crowned Night Herons along the edges of waterways. And Pelicans are moving through, migrating south. When they are in flight you can recognize them by their white bodies and the black on the leading edges of their wings and on what are called their “primary” feathers, which are the ones at the ends of their wings. The pigment melanin in the black feathers makes those feathers stronger and more resistant to abrasion. White Pelicans have the second biggest wingspan of any bird in North America, behind the California Condor. The pelicans passing through our area will probably spend the winter along the coast of the Gulf of Mexico.


Deer have almost fully changed to their winter gray coats, as you can see on the individual in the first photo. Deer, like cows, are ruminants. After they eat they regurgitate their food and chew it again to make it easier to digest. The deer in the first photo is probably ruminating. Buck deer have grown antlers and rubbed the velvet off of them; antler growth in deer and related species is one of the few examples of regeneration among mammals. Gray Squirrels continue to gather acorns and black walnuts and to store them for the coming winter.

Amphibians and reptiles

You may still see frogs and toads out and about, but they are not the only amphibians at Afton. On cool fall mornings after it rains, watch for tiger salamanders moving south of the park to spend the winter in abandoned tunnels and burrows below the frostline. If you see them on 70th street, try not to run them over! That’s where this photo was taken.


Look for Monarch butterflies passing through, going south. The Monarchs that emerged from their chrysalises in August were in “reproductive diapause”, which means that they weren’t fully developed and won’t be able to mate and lay eggs until next spring when they are on their way north from their overwintering sites in Mexico. This adaptation allows them to conserve energy for their long journey south. How did they know to emerge in reproductive diapause? Scientists think that the developing butterfly inside the pupa is aware of the length of day, and the age of the milkweed plant to which the pupa is attached. The butterflies that emerge in August will travel thousands of miles to Mexico and spend the winter in large colonies clustered on oyamel fir trees. After they leave Mexico to head north these individuals will develop the ability to mate and lay eggs, and it will be their grandchildren or great-grandchildren who will arrive back in Minnesota next spring.

Some of the dragonflies still on the wing in late September are the Lake Darner, and the Twelve- spotted Skimmer. The Twelve-spotted Skimmer takes its name from the number of black spots on its wings. The males also have white spots, while the females do not.


Sky-blue Asters and Canada Goldenrod continue to bloom. Milkweed and Butterflyweed seed pods are just starting to open. Both have fluffy seeds that drift in the wind.

Weather observations

Friday, September 152022: Hazy sunshine in the 80s. Record low of 36° in 1964, 2007, and 2011
Saturday, September 162021: 60s early, rising into the 80s; 2013: temperature in the 60s with an inch of rain
Sunday, September 172021: morning thunderstorm with many downed trees; 2015: Record rainfall of 2.37”;
Monday, September 182022: clouds till late afternoon, high in the mid-60s; 2016: sunny and high near 80°
Tuesday, September 192019: sunny, in the low 80s; 2011: foggy morning, with clearing skies and high in the low 70s
Wednesday, September 202022: hot and humid, record high of 92°; 2018: record rainfall of 3.28”
Thursday, September 212019: quarter inch of rain, high in low 70s

Photo/Image credits

All photos copyright Nina Manzi, except:

  • Bill Marchel: MN Conservation Volunteer: Buck Deer
  • Gary Sater: American Goldfinch, Green Heron, Whitetail Deer


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Afton State Park phenology, September 15 to 21