Afton State Park Phenology, November 27 to December 10, 2020

There’s still lots to see, even as winter settles in along the St. Croix Valley.




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Afton State Park, December 2017 (Photo by Tony Webster via Wikimedia)


Monday, November 30th brings the Full Beaver Moon; it’s not clear if this moon takes its name from a high degree of beaver dam-building going on at this time of year, or from it being a good time to trap beavers to ensure a good supply of warm pelts for the winter.


Many birds who are at Afton for the summer have gone farther south for the winter. But other birds who go farther north for the summer have come south to Afton for the winter! When you hike at the park look for flocks of dark-eyed juncos, golden-crowned kinglets, red-breasted nuthatches, and tree sparrows. The red-breasted nuthatches don’t come south every year, only in years when their preferred winter food, the seeds of conifers, are in short supply farther north. Many conifers produce large numbers of cones one year and very few the next, which leads to a two-year cycle in which the red-breasted nuthatches come south to Afton (and other places) in one year but not so much in the next.


Most people don’t think twice about deer growing new antlers each fall then losing them in the winter. But this re-growth of antlers by members of the deer family is the one and only instance of organ regeneration among mammals. This is a prime time to see bucks with full racks of antlers; after the first of the year you may come across dropped antlers or “sheds” out in the woods. Deer tracks are among the easiest tracks at Afton to identify – keep a lookout for them when you’re hiking.

Reptiles and amphibians

What do frogs and toads do in the winter? American toads are good diggers and burrow down below the frost line and sleep away the winter in a state of torpor, sometimes waking up enough to move up and down in order to stay just a bit below the frost line. If you were planting bulbs this fall you might have surprised a toad or two!

Frogs that spend most of their time on land, called “terrestrial frogs”, like the wood frog, are not good diggers and look for cracks and spaces in rocks and logs. Aquatic frogs, like the leopard frog, don’t dig into the mud at the bottom of a pond but lie on top of the mud or only partially buried so they can continue to breathe. Frogs, unlike toads, actually freeze but have high levels of glucose in their vital organs which acts as an antifreeze and prevents ice from puncturing their cells. For a time their hearts actually stop! But they thaw out in the spring and come back to life. Pretty amazing!


If you take a walk in the woods you might notice some deciduous trees that are still holding their leaves. They are probably oaks! The scientific term for retaining dead leaves that are normally dropped is “marcescence”. The leaves eventually drop before the new leaves open up in the spring. For the nature-lover, marcescence in oaks means that you can still learn to distinguish oak trees from one another in the winter. Here are photos of the bark, leaves, and acorns of two oaks that are present at Afton, the Swamp White Oak and the Northern Red Oak.

White oaks have rounded lobes. The Swamp White Oak grows in moist soils along rivers and wetlands, and can live to be 150 to 200 years old! A knobby cap covers the top half of its acorn. The leaves are four to seven inches long, and are widest above the middle.

Red and black oaks have pointed lobes. The Northern Red Oak has only shallow indentations or “sinuses” between the lobes on its leaves, and the cap only covers the very top of its acorns.

Weather observations

Friday, November 27

high of 10°
Saturday, November 282015:30s and sunny
Sunday, November 292009:light snow overnight
Monday, November 302016:high 30s with light rain
Tuesday, December 12012:fog and low clouds through day
Wednesday, December 22013:alternating rain and snow through day
Thursday, December 32012:high in the 50s
Friday, December 42017:record high of 57°
Saturday, December 52001:record high of 63°
Sunday, December 62013:cold and clear, high in single digits
Monday, December 72015:high of 46°
Tuesday, December 82010:single digit overnight with fog rising off open water
Wednesday, December 92012:record snowfall of 10.5”
Thursday, December 102013record snowfall of 1.8”

Photo credits:

All photos copyright Nina Manzi, except: Bill Marchel, Minnesota Conservation Volunteer: first deer track and both buck deer photos