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Phenology Report: Who hooted?

An adult Great Horned Owl and an owlet sit in a nest in Rochester on March 13, 2021.
iNaturalist user loretta46
An adult Great Horned Owl and an owlet sit in a nest in Rochester on March 13, 2021.

Owls calling

After a month of suspiciously quiet evenings, staff phenologist John Latimer was relieved to hear his local Great Horned Owls hooting in the evening on Monday, Feb. 5.

“You know, typically the Great Horned Owls should be on their nests right now: they should be sitting on eggs,” he explained. “So, I’m not sure what this was all about, whether it was just checking in with home; a little call to the house to say ‘Hey, Mom, I just caught a rabbit – I'll be back in a minute,’ or what the whole song and dance might have been about. But it was good to hear some owls calling.

“Over the last couple of weeks, we’ve had some concern. Well, not all of us – I'm sure you probably didn’t - but I did. I was a little concerned that something might be amiss with the owls; in spite of this really warm weather, they weren’t doing a lot of chatting, at least around my house. So, it’s good to hear there are some still out there,” John continued. “Good for me. Bad for the rabbits.”

John’s joy was compounded when his good friend Greg reported that he, too, heard Great Horned Owls calling in late January.

Greg also heard – and saw – Minnesota's tiniest owl species, the Northern Saw-whet Owl. These owls are so little, they only eat half a mouse at a time! (One unfortunate - but ambitious - saw-whet owl was found dead after a failed attempt to swallow a deer mouse whole.)

These owls make a distinctive call that sounds like a truck backing up: a repeated, rhythmic “too-too-too.”

Another warm month

January was warm, but not so egregiously as December – at least in terms of degrees over average. There was only one week of cool temperatures, and even that cold snap was gentle in the context of Minnesota winters.

There also hasn’t been much snow. For comparison, 14 inches of snow lay on the ground in Grand Rapids on Feb. 6 last year; this year, the ground is nearly bare.

To tap or not to tap?

Sap is running down the trunk of John’s backyard silver maple tree. John didn’t hesitate to sample it and found it to have a slight sugary taste. (Silver maple sap isn’t as sweet as sugar maple sap, but still has a slight sweet flavor.)

A bucket hangs from a spile on a maple tree. A clear tube directs the sap from the spile into the bucket. In the background, a large metal pan sits on a brick stove. There is snow on the ground.
Charlie Mitchell
A sap bucket hangs from a spile on a maple tree in Marine on St. Croix.

The temperatures rose above freezing during the day and dipped below at night over the past few weeks, cueing maple trees’ roots to send energy in the form of sugar up to the tips of the branches. There, it can be converted into flowers, leaves, and new spring growth.

In typical years, we don't see those temperatures until March or April, when warm days and cool nights create the perfect conditions for the sap run. This when maple syrupers put out their buckets and commercial operations run their tubing.

2024 is different. Just last week, John’s friend in Deer River was gifted a jar of maple syrup - syrup made from sap harvested in January.

With these odd conditions, maple syrupers are left with a conundrum: should we harvest this early sap, or not? Will it hurt the long-term health of our trees? Here are some of the issues at hand:

  • Pros:  
    • The quality of this sap is similar to the usual sap that runs in early spring, according to the Long Lake Conservation Center’s measurements.  
    • Tapping mature trees is harmless under normal conditions, and little evidence exists that tapping during ‘bad’ seasons produces adverse effects.  
  • Cons:  
    • The drought last summer will have stressed the trees, leading to less sugar stored in their roots. This may make them less capable of tolerating the loss of stored energy to tapping.  
    • In addition, the lack of snow has left shallow roots vulnerable to freezing, as well as limiting the amount of water available to the tree.  
    • If the leaves and flowers develop too early and are killed by frost, the tree must pull from its energy stores again to produce new leaves. This would further deplete its energy stores.  

John is weighing all these factors and hoping to consult with some experts this week: he’ll update us on his findings during next week’s program.

Woodpeckers drumming

While we’re staring at our spiles with uncertainty, the woodpeckers have no qualms about tap-tap-tapping on the trees. Downy and Hairy Woodpeckers are busy with the beginning of breeding season – drumming on trees, driving off rivals, and displaying for potential mates.

John described one pair of Downy Woodpeckers who danced in an odd spiral up and down the trunk of an ash tree. The birds remained about three feet apart and on opposite sides of the trunk but were clearly moving in tandem. After a while, they left the ash tree and flew to a balsam, where they were joined by a third bird. John isn’t quite sure what the sexes of the birds were, but he guesses that they were two males pursuing the same female.

