Afton State Park phenology update: Winter wildlife from owls to snow fleas

Life continues even during a deep freeze.




6 minute read

Juvenile great-horned owl, Sunrise River watershed. (Andy Birkey/iNaturalist)

Note: Nina Manzi is a long-time volunteer at Afton State Park who has long recorded and shared seasonal observations at the visitor’s center. Due to COVID closures, St. Croix 360 is publishing her updates when possible. Thank you, Nina!


Venus is visible in the morning sky through mid-month – say goodbye to it for a
while as it will move behind the sun until it reappears as an evening star in May. On Thursday
the 18th look for Mars above the waxing moon in the evening.


Great horned owls have been hooting to establish territories and pair bonds, and nest in
late winter. Here’s a description of their nesting habits courtesy of Nathan Pasch (illustration)
and Carolyn Bernhardt (text), both with the University of Minnesota’s College of Veterinary
Science, with an expert insight from Lori Arent, assistant director at The Raptor Center.

Great horned owls, opportunistic nesters.

  • Average nest size: This varies based on what animal built the nest.
  • Location: Great horned owls usually take over nests built by other animals, so their location varies. But great horned owls can also nest in cavities in live trees. They may also nest in some unexpected places, such as dead snags, deserted buildings, cliff ledges, and human-made platforms.
  • Materials: Adopted nests are usually made by red-tailed hawks, crows, or squirrels and made out of sticks and vegetation.
  • Strategy: Great horned owls do not work to maintain the nest they adopt, so by the time their clutch of eggs hatch, it may be a little worse for wear due to harsh winter weather. They rarely reuse a nest in subsequent mating seasons. In some areas, they may line the nest with shreds of bark, leaves, downy feathers plucked from their own breast, fur or feathers from prey, or trampled pellets. In others, they may not line the nest at all.
  • Clutch size range: 1-4 eggs
  • Timing: 30-37 days of egg incubation, followed by nestlings in the nest for up for 42 days.

From the expert: “At TRC, we often see young great horned owls in the clinic, both because great horned owls are the most common large owl found in the Twin Cities area, and because their young frequently fall from their haphazard nests after hatching in the spring.” Arent says. “There is estimated to be roughly one great horned owl nest every two miles in the Twin Cities.”


Have you seen two or more squirrels running through the woods, one after the other? Squirrels chase each other throughout the year to defend a territory, and young squirrels chase around in play that serves as practice for more serious adult chasing.

In late winter what you see may be a mating chase, in which several males follow a female either slowly or quickly in hopes of mating. Gray squirrels give birth 40 to 44 days after mating, in a big nest made out of leaves.

Newborn squirrels are blind and have no fur. They remain in their leafy nest, cared for by their mother, for seven to ten weeks after birth. Look for them to be out and about while learning from Mom how to be a squirrel in late March and April.


Spruces are another variety of conifer you may see at Afton. The Norway spruce is a non-native, but they are at Afton anyway and their cones are an important source of seeds for
red squirrels and other animals.

All spruces have single needles that attach directly to the twig on a short woody “peg”. The needles are stiff in bristly. If you touch a spruce it will feel like pin-pricks. The needles of the Norway Spruce are one-half to one inch long, and have a pleasant smell when crushed.

All spruces also have flaky bark in scales. Norway spruce’s bark is reddish-gray in color.

Spruces have cones that are papery and less substantial than pine cones. On the ground around spruces trees you may see twigs and the central core of spruces. Red squirrels were here! They chew through spruce twigs so that the cones drop to the ground, then they demolish the cones to get to the papery seeds. The cone of the Norway spruce is two to seven inches long, and if you see one in a tree it will be hanging down from its branch.

Insects and arthropods

Bees and fleas! In winter? On mild days in winter bees may leave their hive or overwintering location (for solitary bees that don’t live in hives) and take what is called a “cleansing flight”. Bees are notorious for keeping their hives and nests clean, and warm and sunny winter day gives them a chance to fly outside and . . . poop!

And on those same mild days you might see what look like flecks of black pepper hopping around on the melting snow. It’s not pepper, but it’s an animal called the “snow flea”. Snow fleas aren’t really fleas, and they aren’t even insects. They’re arthropods, a group that includes spiders and crustaceans. They are a type of springtail, and live in the leaf litter of the forest floor. Their diet consists of decaying organic material in the soil. They produce a snow flea-antifreeze that allows them to stay active all winter, and when the snow cover grows thin you may seem them jumping around, curling their tails under them and the “springing” from one place to another. I’m hoping to get a photo of them one day.

Weather observations

Here are some weather observations for this time period from past years

Friday, February 52005: Record high of 51°
Saturday, February 6In non-COVID years, the Afton State Park candlelight event would have taken place on this Saturday. Hope this can happen in 2022 and look forward to seeing you then!
Sunday, February 72019: Record snowfall of 5.9”
Monday, February 82019: 10° below zero to start the day
Tuesday, February 92014: Sunny and calm, temperature near zero
Wednesday, February 102019: Single digits, four to five inches of new snow
Thursday, February 112017: Temperature in the 40s
Friday, February 122019: Record snowfall of 5.5”
Saturday, February 132019: Clouds, high in the 20s.
Sunday, February 142017: High in the 40s.
Monday, February 152019: Near zero in the morning, rising into teens on a sunny afternoon
Tuesday, February 162016: Fog in the morning, clearing by afternoon. High in mid-30s
Wednesday, February 172017: Record high of 63°; 2014: record snowfall of 4.9”
Thursday, February 182019: Cold and calm and near 10° in the morning.

Photo credits

All photos copyright Nina Manzi, except:

  • Stephen B. Antus Jr., MN Conservation Volunteer: Deer with one antler
  • Carolyn Bernhardt, University of MN College of Veterinary Medicine: great horned owl nestingtext
  • Michael Furtman, MN Conservation Volunteer: Chickadee
  • Keith Henjum: Hairy Woodpecker
  • Bill Johnson, MN Conservation Volunteer: Plasterer bee, Sweat bee
  • Bill Marchel, MN Conservation Volunteer: Buck deer, deer shed, gray squirrel
  • Nathan Pasch, University of MN College of Veterinary Medicine: great horned owl nest illustration
  • Gary Sater: Cardinal, juvenile great-horned owl
  • Richard Hamilton Smith, MN Conservation Volunteer: Red pine
  • Tammy Wolfe, MN Conservation Volunteer: Great-horned owl and nestling.


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Afton State Park phenology update: Winter wildlife from owls to snow fleas