U.S. Fish & Wildlife Service

Keeping Fire on 

Our Side

Fire Management at 

Balcones Canyonlands 

National Wildlife Refuge
Prescribed 

burns restore 

wildlife habitat 

and healthy 

ecosystem.

FWS photograph

Balcones 

Canyonlands 

NWR

Prescribing Fire 

for a Healthier 

Refuge

Pairing the word “fire” with “health” 

may seem like a contradiction. Yet, 

flames have shaped the ecologically 

rich landscape of Balcones 

Canyonlands NWR over the eons. 

Without fire, the endangered blackcapped vireo’s nesting habitat is at 

risk. Without fire, the prolific Ashe 

juniper takes over the grasslands.

Just as farmers add fertilizers to 

garden soils, fire releases nitrogen 

and phosphorus in plants back into 

the earth. The blackened surface 

warms the soils and aids this natural 

fertilization. That’s why you often 

see the first lush plants of the new 

growing season in recently burned 

areas.

For much of the past century, 

managers attempted to put out fires 

to protect lands and people. But they 

also suppressed the natural role of 

fire in keeping habitats healthy and 

diverse. Without regular burns, more 

fuels build up so that when wildland 

fires do start, they have a higher 

likelihood of burning out of control

Today, the Balcones team of fire 

experts use prescribed burning to 

improve wildlife habitats and reduce 

the risk of catastrophic fires. They 

are returning the process of fire as 

a natural tool to restore grasslands, 

savannahs and woodlands that harbor 

a tapestry of bird and animal life.
Wildfires often 

burn with greater 

severity on lands 

that have not 

benefited from 

prescribed burns 

or removal of 

hazardous fuels.

FWS photograph

Two endangered migratory songbirds 

fly north each spring to nest within 

Balcones Canyonlands NWR, 

established in 1992 to preserve and 

maintain their dwindling habitat, 

along with many species of concern 

in the Texas Hill Country. To bring 

back the black-capped vireo and 

golden-cheeked warbler from the 

brink of extinction will take restoring 

their strikingly different nesting 

habitats with the aid of prescribed 

fire. The vireo selects shrublands 

of varied heights that extend to 

ground level and are found in patches 

within grasslands and tend to avoid 

areas with higher juniper densities. 

The golden-cheeked warbler nests 

in dense forests and woodlands 

containing Ashe juniper and a variety 

of oak and other deciduous trees.

“We were, in fact, just entering a vast 

region, of which live-oak prairies are 

the characteristic.” Olmstead (1857).

Fire managers study historical 

conditions to learn about the fire 

process of the past. They know 

that in addition to lightning-caused 

burns, Native Americans and even 

early settlers ignited some fires 

to invigorate plant growth. A few 

historical records give clues to how 

the refuge lands once appeared. One 

author noted the “timber is much 

interrupted by open, grassy uplands” 

(Bray, 1904). Another described the 

large grasslands with woodlands on 

“rough slopes and hillsides, breaks of 

streams and summits of plateaus and 

mesas” (Foster, 1917).

What’s at Stake?

Learning from 

Historic Records
A firefighter 

ignites a 

prescribed 

burn that takes 

place only after 

considerable 

planning.

FWS photograph

The lands before 1850 appeared to 

be more open than found today, with 

grasslands punctuated by “cedar 

brakes, oak savannahs, oak thickets 

and mesquite savannahs” (Smeins, 

1980). From 1850 to the present, fires 

have been greatly diminished on the 

prairies and woody plants have spread 

into the grasslands.

Despite efforts to control its spread, 

fire has never left this landscape. A 

wildfire in 1879 burned thousands 

of square miles. The Texas High 

Plains fires blanketed more than 

one million acres in November of 

1906. Today, even with modern 

organized fire suppression and a 

landscape fragmented by roads and 

developments, the potential for large 

fires exists.

Rainfall and droughts have long 

influenced fire patterns that in the 

past burned at different intensities 

and created a mosaic of habitats. 

The refuge receives about 32 inches 

of rain annually with peaks in May 

and October. August is normally the 

driest and hottest month. Spring 

rainfall nourishes grasses and forbs to 

become the fine fuels of late summer 

that carry surface fires across prairies 

and savannahs. During extended dry 

periods and droughts, the woodland 

vegetation also becomes desiccated 

and susceptible to wildfires.

The Climate 

Connection
Prairie grasslands historically burned frequently—a 

natural ecological process.