Once they form successful mating bonds and hash out the boundaries of their territory, woodpecker couples will begin raising families in March or April.

White-breasted Nuthatches, Northern Cardinals and Black-Capped Chickadees are also busy with nesting preparations: listen for all three singing their unique breeding songs, particularly in the morning. In March, Red-breasted Nuthatches will join the chorus.

Chickadees will nest in April or May; get your nest boxes out now if you’d like to provide a home for a young family!

Nestling noise

As any parent knows, a hungry baby can shriek far more loudly than their tiny body size might suggest. While it’s an effective tactic for getting some food from Mama and Papa, all that noise is dangerous for a helpless baby living in a forest full of predators!

Two nestling Pileated Woodpeckers reach their heads out of the nest cavity to beg for food from their papa. This nest was photographed on June 17, 2023 in Roseville.
iNaturalist user chriskm
Two nestling Pileated Woodpeckers reach their heads out of the nest cavity to beg for food from their papa. This nest was photographed on June 17, 2023 in Roseville.

For birds, this evolutionary dilemma has produced some interesting habitat-specific results. For cavity-nesting birds, being loud is the more successful tactic. With the protection of a fully enclosed nest, most hungry predators can be easily driven off: thus, being a loud, well-fed baby wins the day.

“If you’re a squirrel coming in for a baby bird, you’ve got to breach that hole in the tree. You’ve got to stick your face in there and defend yourself,” John explained. “And of course, if Mama’s home or Papa’s home, they’re going to leaves scars on your forehead for sure... If you look at a Hairy or a Pileated Woodpecker, I would think that a couple of good blows from that beak into the face of a squirrel would be enough to discourage the squirrel forever.”

“So, baby woodpeckers are loud around their nests,” John continued. “And that may not be for a month or two, but if you’re out in the woods and you hear screaming from the nest, it’s woodpeckers.”

In contrast, cup-nesting birds (Blue Jays, American Robins) have very quiet nestlings. Their nests are exposed, giving predators multiple avenues of attack and reducing the birds’ ability to defend themselves. This situation gives an evolutionary advantage to quieter nestlings that wait to beg until the parent is close by.

Other warm winters

Using a few key phenology markers, John determined nine years in his 40-year records that had markedly early springs: 1987, 1990, 2000, 2005, 2010, 2012, 2015, 2016, and 2020.

The spring of 2020 stood out because it was such an early spring following a snowy winter. In that year, the ground wasn’t bare until April 5. (In other early springs, the snow melted much earlier: March 23 in 2009, March 15 in 2011, Feb. 7 in 2015, and Jan. 28 in 2000.)

The ‘highlight reel’ from spring 1987 included:

  • Feb. 15: Tulips blooming 
  • Feb. 22: Crocuses blooming 
  • Feb. 27: Beaked hazel in flower 
  • March 1: First American Robin (its average date of arrival is March 25) 
  • March 7: First American Kestrel (its average date of arrival is March 25), and the first Comptons tortoiseshell butterfly (average April 9) 
  • April 7: Wood frogs singing (average April 16) 

John, anticipating another early spring in 2024, is keeping an eye on the south sides of structures for tulips and crocuses emerging.

“I don’t expect any of the [summer] birds to be back until probably very early March. But if it stays warm like this, we could have a year when the robins and the kestrels and the woodcock and the killdeer and – oh gosh – the Red-winged Blackbirds, Red-tailed Hawks... All of those should be back really early in March if the weather continues.”

As if John isn’t monitoring enough phenological events, he’ll also be listening for wood frogs calling. They typically begin their chorus around April 16, but he’s heard them as early as March 21 (in 2012).

Always expect surprises

However, John’s far too seasoned a phenologist (get it?) to make any strong predictions this early in the year. “It can change in a hurry: we could get a big snowstorm in here. We could get cold weather. All of that’s possible, but not likely,” he said. "We will keep an eye on things and let you know how we’re doing.”

That does it for this week! For more phenology, subscribe to our Season Watch Newsletter or visit the Season Watch Facebook page.

Funding for this project was provided by the Minnesota Environment and Natural Resources Trust Fund as recommended by the Legislative-Citizen Commission on Minnesota Resources (LCCMR).

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Charlie Mitchell (she/they) joined the KAXE team in February of 2022. Charlie creates the Season Watch Newsletter, writes segment summaries for the website, and coordinates our Engaging Minnesotans with Phenology project. With a background in wildlife biology, she enjoys learning a little bit about everything, whether it's plants, mushrooms, aquatic invertebrates, or the short-tailed shrew (did you know they can echolocate?).