A N T H O N Y K . H E N E H A N 1 , F I D E LH E R N Á N D E Z 1 , E R I C D . G R A H M A N N 1 , T I M O T H Y E . F U L B R I G H T 1 , A N D R E W N . T R I 3 , D A V I D B . W E S T E R 1 , A N D M I C H A E L H E H M A N 2

Wintering and Breeding Bird Population Response to On-going Large-scale Grassland Restoration

1 C A E S A R K L E B E R G W I L D L I F E R E S E A R C H I N S T I T U T E , T E X A SA & M U N I V E R S I T Y - K I N G S V I L L E , K I N G S V I L L E T X 7 8 3 6 3

2 H I X O N R A N C H , C O T U L L A T X 7 8 0 1 4

3 M I N N E S O T A D N R , S T . P A U L M N 5 5 1 5 5

Non-native grasses

� Mixed effects on birds:

� Vegetation structure is more important than species for wintering grassland birds1

� For some species of grassland bird, non-native grasses can substitute for nesting cover when native grasses are lacking2

Photo: Anthony Henehan

� Spread throughout the United States

1Block and Morrison 2010, Macías-Duerte and Panjabi 2013, Ruth et al. 20142 Jones and Bock 2005

Buffelgrass

� Buffelgrass (Pennisetum ciliare) is a bunch-forming grass native to Africa

� Creates dense monotypic stands, reducing diversity and structure of grasslands

� Presently found throughout the southwestern United States limited to areas without freezing

Photos: Matt Wojda

Buffelgrass: South Texas “Wondergrass”

� Planted in southern Texas in the early 1900s. Failed to establish until the 1940s

� Hailed as a solution to drought-related forage problems

� Increased stocking rates from 12 ha/animal unit to 4 ha/animal unit (Hanselka 1988)

Photos: Matt Wojda

Buffelgrass and Birds

� Little is known regarding effects of buffelgrass on birds

� Flanders et al. (2006) found decreased densities of birds on buffelgrass-dominated grasslands

� Dealt only with breeding birds; wintering bird response to buffelgrass unknown

Photos: Anthony Henehan

Habitat Restoration

� Prior research on grassland restoration dealt with small-scale (<5 ha) studies

� Large-scale (>50 ha) restoration projects may offer insight into population-wide responses of grassland birds to these efforts

� Our study: 118 ha restoration project

Photo: Matt Wojda

Restoration Timeline

Photo: Matt Wojda

2013 2014 2015 2016 2017

Pre-restoration Restoration Activities Post-restoration monitoring

Winter Bird

Breeding Bird

Hypotheses and Objective

� H1: Buffelgrass decreases the density of wintering and breeding grassland birds

� H2: Maintaining brush mottes will maintain an avian presence during restoration

� Estimate density of these groups and compare among study areas over time

Photos: Anthony Henehan

Study Areas

NA

RE

NN

3 Study Areas in La Salle County, TX• Non-native Area (109-ha): dominated by buffelgrass and mesquite (Prosopsis

glandulosa)• Native Area (117-ha): thorn-scrub dominated by species such as granjeno (Celtis

ehrenbergiana) and huisache (Acacia farnesiana)• Restoration Area (118-ha): pre-restoration similar to non-native area. During

restoration, site devoid of grass. Some mesquite mottes left

Restoration Area Pre- and During Restoration

Pre-restoration During restoration

Study Areas

Non-native Area Native Area

Bird Survey Methods

� Point-transect distance sampling

� Winter (Dec–Jan 2013–2014)

� Summer (Jun–Jul 2014–2015)

� Start at sunrise, end 3 hours after sunrise

� 100-m radius, 3 minutes of silence, 5 minutes of surveying

� Record distance to every bird from point with laser rangefinder

� Non-native control: 15 points

� Native control: 23 points

� Restoration: 23 points

Data Analysis

� Analyzed data in Distance 6.2

� 2 Analyses:

� Study area and year

� Grassland and Shrubland Birds

� Tested 6 different models for each dataset

� Chose best model based on AIC values

� Bootstrapped 999 iterations

� Reporting bootstrapped densities with 95% CI

Rainfall

4.83

11.38

7.79

17.79

0

2

4

6

8

10

12

14

16

18

20

Winter Summer

Ra

infa

ll (

cm)

