Afton State Park phenology, March 8 to 14

Many birds follow open water back to the St. Croix Valley, while woodpeckers work on nests.

March 8, 2024

4 minute read

Red-bellied woodpecker, Afton State Park (lanetheadventurer/iNaturalist)

Astronomy

All through the month of March the planet Venus is a brilliant morning star low in the southeastern sky before sunrise. Daylight Saving Time begins at 2:00 AM on Saturday, March 10. Turn your clocks ahead one hour! Starting on the 11th, we will have more daylight in the evening, and less in the morning, but the total length of daylight each day will continue to grow longer and longer as we approach the Spring Equinox.

Birds

Many species of birds follow open water north in the springtime, including mergansers, herons, egrets, bald eagles, and our state bird, the common loon. Look for all of these at Afton as the ice goes out on the St. Croix. Some may stay for the summer, while many will travel farther north.

Ever wonder how birds can handle having their feet in icy-cold water? For one thing, their feet consist mostly of bones and tendons with very little muscle tissue, so there isn’t much there to get cold. And then they do this thing called “countercurrent heat exchange”. As warm blood travels from a waterbird’s heart down toward its feet, the artery runs directly alongside the vein carrying cold blood back up to the heart. The heat transfers from the warm blood in the artery to the cold blood in the vein before it even reaches the feet! The cold blood is still able to carry oxygen into the feet. Very little heat escapes from the foot into the water, and the warmed up blood in the veins means that the bird does not have to use extra energy to re-heat the venous blood as it returns to the heart.

Before the trees leaf out is a good time to listen and look for woodpeckers. There are at least four species at Afton. From smallest to largest: downy woodpeckers, hairy woodpeckers, red-bellied woodpeckers, and pileated woodpeckers. There may also be red-headed woodpeckers, but they are in serious decline across their historic range. They are the only woodpecker in Minnesota that hunts primarily by flycatching, and many have been killed by passing cars when they leave a perch near a road to dart out to catch an insect. Their preferred habitat is the oak savanna, which is one of the ecosystems at Afton. If you see one, let us know! Starting in mid-February all woodpeckers begin looking for dead trees in which to hollow out nesting cavities. You may see one at work when you hike at Afton.

Mammals

Many species of mammals call Afton home. You might visit the park many times without seeing some of them, like badgers and fishers. Among the mammals you are most likely to see when visiting the park are chipmunks, red squirrels, rabbits, and white-tailed deer. Chipmunks come out of their burrows around this time of year. They are not true hibernators and wake up every few days in winter to eat, but in the fall they stash a large supply of seeds in their burrows so they don’t have to go out to search for food.

Insects

The Monarch butterflies who flew south from Minnesota to the oyamel pine forests of Mexico last fall have begun the return journey. These individuals won’t make it all the way to Minnesota. They will pause along the way to mate and lay eggs, and it will be their grandchildren or great-grandchildren who fly into Afton in May and June. While we’re awaiting their arrival, keep a lookout for mourning cloaks, Milbert’s tortoiseshells, and eastern commas, three species of butterflies that overwinter in Minnesota as adults, which means they are usually the first butterflies we see on sunny March days.

Trees

The Norway Spruce is not native to Minnesota, but there are plenty of them at Afton. Here’s an interesting thing about spruces: the cones will open and close in response to changes in humidity. The scales on a cone are called “bracts”, and certain cells in the bracts change orientation when the humidity decreases, causing the bracts to open. This allows the seeds to drop out of the cone. What’s really amazing is that this happens even when the cones have fallen off the tree! If there is a spruce tree in your neighborhood, try bringing a cone with closed bracts inside and see what happens.

Weather observations

Here are some weather observations from the Afton State Park area from past years.

Friday, March 8	2020: sunny and in the 60s; 2016: record high of 70°; 1999: recordnowfall of 12.5”
Saturday, March 9	2023: light snow and rain throughout day; 2021: record high of62°; 2014: breezy and in the low 40s; 2003: record low ofminus 10°;
Sunday, March 10	2023: 2” wet snow overnight; 2021: record rainfall of 0.69”; 2012 and 2015: record high of 66°; 2009: foggy and misty through day; 2001: St. Croix River frozen over
Monday, March 11	2023: snow off and on through day, maybe 3” in all; 2012 and 2016: tied for record high of 66°; 2013: dusting of snow overnight; 2002: St. Croix River frozen over
Tuesday, March 12	2023: 4” snow overnight; 2020: Drizzly day in high 30s; 2016: record high of 70°; 2000: open water on St. Croix River
Wednesday, March 13	2017: two inches of snow overnight, in the teens; 2012: record high of 67°; 2006: record snowfall of 9.9”
Thursday, March 14	2018: sunny and in the 20s in the morning; 2012: record high of 73°