Afton State Park phenology, week of April 16

Frogs are calling and monarchs are making the way back north.




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View from Afton State Park. (Brett Whaley/Flickr)

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!


Mars will be above the crescent moon in the evening on the 16th, and below the  moon on the 17th. Get up before sunrise on Thursday the 22nd and watch the southern sky for  the Lyrid meteor shower. 


White-throated sparrows are passing through our area heading north. Some people say  their whistling call sounds like “O Sweet Canada Canada”, others think it sounds like “Old Sam  Peabody Peabody”. Song sparrows have returned and some will stay here the whole summer.  American robins are starting to build nests. This time of year, before the trees leaf out, is a  good time to look for last year’s nests. 

And don’t forget to look UP for birds. Flocks of pelicans overhead are easy to identify – they are  very large white birds with black on their wings. Turkey vultures have returned to our part of  Minnesota. Look for them circling. Their wing feathers are light darker toward the leading edge  of the wing and lighter at the back. They hold their wings in a “V” shape as they glide and they wobble a lot (in contrast to eagle and hawks, which hold their wings straight out and glide  smoothly. Sandhill cranes pass by high overhead. They hold their necks out ahead of them as  they fly, with their legs trailing out behind them. This distinguishes them from herons, which fly  with their necks curled back toward their bodies.

Amphibians and Reptiles

By mid-April there are FOUR species of frogs calling in the evening  hours: Spring Peepers, with their high-pitched peeping, Chorus Frogs, with their trilling call that  sounds like running your finger along a comb, the chuckling call of the Wood Frogs, and now  the low snoring call that ends in a croak or cluck of the Northern Leopard Frogs. 


The Monarchs are on the way! All overwintering butterflies have departed the oyamel pine forests of Mexico. These individuals won’t be the ones to return to Minnesota – the  butterflies that spent the winter in Mexico have mated and laid eggs in Texas or Oklahoma, and  first reports are coming in that those eggs have hatched and Monarch larva are busy eating  milkweed plants. This new generation of Monarchs will make another stop to mate and lay  eggs, and those eggs will lead to the generation of butterflies that will return to Minnesota in  May or June. Here in Minnesota in mid-April the seed pods of last year’s milkweed plants have  opened, and the seeds are blowing in the wind, dispersing over the landscape. Some of them  will land in hospitable places and grow into milkweed plants, just in time for the return of the  Monarchs. 

While we’re waiting for the Monarchs to return, keep a lookout for Spring Azures. Spring Azures  overwinter as pupae. Last fall their larva finished eating and made their cocoons, where they  rested until the spring sunshine and longer days signaled that it was time to complete  metamorphosis and emerge as butterflies. As the name suggests, Spring Azures are a vibrant  blue on the top side of their wings. But they are rather pale on the underside of their wings,  and when they land they almost always hold their wings closed. Sometimes people are  reluctant to believe that the pale colored butterflies they see perched are the blue butterflies  they just saw on the wing. 


Spring flower season continues! Hepatica, bloodroot, Dutchman’s breeches, yellow trout lily, large-flowered bellwort, wild ginger, and wild violets are still in bloom, and joining them about mid-month are Jack-in-the-pulpits and spring beauties. They’re called  “ephemerals” for a reason – they won’t be around long! So take the opportunity to hike  through the woods and enjoy these early flowers soon.  

Weather observations 

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

Friday, April 162003: record rainfall of 1.04 inches
Saturday, April 172019: rain through day with thunder
Sunday, April 182013: record snowfall of 6.4 inches
Monday, April 192020: partly sunny in the 50s with a cold wind
Tuesday, April 202013: record low of 21°; 2019 sunny and pleasant in the low 70s
Wednesday, April 212002: record snowfall of 6.6 inches
Thursday, April 222001: record rainfall of 2.21 inches; 2020: pleasant, temperature in the 60s

Photo credits

All photos copyright Nina Manzi, except: 

  • Dean Lokken: American Robin, Northern Leopard Frog, Turkey Vulture
  • Gary Sater: Song Sparrow, Sandhill Cranes 
  • Allen Blake Sheldon, MN Conservation Volunteer: Boreal Chorus Frog, Spring Peeper 


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Afton State Park phenology, week of April 16