FWS Photograph

Fire managers and ecologists decide 

how often lands should burn to 

restore natural conditions. If an area 

burns twice in less than seven years, 

those fires could significantly reduce 

many wood species that are less 

adapted to fire. An interval of 10 to 20 

years between fires would maintain 

grassland or savannahs without 

eliminating most woody plants. Longer 

intervals could generate massive fuel 

loading and stand-replacing fires 

during droughts. All of these scenarios 

would maintain the landscape diversity 

in a grassland/woodland mosaic.

Fire management goals are threepronged: to revive the health of 

grasslands and savannahs; to restore 

forests, woodlands and shrublands; 

and to enhance wildlife habitat 

diversity across the landscape—with 

special attention on the black-capped 

vireo and golden-cheeked warbler.

The Balcones fire management team 

includes experts in both prescribed 

and wildland fires. They develop burn 

plans to retore the role of fire for 

habitat diversity. They also protect 

wildland urban interface communities 

from the threats of fire by reducing 

fuels. The team even travels to other 

refuges to help them with prescribed 

burns.

How long 

between fires?

Goals for Refuge 

Fire Management
Higher nighttime humidity helps 

extinguish many fires.

FWS Photograph

To visit a native prairie in this part of 

Texas is to step into a life-filled land 

where big bluestem and Indian grass 

ripple in the winds, where foxglove 

and Indian paintbrush bloom and 

songbirds take shelter. Most of the 

native grasslands and savannahs 

have vanished after years of plowing 

and intense grazing. However, the 

refuge grasslands hold the promise of 

a native prairie’s return. Prescribed 

fires are promoting native plant 

restoration, and the control of 

invasive plants like second-growth 

juniper, prickly pear and false willow, 

as well as of exotic plants like the 

King Ranch bluestem.

Beyond the open lands lie a myriad 

of woodlands. Juniper-oak forests 

line the canyons, valleys and 

drainages. Shin oak woodlands grow 

in the uplands. Oak-elm-juniper 

savannahs extend on both uplands 

and broad floodplains. In some 

places, Ashe junipers are taking over 

former grasslands, because of fire 

suppression and improper livestock 

management. In these habitats, the 

role of prescribed fire varies. For 

example, fire managers strive to 

prevent catastrophic fires in juniperoak forests, while applying fire as a 

tool to thin shin oak woodlands.

Reviving 

Grasslands and 

Savannahs

Restoring Forests, 

Woodlands and 

Shrublands
Prescribed burns typically use 

natural and human-made fuel breaks 

to contain the fire.

FWS Photograph

Black-capped 

vireos nest in 

shrublands that 

require periodic 

fire to maintain 

them.

FWS Photograph

The black-capped vireo weaves a 

cup nest in the fork of a low branch 

in shin oak or sumac. Managers use 

prescribed fire to maintain, enhance 

or create shrublands of the suitable 

height for preferred nesting sites. 

They also mechanically remove the 

invading Ashe juniper. Their goal is to 

assure the vireo has plentiful stands 

of open oak brush (also called patches, 

mottes or “shinneries”) between one 

and about nine feet tall for nesting 

and raising young.

Fires that burn in vireo habitat affect 

the trees and plants differently, 

depending on the intensity. A more 

severe fire destroys all above ground 

vegetation, which leads to resprouting 

of shrublands—setting back 

succession. A lighter fire may burn 

the smallest live branches of trees and 

consume the dead branches closest to 

the ground.

Hope for the 

Black-capped 

Vireo

How Fire Shapes 

Vireo Habitat
Golden-cheeked warblers nest in 

dense forests that can be destroyed by 

wildfire. Managers construct shaded 

fuel breaks around nesting habitats 

to reduce wildfire threat.

FWS Photograph

Fire managers avoid nesting season 

when they prescribe burns. To 

maintain habitat, they set light or 

“cool” fires to penetrate part way into 

the oak-mottes. The flames leave the 

taller bushes and trees intact, remove 

understory and prevents to many Ashe 

junipers from growing in the area. To 

return the oak shrublands to an earlier 

succession stage, managers apply 

fire and mechanically remove taller 

trees that survive the burn. When the 

vireos arrive in spring from a winter 

in Mexico, they find their nesting 

places more inviting than ever. The 

refuge then helps the birds further by 

trapping brown-headed cowbirds that 

prey on vireos by laying their eggs in 

vireo nests.

Nesting only in the mature juniperoak woodlands of Texas, the 

endangered golden-cheeked warbler 

finds some of its best remaining 

habitat within Balcones Canyonlands 

NWR. This songbird seeks forests 

with an unbroken canopy of trees that 

are relatively tall with a high density 

of oaks—found mostly on steep slopes, 

riparian areas and other wetter sites. 

