Endangered Birds of the BCP

Balcones Canyonlands Biology

Golden-cheeked Warbler

Black-capped Vireo

The Birds

Photo by John Ingram

Listed as endangered in 1990

Listed as endangered in 1987

Habitat for these two endangered birds

accounts for almost all of the 30,000+ acres on

maps of the Balcones Canyonlands Preserve

Presented by Bill Reiner, biologist

City of Austin Wildland Conservation Div.

What are Golden-cheeked Warblers?

Photos by John Ingram

about 5 inches long

male

female

Small forest-dwelling songbirds

Eat insects and spiders they find among the leaves

Raise young only where the female can find bark from mature Ashe Juniper trees to build her nest

Heard more easily than seen, since they live mostly in the treetops

They winter in pine-oak woodlands in the highlands of southern Mexico and central America

Where do Golden-cheeked Warblers Live?

These birds breed only in the juniper-oak woodlands of central Texas -- so they are all native Texans

They migrate along the Sierra Madre Oriental in coniferous forest


The Golden-cheeked Warbler is a forest-interior species.

Golden-cheeked Warbler habitat: tall trees, with high percent canopy cover.

Golden-cheeked Warbler habitat: dense cedar (can be hard to walk through).

They need mature Ashe Junipers – also known as cedars – for

nesting and food (insects and spiders).


Golden-cheeked Warblers nest exclusively in woodlands of

mature Ashe Juniper and hardwoods, especially oaks.

Their nesting season runs from early March through July.

Golden-cheeked Warblers nest exclusively in woodlands of

mature Ashe Juniper and hardwoods, especially oaks.

Photo by Jim & Lynne Weber

Their nesting season runs from early March through July.

The nest is a small cup made

mostly of long strips of mature

Ashe Juniper bark.

Photo by Amanda Aurora


(GCWA) Nest A female builds her nest in the fork of a juniper or

hardwood, often near the trunk.

Height varies, but it is usually

placed in the upper two-thirds

of the tree, and very well

concealed.

Photo by Misa Soliz

Newly-fledged Golden-cheeked Warbler chick,

being fed by its mother Film clip: Bill Reiner

Hatch-year (“teenage”) Golden-cheeked Warblers

bathing and drinking from a puddle on a Preserve road

Film clip: Bill Reiner

How are the Golden-cheeked Warblers doing?

• Endangered status is based upon

loss of habitat, which continues.

• Endangered Species Act has led to

protection of some habitat, but

permitted destruction as compromise.

• Balcones Canyonlands Conservation

Plan allows for up to 70% of habitat in

Travis County to be destroyed.

• Recent estimate: 100,000 acres of habitat

(range-wide) were lost in the decade after

the warblers were protected…

…and the rate of loss has has continued

since then…

…so warbler populations are almost

certainly still declining.

How are the Golden-cheeked Warblers doing?

• Re-growing suitable old-growth habitat

takes several decades to a century or

more.

• If ESA protections remain in place, the

best habitat will be saved, and loss will

be minimized.

• With continued loss of habitat, the

warbler population is almost certainly

still declining,…

… though it is difficult to estimate

population with so many birds on

private lands.

• Ashe Juniper grows very slowly –

estimates from long-term studies found

1 inch diameter per decade.

• Many landowners wrongly believe

cedar is not native, and a weed to be

eradicated.

• So habitat loss will likely accelerate

if ESA restrictions are removed.

Major Threats to Warblers and Vireos:

Habitat Loss and Fragmentation

Habitat Fragmentation

Source: http://www.realinstitutoelcano.org/documentos/100.asp

Edge Effects

Predators found in higher

numbers along edges:

Rat snakes

Jays, crows

Fox squirrels

Fire ants

Brown-headed cowbirds

Raccoons, ringtails, opossums

Roadrunners

Eastern Screech-Owls Photo by Bill Reiner

Edge = meeting between forest/shrubland and open/suburban areas

Very different conditions than in the interior:

More wind and light, higher temperature – may lead to dryer environment

Competing invasive plant and animal species

Increased numbers of predators/parasites

Texas Rat Snakes

Known predators of nests and young:

Eastern Fox Squirrels

Raccoons

Jays

Red Imported Fire Ants

female Brown-headed Cowbird

male Brown-headed Cowbird

Brown-headed Cowbird

Major Threats to Warblers and Vireos:

Habitat Loss and Fragmentation

Photo by Greg Lasley

How you can help

Plan maintenance work for fall & winter

Avoid critical nesting season

(March 1-Sept 1)

Where possible, avoid creating

gaps in the tree cover

Prune only as necessary

Prevent spread of oak wilt

Submit a wildfire prevention plan

Control erosion & sedimentation

Protect native plants, and remove

non-native species

Avoid driving dirt roads after rain

How you can help

Photo by Carl Schattenberg

…especially over roads


(March 1-Sept 1)








non-native species


How you can help


Photo by Bill Reiner Leave trees in canyons

Top trees instead of removing them


(March 1-Sept 1)








non-native species


How you can help



(March 1-Sept 1)








non-native species


How you can help


(March 1-Sept 1)








non-native species


How you can help


(March 1-Sept 1)








non-native species


How you can help Agarita

Flameleaf Sumac


(March 1-Sept 1)








non-native species


Virginia Wildrye Waxleaf Ligustrum

Mexican-Buckeye

Inland Sea-Oats

How you can help


(March 1-Sept 1)








non-native species


Black-capped Vireo (Vireo atricapilla)

about 4.5 inches long

Males have solid black caps Vireo bills are stout

with a hooked tip

Photo by Billy Simper

Some males

may have a

grayish nape

…and they know

how to use them!

Photo by Billy Simper

Females have a slate-

gray crown, but

black near the eyes

Both sexes have white “spectacles” and

reddish eyes

Green back

= “Vireo”

Photo by Gil Eckrich

• The birds mate, nest,

and raise young in

Oklahoma, Texas, and

Coahuila.

Where do Black-capped Vireos Live?

• Like the warblers, they

must migrate south to

find enough food when

cold weather reduces the

numbers of insects.

• They spend the winter

on the Pacific coast of

Mexico.

• The first birds return

to Texas in mid-March,

and by April are nesting.

Vireos need a mix of open areas (grassy or rocky)

with broad-leaved shrubs of varying heights

Black-capped Vireo habitat

Very different from


habitat, it is transitional

between grassland and

mature woodland

The shrub cover is generally 30% to

60%, and less than 10 feet tall

Some taller trees are useful,

especially for song perches


Scrubby oaks

(“shinnery”)

provide ideal

cover for nests Important characteristic:

a “skirt” of foliage, extending

to the ground, which conceals

the low-hanging nest

The kind of shrub is less

critical than its structure


Black-capped Vireo nest

Usually built in a broad-leaved shrub

1.5 to 6 feet above the ground

Hangs from a terminal or sub-terminal

branch fork, screened by low foliage

Black-capped Vireos lose habitat

through natural succession from

shrub land to forest

Succession: Shrubs to Trees

Photo by John Ingram Photo by John Ingram

When the thickets become too dense

and tall, the vireos disappear.

It may be necessary to thin the trees to restore

the open shrubland.

Shin Oaks and Live Oaks will re-sprout from

the roots, forming shinnery again.

Setting Back Succession

Vireos will often return to the site

when it becomes suitable.


Our permit mandates 2,000

acres of BCVI habitat

Less than 400 acres are now

occupied on all BCP tracts

So we need to expand habitat for

vireos on the Preserve, but how

to do that is a challenge.

In particular, we do not want to

sacrifice mature woodlands that

are Golden-cheeked Warbler

habitat to benefit the vireos.

Black-capped Vireos

on the Preserve Currently, the largest BCVI

colony within the Preserve is

on Travis County property.

Austin

Bee Cave

Lakeway

Lake

Travis

US 183

Loop 360

However, some areas of the

Preserve have marginal warbler

habitat. Preserve managers have

attempted to create suitable

vireo habitat in those areas.

Creating habitat for Black-capped Vireos Maintaining existing vireo habitat is one

thing. Creating new habitat is another.

Unless the right kinds of plants are

already present, removing the existing

trees only results in a grassland (at best).

Preserve managers have tried planting seeds and seedlings of shrub-forming species.

So far, in open areas without irrigation, those attempts have failed.

Thank you for your help!


Black-capped Vireo


Environment

Endangered Birds of the BCP