critter condossnags along farm fence rows and adapt well to wooden fence posts and nest boxes too....

Snags. By night, they look ghostly in themisty, moonlit darkness. In reality they

teem with life. Over 70 kinds of Wisconsinmammals, birds, reptiles and amphibians, notto mention swarms of insects, spiders,millipedes and other invertebrates usesnags…dead or dying trees. These crittercondos provide den, nest and feeding sites, aswell as sites for food storage, perching,preening and courtship rituals. Thispublication illustrates the variety of dead woodthat benefit wildlife and the ways you canmanage for it.

On a sunset stroll through your woods, you find aforest full of activity...full of life…a snowshoe harebounds for cover, a red squirrel scampers up abalsam fir, a blue jay scolds from a branch above. Asthe curtain of darkness falls, your senses heighten.Your nose intercepts the pungent, earthy odor of leafmold, fungi, and rotting wood drifting on the breeze.Your ears snatch a few “who cooks for you, who cooksfor you all?” notes of a barred owl. Suddenly, yousense movement overhead! Turning, your peripheralvision catches the floating form of a flying squirrel asit leaps and glides from a snag. The smooth, barklessskeleton of this dead tree standsstark and whitewashed in themoonlight. It’s then you realize thatin your forest, even dead things haveappeal…a life of their own….

Wildlife and Your Landa series about managing your land for wildlife

Critter CondosManaging Dead Wood for Wildlife

Just as the style, size andlocation of housing affectwhere you live, the style,size and location of deadtrees determine whatkinds of wildlife you’llfind in, on or underthem. For example,snags—which arestanding dead anddying trees —make

good homes for cavity nesterssuch as woodpeckers, bluebirds,

nuthatches and squirrels. Downed trees orlogs provide great hiding places for sala-manders, snakes, deer mice, weasels andchipmunks. If large enough, these can makegood bear dens. Riverside snags, with theirtangled mass of gnarled roots provide shelterfor brown trout and burrowing sites formuskrats. Their upper limbs may be used fornesting by herons, egrets, bitterns andcormorants. When managing your land forsnags, consider where you live in the state.This will determine what wildlife are mostlikely to inhabit the dead wood on your land.The more you know about dead wood and thetypes of wildlife that depend on it, the betteryou’ll be at providing homes for wildlife—inessence, you’ll be moving one step closer tobecoming a wildlife realtor!

GY Style: Hard vs. Soft Snags

Snags come in two styles: hard and soft.Both are important to wildlife. Hard snagshave rotten centers, a solid exterior andusually a few limbs attached—they make thebest den trees. As snags decay, the woodsoftens and becomes punky and the limbsgradually fall off. Soft snags, with theirpulpy wood fibers, make good forage sites forinsect-eating birds and excellent nest sitesfor woodpeckers and songbirds such asblack-capped chickadees.

A tree’s characteristics determine its snagand cavity potential. For example, sugarmaple, elm, black and white oak, hickory andbutternut are excellent cavity trees withhigh wildlife value. These hardwood treesgrow to large sizes, decay slowly, andproduce hard, upright and long-lived snags.The beech tree, common along LakeMichigan and Green Bay, also makes a goodcavity tree because it’s prone to heart rot.

Softer trees, like aspen and birch, have shortlifespans and rot quickly. These rapidgrowers make superior soft snags of highvalue to wildlife since they produce cavitiesmore quickly than hardwoods and providehabitat for swarms of insects which feedmany forest songbirds.

Snags of medium value to wildlife comefrom white ash, basswood, red maple, whitepine, red oak, yellow poplar, box elder, blackcherry and black walnut. Coniferous snagsgenerally do not last as long as hardwoods,though pine and tamarack make excellentnest and perch sites for osprey when locatednext to water.

2 Wildlife and Your Land

Ever “snag” your line while fishing? As frustratingas it is to lose a lure, every good angler knows thatfallen logs in a pond or stream provide trout, bassand other fish with a sheltered, shady place to rest

and feed. Downed logs inor near water are

especially vital andshould be sparedat all costs. Andwhile you’recutting your linefree, you’llprobably startlea few turtleslazily sun-bathing on a

log…kerplop.....

Style

SizeLocation

Y

The Critter’s Criteria

GY Size: Small vs. Large Snags

Human condos come in all sizes and so docritter condos. In general, the larger thesnag, the more kinds of wildlife it can host.While small snags are important in theirown right, they can only host small creaturessuch as the red-breasted nuthatch, downywoodpecker, house wren, bluebird and white-footed mouse. But large snags can suit smalland large wildlife such as pileated wood-peckers and raccoons. Imagine the size of thelog den needed for a black bear!

