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What is phenology, and why bother?

Pine Marten
Photo by iNaturalist user gonodactylus.
American/pine marten (Ojibwe: waabizheshi)

Why phenology?
Phenology is all about seasonal changes, and boy, are Minnesotans tuned in. It's impossible to ignore the seasons here: we treasure our summer escapes to lakes and rivers, admire the fall leaves, and bust our backs shoveling heavy snow.

Despite our collective interest and enjoyment of our seasons, phenology as a biological study remains far from most Minnesotans' radar. This is partially because it's poorly named: the word 'phenology' comes from the greek 'phaino,' which means "to appear" (for instance, as daffodils appear in the springtime). Shockingly, most of us don't have a working knowledge of Greek, so that doesn't do much good!

Phenology can be hard to define in plain old English, and many different definitions exist. Our staff phenologist, John Latimer, describes phenology as the "rhythmic biological nature of events as they relate to climate." I, your friendly local phenology coordinator, think of it like this: phenology is a set of questions we ask the natural world daily. Those questions are: "Who or what is out there right now? What are they doing? Finally, how have those things changed over time?"

For instance, as I look out my window in West St. Paul today, there's still snow on the ground in patches. I can hear a Canadian goose honking, see an aspen tree with its flowers, and admire a house sparrow building its nest on top of my AC unit. That answers the 'who' and the 'what.' Last week, there were far fewer geese strutting their webbed feet down my street, the aspens flowers were tiny little fuzzy buds, and the house sparrows were still fighting over their nesting territories. Last year, we had had much warmer spring weather, and some leaves were already appearing. A decade ago, I wasn't living here, so who knows? The U of M might have records! That answers 'how have things changed over time?'! (Note that "time" can encompass many different scales, from a few hours to centuries). All of this is phenology!

If you want a deeper understanding of what phenology is, let's look at those 'core questions' individually.

Who or what is out there? 
Lots of things change with the seasons, especially here in Minnesota! We have a vibrant seasonal rotation of plants and wildlife. Many of our iconic species are only present in the state in summer: loons, bats, butterflies, and more leave the state during the cold months. Some species that remain in the region still aren't observable in winter (frogs, bears, and woodchucks, for example). Many of our favorite plants can't be seen during the winter, such as the milkweed, the lilac, and the sunflower. With all this change, it's definitely worthwhile to take a look at who's out there! There is also a what component. Is there snow on the ground? If so, how much? Are the lakes free of ice? What's the temperature? What are water levels like? All of these are essential phenological questions.

What are they doing?
Personally, this is my favorite of the three questions. I'm a sucker for wildlife behavior, and seeing the full range of seasonal changes in my favorite species is never-ending fun! For instance, let's think about the chickadees that hang out at my parents' birdfeeder. All year, they show up to snack on the oiled black sunflower seeds my parents have graciously been providing for them for 37 years. They look exactly the same throughout the year, and their abundance doesn't appear to change. However, back in the forest, it's a dynamic situation! Depending on the season, they might be selecting a nest site, raising chicks, or caching seeds away for winter. (Sidenote: Chickadees can store up to 80,000 individual seeds in different spots. They can go back months later and find all those caches by memory- I can't find my way to the DMV without google maps!)

While the chickadees are out there flockin' around, the resident deer may be feasting on delicious new leaves or struggling through heavy snow. Barred owls might be hunting the summer frogs or trying to catch voles beneath the snow. It's not just the wildlife changing their habits to suit the season; deciduous trees drop their leaves in fall and grow new ones in spring. Spring wildflowers have to time their flowering carefully to capitalize on the increasing sunlight before the deciduous trees leaf out and shade them; however, flowering too early puts them at risk of a cold snap. Even pine trees, which we consider unchanging by season, time their pollen release and seed dispersal carefully!

How is it different from last week/month/year?
This is where phenology truly hits its stride. Both the 'who' and the 'what' can be weather dependent. For instance, deer may use roads more during periods of deep snow, or the warming weather may have brought the first heron of spring into town. In addition, seasons can transition differently from year to year; as I'm writing this in 2022, we've had one of the coldest springs on record. Finally, the climate itself is changing. Phenology allows us to track these changes by observing variations by decade.

To summarize:
When it comes down to it, phenology is the study of seasonal changes in plants and animals and how those changes relate to climate. With each season, plants and animals transition through their life cycle stages. You can detect this happening with your own senses. For example, anytime you notice spring daffodils emerging, the fall leaves changing color, or the red-winged blackbirds arriving in the spring, you observe phenology! All you have to do is write it down: then, boom! You've become a phenologist. One of the many things I love about phenology is that it is one of the most accessible of the biological sciences. You don't need a special degree, the ability to identify a bunch of birds, or an hour to devote every day to study phenology. Phenology is something anyone can do, in any place, at any time of year. You can simply look out your window and write things down; if you do, I can guarantee it will enrich and enhance your life.