Hope for the 

Golden-Cheeked 

Warbler
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Marble Falls

Georgetown

Liberty Hill

Bertram

Burnet

BALCONES CANYONLANDS

NATIONAL WILDLIFE REFUGE

Austin, TX

Marble Falls

Georgetown

Liberty Hill

Bertram

Burnet

BALCONES CANYONLANDS

NATIONAL WILDLIFE REFUGE

Colorado River

Enlarged Area

The warbler also needs the shedding 

bark of Ashe juniper to weave its nest. 

Junipers must be at least 20 years 

old before they start shedding back 

and shed more bark which is more 

available nesting material.

In contrast to the vireo, the goldencheeked warbler inhabits areas 

where fire was historically less of an 

influence. Rocky escarpments and 

limestone karst formations serve as 

natural barriers to fire, protecting 

some of the denser, older forests. 

However, wildland fire has the 

potential to destroy prime habitats 

on the refuge. Here, managers create 

shaded fuel breaks surrounding 

known nesting warbler areas that 

maintain some of the important 

habitat elements. They also remove 

brush-clearing piles, fence posts and 

other potential fuels.

Managers apply prescribed fire to 

enhance low quality woodlands for 

future nesting. The fires help recycle 

nutrients, thin juniper saplings and 

stimulate hardwoods to sprout and 

grow more vigorously. They also thin 

stands of young junipers around the 

mature hardwoods to give seedlings a 

better chance for survival.

Keeping Fire Out 

of Prime Warbler 

Habitat

Prescribing 

Fire for Future 

Warbler Habitat
Prescribed fire is an evolving science 

with many partners. Balcones 

Canyonlands NWR is teaming up 

with the National Park Service, Lady 

Bird Johnson Wildflower Center, 

Texas State University, Baylor 

University, and the Texas Agricultural 

Experiment Station to test prescribed 

fire methods aimed at restoring native 

grasses and forbs. Located at the

San Marcos National Fish Hatchery 

and Technology Center, the project 

features test plots on the facility’s 

small tract of blackland prairie. 

There, the partners compare burning, 

mowing, and herbicides on the 

eradication of invasive King Ranch 

bluestem. Researchers also conduct 

summer prescribed burns for prairie 

maintenance and restoration.

For current fire danger levels and 

burn bans, visit the Balcones Fire 

Management Program web site at: 

www.fws.gov/southwest/refuges/

texas/balcones/firemanagement.html

You can contact the Balcones 

Canyonlands NWR Fire Management 

Program or the Refuge Manager at the 

address on the brochure’s back cover.

For More 

Information

Research

Partners
Literature Cited Armstrong, W.E. 1980. 

Impact of prescribed burning 

on wildlife. In L.D. White (ed.), 

Prescribed range burning on the 

Edwards Plateau of Texas, PP. 22-

26. Texas Agric. Ext. Serv., College 

Station

Box, T.W., J. Powell, and D.L. 

Drawe. 1967. Influence of Fire on 

South Texas Chaparral Communities. 

Ecology. Vol. 148, page 955-961

Bray, W. L. 1904. The timber 

of the Edwards Plateau of Texas: its 

relation to climate, water supply and 

soil. U.S. Dep. Agr., Bur. For. Bull. No. 

49. 30 p.

Foster, J. H. 1917. The spread 

of timbered areas in central Texas. J. 

For. 15:442-445.

Olmsted, F. L. 1857. A Journey 

Through Texas or, a Saddle-Trip on 

the Southwestern Frontier. Univ. Tex. 

Press, Austin. 516 p.

Smeins, F. 1980. Natural role 

of fire on the Edwards Plateau, Pages 

4-16, In Prescribed Range Burning on 

the Edwards Plateau Texas, Larry D. 

White (Ed) Proceedings of a Symposium 

held October 23, at Junction, Texas.

Wright, H. A. and A. W. 

Bailey. 1982. Fire Ecology, United 

States and Southern Canada. Wiley 

and Sons Press, New York. 501 pp.
Balcones Canyonlands National Wildlife Refuge

24518 FM 1431

Box 1

Marble Falls, TX 78654

512/339-9432

512/267-6530 FAX

Texas State Relay Service

1 800/735-2989

U.S. Fish and Wildlife Service

http://www.fws.gov/southwest

For Refuge Information

1 800/344-WILD

Prescribed burn at Balcones Canyonlands NWR

FWS Photograph

September 2008