The best den trees,which can be eitherliving or dead, are15 or more inches in

diameter at breastheight (DBH) with den

openings 4 inches ormore. However, pleasedon’t discount thesmaller den trees. If you

have large den trees onyour property, keep them!

Also hang on to “wolf”trees. These forest giants

have large sprawlingbranches and great potential

for cavities. In addition, thesetrees are often abundant nut andfruit producers.

If you are interested inmanaging for larger birds andmammals, you will need topreserve some of the largertrees…just let them die of “old

age.” The pileated wood-

pecker, Wisconsin’s largest woodpecker,needs a tree at least 20-22 inches DBH inorder to excavate a nest cavity. Pine martensalso need very large trees.

GY Location: Forests, Waterwaysand Fields

Snags are most commonly associated withforests. Many a forest mammal from bat tobobcat, bear, pine marten, porcupine, redsquirrel, and gray fox use snags for dens andlookouts. So do many forest birds. Wood-peckers are the primary excavators. Theydrill out new homes in snags. When aban-doned, these cavities become residences forother creatures like saw-whet owls, nut-hatches and great-crested flycatchers.Besides woodpeckers, the only other birdthat is a primary excavator is the black-capped chickadee. However, these diminutivebirds, which lack the powerful chisel-likebeak of woodpeckers, can chip out a cavityonly in soft snags.

Snags located near waterways and wetlandsalso offer great benefits to wildlife. Woodducks, hooded mergansers, common golden-eyes and buffleheads need tree cavities fornesting. Herons, egrets, eagles and ospreysbuild their nests high atop snags standing inor near water. Snags also serve as lookouttowers for keen sighted fish-eating birds,such as belted kingfishers.

Snags located near open fields attract sometypes of hawks and owls. From high atoptheir lookouts, these birds use telescopicvision and radar-like hearing to detect mice,rabbits, squirrels and other prey. The flicker,

Wildlife and Your Land 3

Larger cavity dwellers need large trees. The pileatedwoodpecker needs a tree at least 20-22 inches in diameterin order to excavate a nest cavity. Small cavity dwellers,like this mouse, can utilize both large and small trees.

unlike its woodland dwelling woodpeckerrelatives, prefers to nest in snags alongwoodland edges bordering farm fields oropen grasslands. Kestrels and easternbluebirds will often move into old flickerholes. Colorful bluebirds frequently nest insnags along farm fence rows and adapt wellto wooden fence posts and nest boxes too.

Even backyard snags can attract housewrens, black-capped chickadees, red-belliedwoodpeckers, and flying squirrels. If a snagposes no threat of dropping large brancheson people—leave the snag in place. If youmust cut a tree, leave it lie as a log.


Downed Wood: Let Sleeping Logs LieOnce a snag has toppled over it doesn’t lose its value to forest wildlife.Downed and rotting logs provide moist and earthy homes for

salamanders, moles, shrews, earthworms, millipedes,centipedes and more! Squirrels will cache their food

within the soft fibers of fallen trees. Hollow logscan be used by foxes as winter dens. The next

time you go camping watch howchipmunks use downed logs asrunways to scurry through the forest,sprinting from log to log. If it’sspringtime, listen for drummingruffed grouse which perform theircourtship dance atop mossy logs.

Toppled trees also are importantin forest regeneration. Some

rotten logs, known as nurselogs, provide a good growingmedium, rich in nutrients,for tree seedlings to get a

healthy start in life.

Ruffed grouse

Birds Food Nest Perch

Wood Duck Y YCommon Goldeneye YBufflehead YHooded Merganser Y YCommon Merganser Y YGreat Blue Heron Y YBlack-crowned Night Heron Y YDouble-crested Cormorant Y YCommon or Great Egret Y YBelted Kingfisher YTurkey Vulture Y YMerlin Y YAmerican Kestrel Y YBarn Owl Y YScreech Owl Y YBarred Owl Y YSaw-whet Owl Y YBald Eagle Y YOsprey Y YRed-tailed Hawk Y YChimney Swift YRuffed Grouse YCommon Flicker* Y Y YPileated Woodpecker* Y Y YRed-bellied Woodpecker* Y Y YRed-headed Woodpecker* Y Y YYellow-bellied Sapsucker* Y YHairy Woodpecker* Y Y YDowny Woodpecker* Y Y YBlack-backed Woodpecker* Y YThree-toed Woodpecker* Y YGreat-crested Flycatcher Y YTree Swallow YPurple Martin Y YBlack-capped Chickadee* Y Y Y(soft snags only)Boreal Chickadee* Y Y YTufted Titmouse YWhite-breasted Nuthatch Y YRed-breasted Nuthatch Y YBrown Creeper YHouse Wren Y

