Afton State Park phenology week of September 4, 2020

Migration begins for birds and butterflies, while animals that will stay the winter begin their preparations.




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Afton State Park Visitor Center (Photo by McGhiever via Wikipedia)

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.


Mars and the Moon. (Photo by cafuego via Flickr)

Look for Mars near the just past full moon on Saturday, September 5th. Venus is bright in the pre-dawn sky in the east.


Some American robins have begun to form flocks and slowly move south. Others will stay in this area all winter. Look for groups of turkey vultures soaring overhead; they may have started on their way south also. And you may see hooded mergansers on the river.


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 is 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. Young turtles are vulnerable to predators at this time. And turtles of all ages and snakes bask in the September sunshine.


Monarchs butterflies have begun their southward migration. On cool mornings look for groups of them clustered together on trees where they roosted overnight. Green darner dragonflies migrate, also. In the late afternoon and evening look up to see them circling and slowly moving south.

“True bugs” are a group of insects that all have sucking mouthparts. Unlike many other insects, true bugs and also grasshoppers undergo only an incomplete metamorphosis and do not have a larval form. Instead a “nymph” which is a miniature version of the adult hatches directly from an egg. As the insect grows, it molts its exoskeleton and a new soft one underneath hardens. These in-between forms are called “instars”. The leaf-footed bug, twice- stabbed stinkbug, and sharpshooter leafhopper are some of the true bugs you might find at Afton. Bother the stinkbug at your own risk – when disturbed it emits a liquid that really does stink!


Wildflower season is winding down; in early September look for vervains and goldenrods on the prairie, and you may still see some jewelweed in wet areas. And sumacs are starting to turn read, signaling the coming of autumn.

Weather observations

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

Friday, September 42013: muggy and near 90°
Saturday, September 52014: high in mid-60s
Sunday, September 62015: thunderstorm, 5/8” rain
Monday, September 72016: humid with a high in the upper 70s
Tuesday, September 82010: high 40s overnight
Wednesday, September 92000: record rainfall of 1.79”
Thursday, September 102015: temperature in 60s with light rain

Photo credits: All photos copyright Nina Manzi, except: Keith Henjum, Hooded mergansers, Raccoon; Dean Lokken, American Robin, Turkey Vulture


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Afton State Park phenology week of September 4, 2020