I stopped at Blueberry Hill, overlooking the St. Croix just south of Bayport, one afternoon and in perhaps a half-hour happily observed three flowers and three birds, and bright green banks besides dark blue water. I also saw a small ecological scene play out, part of an eternal drama.

The prairie where I walked has never been plowed to the best of anyone’s knowledge. Likely because of fires set by nature and Native Americans, and subsequent settlers who grazed cattle on the grasses, and then young people who parked their cars on it for decades during the twentieth century, it remained treeless and retained some of its native species. Now, thanks to the volunteer efforts of The Prairie Enthusiasts and ownership by the Minnesota Department of Transportation, fire has been reintroduced, and invasive species have been removed. Blueberry Hill remains a rich refuge with an amazing view.

This small slice of prairie is sandwiched between a busy highway and a slope so steep it seems more cliff than hill. I later used a topographic map to calculate the gradient at almost 60 degrees. Railroad tracks run along its base, cut into the bank between the bluff and the water.

I walked along the grassy precipice, an abrupt ridge with the bluff descending into thick trees and brush on one side. Breeze and birdsong nearly drowned out the sound of traffic drifting across 600 yards of soft land in between, blanketed it in a thick cushion of prairie plants.

Sun and water in the middle of May can fuel incredible growth. I was struck by how fertile everything was, while the world was still fairly colorless and quiet a few short weeks ago.

Spring having come and gone, now the short- to medium-height prairie flowers were bold blotches of color amid the rapidly growing grasses. Before the grasses got too high, these flowers took advantage of their moment in the sunlight.

I interrupted something as I approached an oak tree and a clump of bushes. A small bird chased a large bird out of the thicket, and the large bird flew up to the top of a nearby utility pole. The small bird bounced around in the oak branches, agitated and unafraid.

I looked first to the top of the pole and saw it was a female brown-headed cowbird. It pranced around on its perch and stared back at the bushes from where it had been chased. The chaser, the defender, was a clay-colored sparrow (Spizella pallida). Their conflict was part of both species’ genetics. This type of sparrow specializes in shrubby areas in the open, nesting in bushes like these or on the ground.

The cowbird is often maligned, unfairly. It is what’s known as a brood parasite — it lays its eggs in other birds’ nests, and tricks the other parents into feeding and caring for their young, usually at the expense of the host parents’ own chicks. Clay-colored sparrows are one of a cowbird’s favorite marks.

This reproductive strategy can seem deceitful and dastardly through human eyes, but it’s simply an ecosystem in action. The effects of cowbirds on native species is also far less than how humans are hurting most bird species through habitat destruction, pesticides, and more.

Cowbirds are filling a niche in the network of life and death, prey and predators, reproduction and survival. Clay-colored sparrows have learned to live with it well enough that their own species has also survived so far.

I could sense the nests full of the next generation everywhere this week. Birds busy with broods, baby beaks always demanding the next meal. The parents sing and forage, defending territory and helpless chicks, this season the whole point of a year of migration and peril.

Getting back in my vehicle, I leave this determined and disparate pair to their ancient struggle.