Birds, continued Food Nest Perch

Winter Wren YBewick’s Wren YCarolina Wren YEastern Bluebird Y YProthonotary Warbler Y

Non-native Pest Birds

Starling Y Y YEnglish Sparrow Y Y Y

Mammals

Opossum YBig Brown Bat YLittle Brown Myotis Bat YSilver-haired Bat YEastern Pipistrel YRed Bat YHoary Bat YBlack Bear Y YRaccoon YPine Marten YFisher YMink Y(under logs)Gray Fox YBobcat Y YLeast Chipmunk Y YEastern Chipmunk Y (logs)Red Squirrel Y YGray Squirrel Y YFox Squirrel Y YSouthern Flying Squirrel Y YNorthern Flying Squirrel Y YDeer Mouse Y (stores food) YWhite-footed Mouse YPorcupine YSnowshoe Hare Y (hollow logs)

Reptiles and Amphibians

Most Salamanders Y (under logs)Tree Frogs Y


Wisconsin Wildlife Dependent on Snags

*Primary Excavators: Primary excavators drill their own cavities out of dead wood. Later these cavities can be used by other wildlife.


The Life Cycle of a Dying Tree

The decline of a tree begins when heart rot fungi invade the tree through a wound to

the tree’s bark. Slowly, the tree’s corebegins to rot—

—barren branches appear,perhaps a good site for an

eagle nest or perch forbroadwing hawks and

flycatchers. Insectsand beetles feast.

Bark loosens.

bluejay

bald eagle

broadwingedhawk

wood-boringbeetle


Woodpeckers soon follow, in search of food and potential home sites.Using their specialized bills, these birds chip away at the softened wood

to create a cavity large enough for nesting. They raise their young, feedon the insects harbored within the decaying wood, and move on. The

empty cavity then becomes home to another creature—perhaps an owl,squirrel, bluebird or bat.

Eventually, the battered ghost of atree topples, or remains as a soft

stump, maybe half its originalheight. Carpenter ants invade, a

healthy lunch for a passing bear or coon.Salamanders, snakes and mice move

in…while a nearby hawk, perched highupon a neighboring snag,

takes note.

The tree decays furtheruntil new plants and

mushrooms take sproutin the remaining

organic matter.Life goes on….

downywoodpecker

flycatcherred

squirrel

bat

browncreeper

deer mouse

salamander

chickadee

carpenter ants

black bear


Insect CafeteriasSnags teem with life. So, too, do diseased andfallen trees. Their loose bark and many nooksand crannies shelter a multitude of tinycreatures. Just turn over a rotting log andwatch the insect activity. While the swarming,creeping, slithering tangle of ants, spiders,millipedes, centipedes, beetles, worms andslugs may seem unsettling to you, this insectcafeteria provides a nutritious lunch for manybirds, mammals, reptiles and amphibians.

For example, pileated woodpeckers actively seek out elm and aspen trees infested with woodboring insects, and black bears lap up ants found in rotting logs. Brown creepers, smallbrown birds with curved beaks, search for insects hidden under loose bark as they spiral upthe trunk. Other cavity dwellers are voracious insect eaters, though the insects they eat maynot live in dead wood. For example, a house wren can feed 500 insects to its young everysummer afternoon and a swallow can consume 1000 insects every 12 hours. In fact, thesebirds act as natural pesticides and help keep insect populations in check. So hang on to deadwood, it’s good for wildlife and it does not always pose a threat to your woodland. For years,however, this was not the prevailing attitude.

In the past, loggers cut down all dead trees during timber harvests because they had limitedvalue as timber, harbored forest insect pests, and were potential fire and safety hazards.Subsequently, cavity nesting bird populations have declined in recent years due to a loss oflarge trees with natural cavities.

Today, loggers, foresters and wildlife managers work together to protect these valuable treesand the insect cafeterias they harbor. It is now understood that insects and disease arenatural parts of the forest and contribute to its stability, productivity and diversity of life.

A saw-whet owl takes up residence in a cavity thatwas earlier excavated by a woodpecker.

Snags located next to waterserve as lookout towers forthe fish-eating kingfisher.