Season

Total Rainfall

2013/2014

2014/2015

Winter Bird Richness

18 18

24

16

19

10

0

5

10

15

20

25

30

Non-native Native Restoration

Nu

mb

er

of

Sp

eci

es

Study Area

Winter Bird Richness

2013

2014

Winter Total Density

Reporting bootstrapped densities with 95% CI

15.93

7.12

19.7

13.07 12.56

4.08

0

5

10

15

20

25

30

35

NN NA RE

Bir

ds

pe

r h

a

Study Area

Total Winter Bird Densities

Pre-restoration

During Restoration

Winter Group Densities

Reporting bootstrapped densities with 95% CI

15.73

3.38

20.04

11.9

2.49 2.190

5

10

15

20

25

30

35

NN NA RE

Bir

ds

pe

ha

Study Area

Winter Grassland Bird Densities

Pre-restoration

During Restoration

0.9

6.07

1.351.36

10.53

2.13

0

5

10

15

NN NA RE

Bir

ds

pe

r h

a

Study Area

Winter Shrubland Bird Densities

Pre-restoration

During Restoration

Summer Bird Richness

16

1819

13

20

7

0

5

10

15

20

25

NN NA RE

Nu

mb

er

of

Sp

eci

es

Study Area

Summer Bird Richness During Restoration

2014

2015

Summer Total Density

Reporting bootstrapped densities with 95% CI

10.48

18.63

5.98

9.01

12.4

2.72

0

5

10

15

20

25

30

NN NA RE*

Bir

ds

pe

r h

a

Study Area

Total Summer Bird Densities During Restoration

2014

2015

*n < 15

Summer Group Densities

Reporting bootstrapped densities with 95% CI

2.611.37 1.17

7.01

1.43

0

2

4

6

8

10

12

14

NN NA RE*

Bir

ds

pe

r h

a

Study Area

Summer Grassland Bird Densities During Restoration

2014

2015

7.96

17.15

4.973.94

11.38

0

5

10

15

20

25

NN NA RE

Bir

ds

pe

r h

a

Study Area

Summer Shrubland Bird Densities During Restoration

2014

2015

*n < 15

Discussion- Restoration Area

� Large decrease in wintering birds on restoration area to be expected� Hope to document an increase in wintering and breeding bird densities

post-restoration

� Still maintained an avian presence during winter

� Breeding birds appear to be mainly shrubland birds

� Even during heavy rainfall year (2015), did not obtain sufficient observations to estimate density

Photos: Anthony Henehan

Other insights

� Non-native grasslands utilized heavily by grassland birds in winter

� Depending on rainfall, non-native grassland breeding bird assemblage changes from shrubland to grassland birds � Mostly Dickcissel (Rappole and Blacklock 1985)

Photos: Anthony Henehan

Management Implications

� Brush mottes appear to act as refugia for maintaining an avian presence during winter

� Not as effective for breeding birds

� Buffelgrass stands may not be as adverse environments as initially thought for wintering birds

Literature Cited

� Block, G., and M. L. Morrison. 2010. Large-scale effects on bird assemblages in desert grasslands. Western North American Naturalist 70:19–25.

� Flanders, A. A., W. P. Kuvlesky, Jr., D. C. Ruthven III, R. E. Zaiglin, R. L. Bingham, T. E. Fulbright, F. Hernández, and L. A. Brennan. 2006. Effects of invasive exotic grasses on South Texas rangeland breeding birds. The Auk 123:171–182.

� Hanselka C. W. 1988. Buffelgrass: South Texas wonder grass. Rangelands 10:279–281.

� Jones, Z. F., and C. E. Bock. 2005. The Botteri’s Sparrow and exotic Arizona grasslands: An ecological trap or habitat regained? The Condor 107:731-741.

� Macías-Duerte, A., and A. O. Panjabi. 2013. Association of habitat characteristics with winter survival of a declining grassland bird in Chihuahuan desert grasslands of Mexico. The Auk 130:141–149.

� Rappole, J. H., and G. W. Blacklock. 1985. Birds of the Texas Coastal Bend. Texas A&M University, College Station, Texas, USA.

� Ruth, J. M., T. R. Stanley, and C. E. Gordon. 2014. Associations of wintering birds with habitat in semidesert and plains grasslands in Arizona. The Southwestern Naturalist 59:199–211.

� Fidel Hernández� Timothy Fulbright� Eric Grahmann� David Wester� Andrew Tri� John Edwards� Michael Hehman� Danielle Belleny� Matt Wojda� Monika Burchette� Andrea Bruno

� The Hixon Ranch

� Tim and Karen Hixon

� Rene Barrientos

� Coastal Bend Audubon Society

� South Texas Quail Coalition

� Texas Parks & Wildlife

� Exxon Mobile

Contributors

Questions