other By: Anthony Hauck | October, 21
Story by Anthony Hauck, cover photo by Steve Oehlenschlager
Nesting cover rules, while the difference between trees and “woody cover” is distinct “To those first European explorers and colonists, grassland probably meant snug meadows, deer parks, and pastures safe behind fence and wall. They had no basis for even imagining wild fields through which a horseman might ride westward for a month or more, sometimes traveling for days without sight of trees." — John Madson, Where the Sky Began
Grasslands and trees have waged an epochs-long tug-of-turf war in the middle of this continent. Tallgrass, midgrass and shortgrass prairies have staked rightful claims. Trees, worthy adversaries, continually seek to advance and convert this open land into forest.
But the tilt has shifted again since the great European migration.
The early encroachment was seemingly benign: Tree seedlings volunteering in new carveouts as virgin prairie was broken, scarred and settled.
The extinction of bison and retirement of wildfire, both tree suppression specialists, reoriented the ecosystem and paved the way for tree proliferation.
And finally came tree plantings — well-meaning efforts that yielded unintended and even invasive consequences.
The hastened arboreal assault is more than aesthetic. To the ring-necked pheasant, a grassland bird, each root, sapling and crown is not just a victory for the rival side, but potentially spells doom, a landscape alteration no less ominous than a plow or pavement.
The essence of prime prairie upland habitat is defined as much by what isn’t there — trees — as its mix of grasses and forbs. But trees can become occupants of hearts and minds as much of the land, ecosystem be damned.
“It’s funny. Wherever trees should naturally occur, people seem to try their hardest to get rid of them. And wherever trees shouldn’t occur, they try their hardest to plant them,” said Rachel Bush, a biologist and Pheasants Forever’s state coordinator in North Dakota.
That includes her home ground, the most treeless state in the union.
“I see a lot of tree plantings in the name of pheasant habitat,” said Bush, noting that in many instances, they do more damage to pheasant populations than would having no trees at all.
Bush says tree rows often break up big blocks of grass, essentially inviting predators to an upland species smorgasbord: “Those trees that we as humans hunt — we’re a predator — are the same things that other predators use too.”
Foxes and coyotes systematically stalk up and down tree rows. Avian predators such as hawks and owls use trees as hunting perches and nest sites. But the drain on pheasant nesting — that critical, once-a-year opportunity to grow the pheasant population — is most negatively impactful.
Nest raiders like skunks and racoons use tree plantings as den sites, headquarters for their spring gorge. Crows set up shop in tall conifers, nesting themselves while preying on eggs. This adds up to reduced pheasant nesting success near tree sites.
That’s at the field level. But research from Nebraska brings greater statistical significance to the thorny relationship between pheasants and trees. Assessing Landscape Constraints on Species Abundance: Does the Neighborhood Limit Species Response to Local Habitat Conservation Programs? indicated pheasant populations respond negatively to the number of trees at scale. A landscape constituted with as few as 15 percent trees severely limited pheasant numbers, according to the 2014 report.
TREES VERSUS WOODY COVER
The fact that large deciduous and coniferous trees are a low-grade habitat for pheasants can be a difficult concept for pheasant hunters to grasp.
“Pheasant hunters walk tree rows, shoot a pheasant out of there and think, wow, trees must be good for pheasants,” Bush said.
In Minnesota, tree removal is an ongoing and often highly visible part of the prairie restoration scene, occurring on Wildlife Management Areas (WMAs) and Waterfowl Production Areas (WPAs). Tim Lyons, Upland Game Research Scientist with the Minnesota Department of Natural Resources, says area wildlife managers in his state regularly field hunter concerns regarding such projects.
In making such simple associations, Bush and Lyons find hunters bypass what pheasants need at the ground level and fail to make the distinction between trees — growth higher than 15 feet — and the much more desirable “woody cover.”
Woody cover — comprised of dogwood and willows (what biologists classify as shrub carr), shelterbelts, dense herbaceous vegetation, brushy woodland edges or pine plantations — is an important thermal (or winter) cover component.
In some areas, woody cover may provide the only protective thermal cover available when winter snows fall and winds blow. But for the large swath of pheasant country that overlays with the Prairie Pothole Region, the preferred winter cover for pheasants is emergent wetland cover, or cattail marshes.
