Afton State Park phenology, August 30 to September 5

Grey-headed coneflower, Afton State Park. (Greg Seitz/St. Croix 360)

Birds

Some American robins have begun to form flocks and slowly move south. Others will stay in this area all winter. Robins that go south travel just far enough to find enough insects to eat to sustain themselves. Robins that stay in this area switch from eating insects to eating fruit. Look for groups of turkey vultures soaring overhead; they may have started on their way south also.

Mammals

Gray squirrels are busy gathering black walnut seed pods, fruit, and acorns. Whitetail deer are growing in their gray winter coats, which will replace the summer red. And raccoons are on the prowl at dawn and dusk. Their closest relative other than the ringtails of the southwest is . . . the bear!

Amphibians and reptiles

Snapping and painted turtle eggs are hatching and young turtles moving from nests to the water. Whether the baby turtles are males are females depends on the temperature during the middle one-third of the time when the eggs were incubating. If it’s cool, below 82° F, all the turtles will be males. But if it’s hot, above 88° F, all the turtles will be female. In between those two temperatures and some will be males and some will be females. All young turtles are vulnerable to predators when they are making the journey from their nest to the water. And turtles of all ages and also snakes bask in the September sunshine.

Insects

Monarch Butterflies have begun their southward migration, and the ones that survive all the hazards along the way will fly about 2,500 miles to the Oyamel Pine forests of Mexico. On cool mornings look for groups of them clustered together on trees where they roosted overnight, and in the daytime watch for individual butterflies flying south. Their average speed is 11 miles per hour. If they fly for 12 hours a day that means it takes them almost three weeks on the wing to reach the Oyamel Pines. Green Darner Dragonflies migrate, also. In the late afternoon and evening look up to see them circling and slowly moving south.

There are over 350,000 species of beetles that have been identified, with more being found almost every day! You can tell beetles apart from other insects because the front pair of wings is hardened into what is called a “wing-case” protecting the second pair of wings, which the beetle uses for flying. One beetle common at Afton is the Goldenrod Soldier Beetle. As you can see in the photos, they visit many kinds of plants, not just goldenrod! There are approximately 3,500 species of soldier beetles in the world. The weevils are another group of beetles, and there are more than 60,000 species of them! One kind you might see at Afton is the pale green weevil, which is indeed pale green in color.

Plants

Wildflower season is winding down; in early September look for vervain, goldenrod, and yarrow on the prairie. Yarrow has very lacy and feathery leaves. And sumac leaves are starting to turn red, signaling the coming of autumn.

Lichens

Ever wonder just what a lichen is? There’s no simple answer, though many people have tried. One way to explain a lichen is based on its parts. Lichens always include a fungus along with either an alga or a cyanobacteria. Some lichens include multiple fungi, algae, and cyanobacteria. Lichens are mini- ecosystems living together in a symbiosis. “Symbiosis” means “live together”, and each member of the group benefits from the others. In the case of lichens, the alga generates energy through photosynthesis. And the fungus provides a structure and can shield the alga from burning up from too much sunlight.

Lichenologists classify lichens into three groups: Crustose, Foliose, and Fruticose. Lichens in each of those groups can live on rocks, trees, or on the soil. Lichenologists call the surface the lichen lives on the “substrate”.

Crustose lichens are the ones most people are familiar with. They are very flat, and often have rock as their substrate. Common Goldspeck is a crustose lichen.

Foliose lichens are mostly flat but have curly edges, and if you look you can see both the top and the underside of the lichen. Common Greenshield is a foliose lichen that lives on trees.

Fruticose lichens are bushy or shrubby. One that you may see at Afton is the Boreal Oakmoss, which isn’t a moss at all but is a fruticose lichen that lives on trees. The Oakmoss lichens are more tolerant of air pollution than other lichens so they are more likely to live near urban areas. If you want to take a field trip to see lots of lichens, visit northeastern Minnesota, which is home to one of the most diverse arrays of lichens in all of North America!

Weather observations

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

Friday, August 30	2023: 70s, clouds, with haze from Canadian wildfires; 2022: high near 80°; 2020: 70s, sunny and pleasant
Saturday, August 31	2020: thunderstorm before sunrise with ½” of rain
Sunday, September 1	2023: hot and hazy, in the 80s; 2015: hazy and muggy with a high in the 80s
Monday, September 2	2015: low 80s and overcast; 2000: record rainfall of 1.97”
Tuesday, September 3	2023: hot and dry, upper 90s; 2021: rain overnight and through afternoon, 1” in total; 2012: high in the low 80s
Wednesday, September 4	2015: muggy and 70° in the morning; 2013: muggy and near 90°
Thursday, September 5	2023: upper 90s, breezy; 2015: hazy, hot and muggy, near 90; 2014: high in mid-60s