Seek Out Snags

Consider this, it takes about 40 yearsbefore completely cleared land becomessuitable for most woodpeckers andother snag dependent wildlife. It takesabout 80 years before trees can supportthe larger cavity dwellers like raccoons

and pileated woodpeckers. So, before you cutfirewood or implement a timber standimprovement plan, you should identifyexisting and future snag and den trees.

Snags in advanced stages of decay are easyto identify—they stand out like skeletons.Diseased trees are a little harder to spot.Look for signs of injury or a rotten core—fungal heart rot. Dead branches, rottingbranch stubs, fungal growth, old wounds,scars and discolored or soft bark are all signsof a dying tree. Also, look for woodpeckerholes. Woodpeckers actually seek out treeswith rotten cores. Always note the wolf trees.

Create More Dead Trees

Look around you. If you find fewsnag or den trees on your property,create them yourself using somesimple techniques.

To create a snag, select a living tree that’sover a foot in diameter—the bigger, thebetter. Also, try to select a tree that’s eitherdiseased or severelydeformed, or selectthose that arecrowding morevaluable trees thatyou would like togrow larger. Goodtrees for creatingsnags include sugarmaple, black oak,white ash, elm andbasswood. Take anaxe and cut away a3- to 4-inch band ofbark around theentire circumferenceof the trunk. Makesure you remove thebark and cut wellinto the sapwood.This technique isknown as girdling. It disrupts the flow ofnutrients within the living layer of the treefound just underneath the bark. This causesthe tree to die, and eventually become asnag.

To create a den tree, cut off a 4- to 6-inchlimb about 6 inches from the trunk, or chopout a section of bark 6 X 6 inches at the baseof a suitable wolf tree. These open woundsshould allow fungal disease to enter the tree


Girdling disrupts theflow of nutrientswithin the living layerof the tree found justbeneath the bark.

Managing for Dead Wood

When a woodpecker begins pecking away on a tree, it may be inthe early stages of decay. Mark it as a future snag tree. Also lookfor dead branches and stubs, fungal growth, old wounds, scarsand discolored or soft bark.

1 2

and start the decay process. A natural cavitywill form over the years. Elm, ash, boxelder,maple and basswood are especially prone toform natural cavities.

Since it takes several years for thesepractices to create suitable nest and dencavities, you may want to build and placenest boxes for birds and mammals until treesbecome available. Please realize, however,that properly locating and maintaining nestboxes is extremely important. Also, not allcavity nesters will use nest boxes.Chickadees, house wrens, wood ducks,purple martins, and eastern bluebirdsreadily accept them, whereas woodpeckersprefer to excavate their own nest cavity.

Save Snags WhenCutting Timber

If you are managing yourwoodland for wildlife and timberproduction, consider thefollowing rules of thumb:

Preserve about one to six hard snags peracre and as many soft snags as possible. For every 20-acre woodlot, leave thefollowing: four to five snags or den treesover 18 inches DBH, 30 to 40 snag or dentrees over 14 inches DBH, and 50-60snags over 6 inches DBH.Save at least one tree of any size per acreshowing potential for den or snag treedevelopment, especially those with brokentops, woodpecker holes or wounds. Never cut a wolf tree; they make excellentden trees.Check for wildlife before cutting a tree;avoid cutting inhabited trees.Leave most snags evenly spaced, thoughinclude a few patches where they areclumped together. Leave fallen snags on the ground toprovide food and cover for wildlife. Cut green, rather than dead wood forfirewood and cure for several years.


Management Techniques in ReviewWhen managing your land for dead wood, keep in mind the following rules of thumb:

The Critter’s Criteria:

Size: Bigger snags can accommodate more wildlife.

Style: Maintain hard and soft snags.

Location: Location often determines what wildlife will use it.Where you live in the state is also important.

Management:

Always plan for future snag and den trees.

Girdle diseased or deformed trees to create snags and

Manage for snags when timber cutting

3


Notes

Wildlife and Your Land Staff: Mary K. Judd, Project Director;Diane Schwartz, Project Assistant; Todd Peterson, Agriculturaland Rural Land Use Specialist. Graphics and layout, KandisElliot. Funding for this project was provided in part through theFederal Aid in Wildlife Restoration Act and through the NaturalResources Foundation of Wisconsin, Inc., P.O. Box 129, Madison,WI, 53701. Published by the Bureau of Wildlife Management,Wisconsin Department of Natural Resources, P.O. Box 7921,Madison, WI, 53707.

Federal Aid Projectfunded by your purchase of

hunting equipmentPUBL-WM-222

critter condossnags along farm fence rows and adapt well to wooden fence posts and nest boxes too....

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