“While woody cover does provide some of that emergency winter cover, for the most part, pheasants in North Dakota get by with the natural woody draws we have and the eastern cattail sloughs,” Bush said. The same goes for South Dakota as well as Minnesota’s pheasant range.
According to the National Wild Pheasant Conservation Plan, pheasants remain in or near nesting areas in grassland habitats during mild winters, moving to cattail habitats only when those grasslands are snowed in. In fact, it’s not uncommon for warm-season grasses like switchgrass, big bluestem, little bluestem and Indian grass to provide adequate thermal cover in normal winters.
It’s only in extreme winters, when wind and snow conspire to fill in those cattails, that pheasants seek woody shelterbelts. The plan highlights research from the turn of this century that categorizes woody habitats as “emergency cover,” only utilized by pheasants when nothing else was available.
FOCUS ROOSTER RESOURCES
Adding insult to habitat injury is this: While fragmenting uplands and creating predator opportunity, tree plantings take up space that oftentimes may be better served as valuable nesting cover. Thermal cover is an important piece of the pheasant habitat mosaic, but it ranks a definite second to available nesting cover as far as a population limiting factor.
Lyons says when you consider that annual production is largely what determines the strength of the pheasant population (the birds available for you and I to hunt in fall), and that the available research overwhelmingly ties the proximity of tree edges to decreased nesting success and even nesting avoidance, the picture becomes clear:
“We need to be more focused on what benefits the population,” Lyons said, “In today’s landscape, that’s unquestionably nesting and brood-rearing cover. It all comes down to nesting success.” And trees hinder nesting success.
Bush, who has witnessed 1.5 million Conservation Reserve Program (CRP) acres of prime nesting habitat vanish in her state in the last decade, notes that what matters in this habitat ebb is optimizing remaining upland acres.
“When we remove single-row tree belts from perennial nesting cover or replace tall trees with pollinator plantings or native shrub blocks, we immediately make those corridors way more valuable to wildlife,” she says.
Bush is far from anti-tree. But from her prairie perspective, she stresses the importance of thermal cover strategically placed and in the right form: “If you’re going to plant, focus on large blocks, and at least 15 rows. Let’s make sure that it’s smart, that it’s the right species (native), that it’s wide enough, and that it’s not breaking up large blocks of nesting cover.”
And, as Madson notes in his prairie treatise, there’s something to be said for turning into the wind and embracing the prairie not for what it isn’t, but everything else it is:
The world had opened into a light-filled wilderness of sky and grass that would open its people as well, freeing them of certain dogma, breaking old institutions, and shaping new ones to fit the land. Each wave of American settlement from east to west had progressively deepened New World naturalization, and no settlers were altered more deeply than those who drew away from the treelands and became true grasslanders at last.
TREE PLANTING DO’S AND DON’TS
DO consult your local Pheasants Forever Farm Bill Wildlife Biologist at www.pheasantsforever.org/Habitat/findBiologist.aspx, or other natural resource professional.
DO consider substituting a warm-season grass mix for thermal cover, rather than planting trees.
DO mimic natural woody areas with native species and avoid invasive species such as Russian olive and Siberian elm.
DO plant as close as possible to a reliable food source and consider only shrub or low-tree plantings that provide an additional food source — buffaloberry, chokecherry, crabapple and American plum, for example.
DO plant low-profile tree and shrub species in a minimum of 15 rows and, if possible, create a block planting that will beat winter snows and winds to provide thermal cover.
DON’T plant trees in or around nesting cover.
DON’T overdo a tree planting. A rule of thumb is 5 acres of trees per every 100 acres of grassland habitat.
DON’T plant trees in native prairie, an endangered ecosystem. Songbirds, prairie grouse and other native species depend on native prairie for survival.
DON’T fragment nesting cover with woody cover when preferred thermal habitat like cattails may already be available.
DON’T plant 3-, 4- or 5-row tree belts for the benefit of wildlife. They fill with snow early in winter, rendering them useless as thermal cover.
Sources: Pheasants Forever, Ducks Unlimited, U.S. Fish and Wildlife Service, Natural Resources Conservation Service, North Dakota Game and Fish Department.