Blane Klemek: Predator and prey, a delicate balance in nature
When I was employed as the manager and director of the Wetlands, Pines and Prairie Audubon Sanctuary (now called the Audubon Center of the Red River Valley and Omdahl Arboretum), which is a wildlife refuge and environmental education center near Warren, Minn., one of my responsibilities was constructing, installing and monitoring wood duck nesting boxes — also known as wood duck houses.
I recall one particular wood duck box that was mounted on the little red bridge that crossed the canal waterway next to the center’s wildlife pond.
The wood duck hen inside the nesting box was incubating an impossible number of eggs — 27 in all. Nearly every day, for close to a month, I monitored her progress. And since a wood duck’s incubation period typically lasts about 30 days, I knew any day I would either find egg membranes indicative of a successfully hatched clutch of eggs or, if I was really lucky, observe the newly hatched ducklings either still inside or leaving the nest box.
Since this hen’s nest box was affixed to a support column on the bridge, it was easily accessible. When I checked the box, I would slowly open the side-door — just a crack — and peek inside. As the days wore on, the wood duck hen would sit tight and allow me the pleasure of looking at her. She was a docile and accommodating bird.
One day, as I walked toward the box, I noticed feathers outside the entrance and clinging to the structure. There appeared to be fresh-looking blood smeared around the entrance hole. Somewhat apprehensively, yet fully expecting my discovery, what I found when I opened the box was nevertheless a shock. The hen was there, dead. A predator of some form, probably a mink, had severed the bird’s head and neck and left the lifeless body of the duck behind.
I removed the bird from the box. Its body was cold. I also handled a number of the eggs, checking for any signs of warmth. They, too, were cold. So close were they to hatching that, at first, I was angry the ducklings had missed their chance at life. It seemed such a waste since the predator took so little of its prey, yet took so much potential life.
After further thought, I realized that this, of course, is nature’s way. Without question, I would have much rather seen the clutch of eggs hatch. But the fate of those ducklings and their mother, however cruel you and I deem it to be, lies within a randomness for which we have no control.
That the mink lived another day was good. My perception of waste — the leaving behind of the duck’s body and her eggs — was not waste at all. Perhaps the mink would have returned to finish its meal had I not removed the duck and eggs and cleaned the nest box out.
Perhaps the nest box was merely serving as the mink’s storage container, a cache of food for later consumption. And even if that were not the case, other organisms would have most certainly utilized the bird’s flesh to live another day as well. The nest box would have soon been teeming with carrion beetles, flies and other insects making use of the bird’s flesh.
As wind and fire help renew forests, thus keeping the forest healthy, so, too, is the role of predators on prey populations. Predators assist in controlling populations from exceeding a habitat’s ability to support a population of prey species. And without the predators’ place, life’s delicate balance is sometimes altered to the detriment of the very species they prey upon. White-tailed deer, for example, is an animal that has flourished, in part, because of the lack of abundance of their natural predator, the wolf. Yet without the wolf, deer can overpopulate and over-browse the forest, consequently causing populations of deer to become more susceptible to famine and disease.
Predatory animals are frequently the most misunderstood and ill treated of creatures. Wolves are a case in point. Mostly out of unsubstantiated fears, humans have always persecuted this animal. Indeed, wolves can and do prey on domestic livestock and pets from time to time, but by and large they are predators of wild creatures. Competition for space and resources, including natural resources such as wild deer, has created many problems for wolves and has therefore led to inevitable conflicts with humans.
In the world of waterfowl, for another example, much effort has been made to increase duck populations through upland habitat acquisition and enhancement, wetland restoration, implementing hunting regulations that restrict harvest and seasons and even employing predator control programs.
This is all well and good for waterfowl and other wetland and grassland dependent species wildlife, and by all means such efforts are necessary to maintain and enhance waterfowl populations. Yet, if not for diminishing and fragmented nesting habitat that ground-nesting birds require — ducks, meadowlarks, bobolinks, as well as ground nesting woodland birds — predators and their prey would not be so heavily concentrated within some habitats.
Habitat loss aside, the wood duck hen I discovered dead inside the nest box underscored the mink’s predatory efficacy as much as it emphasized the bird’s vulnerability. All birds are at risk to predators in similar situations.
Indeed, whether it is a sharp-shinned hawk swooping through a backyard bird feeding station to capture a chickadee, or a badger raiding a mallard nest somewhere in the middle of an expansive prairie grassland, all predators, great and small, are hunting and surviving everywhere and every day as we get out and enjoy the great outdoors.
— Blane Klemek is a Minnesota DNR wildlife manager. He can be reached at firstname.lastname@example.org