BURROWING OWL NEST SITE USE AND PRODUCTIVITY ON ...

BURROWING OWL NEST SITE USE AND PRODUCTIVITY

ON PRAIRIE DOG COLONIES IN THE SOUTHERN

HIGH PLAINS OF TEXAS

by

ANDREW TEASCHNER, B.S.

A THESIS

IN

WILDLIFE SCIENCE

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

Approved

Mark C. Wallace Chairperson of the Committee

Clint William Boal

Nancy E. McIntyre

James D. Ray

Accepted

John Borrelli Dean of the Graduate School

August, 2005

ACKNOWLEDGEMENTS

Funding for this project was provided by the United States Department of

Energy/National Nuclear Security Administration in cooperation with BWXT Pantex,

L.L.C., Texas Tech University, United States Geological Survey - Texas Cooperative

Fisheries and Wildlife Research Unit, and Texas Parks and Wildlife Department. I would

like to thank Dr. Mark Wallace for his encouragement, guidance and support throughout

this project. I would like to thank Dr. Clint Boal for his support and guidance, especially

in the trapping and banding methods for birds of prey. I thank Jim Ray, Monty

Schoenhals and Mike Keck for their assistance in field work and coordination on the

Pantex Plant. I also thank all of the private landowners in Carson and Lubbock Counties

who allowed me access to their property for the purposes of this project.

I am indebted to everyone who assisted me in collecting data in the field: Cole

Baack, Blake Beall, Lisa Belmonte, Tracy Boal, David Butler, Lawson Dennis, Matthew

Giovanni, Carey Haralson, Nicole Jaurequi, Tiffany Lyon, Alison Pruett, Ryan Stout,

Chris Taylor, Lindi Van Heuklon, and Ryan Ward. I would like to thank my fellow

graduate students for their support and advice throughout the project. Finally, I would

like to thank my family who have supported my education and interest from the

beginning.

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TABLE OF CONTENTS

ACKNOWLEDGMENTS………………………………………………..……………..ii

LIST OF TABLES……………………………………………………………………...iv

LIST OF FIGURES……………………………………………………………………..v

CHAPTER

I. GENERAL INTRODUCTION………………………………………… 1

II. BURROWING OWL NEST SITE USE AND PRODUCTIVITY IN THE SOUTHERN HIGH PLAINS OF TEXAS.…………………... 4

Abstract…………………………………………….…………... 4 Introduction…………………………………………………….. 5 Study Area.………………………..…………………………… 6 Methods…………………………………………….………….. 7 Results…………………………………………………………. 11 Discussion………………………………………….…………... 15 Management Implications………………………….…………... 19 Literature Cited…………………………………….……………21

APPENDICES

A. BURROWING OWL TRAPPING DATA…………………………….. 39

B. VEGETATION TRANSECT DATA………………………………….. 52

C. COLONY MAPS………………………………………………………. 55

iii

LIST OF TABLES

2.1 Study sites chosen and data known prior to 2003 field season...………………. 28

2.2 Burrowing owls marked and seen by season combined for all sites.…………...29

2.3 Burrowing owl nesting and productivity data given by site for Lubbock and Carson County, Texas in 2003 and 2004………………………....30

2.4 Number of prairie dogs estimated and holes marked by site for Lubbock and Carson Counties, Texas in 2004………………………………….31

2.5 Number of burrowing owl pairs per buffer area by site for Lubbock and Carson County, Texas in 2003 and 2004…………………………32

iv

LIST OF FIGURES

2.1 The maximum number of burrowing owls seen on prairie dog colonies correlated to prairie dog colony size for a 12 county area searched for a

prairie dog colony study in the Texas Panhandle……………………………… 34 2.2 The number of burrowing owls caught by trap type and season across

all sites in Lubbock and Carson Counties, Texas in 2003 and 2004…….….…. 35 2.3 Number of burrowing owls seen in 2003 and 2004, with and without

bands for the 6 study sites in Lubbock and Carson Counties, Texas………….. 36 2.4 The number of burrowing owl pairs recorded in relation to prairie dog colony area in hectares for the 6 study sites in Lubbock and Carson Counties, Texas for 2003 and 2004……………………………………………. 37 2.5 The number of burrowing owl pairs recorded in relation to the number

of prairie dog holes marked in 2004 for the 6 study sites in Lubbock and Carson Counties, Texas………………………………………………………... 38

v

CHAPTER I

GENERAL INTRODUCTION

Western burrowing owls (Athene cunicularia hypugaea) are widely distributed

across the western portion of North America and can be found from deserts to

agricultural areas (Haug et al. 1993). Despite the wide distribution of this particular

species, Desmond et al. (2000), Korfanta et al. (2001), and Murphy et al. (2001) have

shown declines in the range and numbers of burrowing owls across the western U.S. and

Canada. Habitat destruction and land conversion are major causes for declines (Korfanta

et al. 2001, Martell et al. 2001, Murphy et al. 2001, Sheffield and Howery 2001).

Burrowing owls are considered a U.S. Fish and Wildlife Service regional conservation

priority (USFWS 2001).

In the Texas Panhandle, little research has been done on burrowing owls.

McIntyre (2004) indicated a long-term decline since the 1940’s of wintering owls

recorded in Christmas Bird Counts for this area, whereas Breeding Bird Survey data

suggested that summer burrowing owl populations may have remained stable since the

1960’s. Surveys of prairie dog colonies across 12 counties in the Southern High Plains of

Texas (Pruett 2004) showed that burrowing owl numbers were correlated to prairie dog

colony size. However, colony size explained very little of the up to 10-fold variation in

owl numbers that occurred over small colony sizes. This study was developed to assess

the use of prairie dog colonies as habitat by western burrowing owls (Athene cunicularia

hypugaea) in the Texas Panhandle. We wondered what factors might be responsible for

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some small prairie dog colonies having large numbers of owls while others had few.

While a potentially large number of variables could be involved, prairie dog density,

number of holes, vegetative composition or structure, and relative prey abundance were

measurable variables that we suspected were important.

The results of this research are presented in Chapter II. Chapter II assesses

burrowing owl presence on prairie dog colonies and related prairie dog colony parameters

to burrowing owl numbers and productivity and is formatted for submission to the

Wildlife Society Bulletin separately.

2

CHAPTER II

BURROWING OWL NEST SITE USE AND PRODUCTIVITY IN THE SOUTHERN

HIGH PLAINS OF TEXAS

3

6/9/2005

Andrew P. Teaschner Department of Range, Wildlife, and Fisheries Management Texas Tech University Lubbock, TX 79409 806-742-1981; E-mail: [email protected] RH: Burrowing Owl Nesting Southern High Plains • Teaschner et al.

Burrowing Owl Nest Site Use and Productivity in the Southern High Plains of Texas.

Andrew P. Teaschner, Department of Range, Wildlife, and Fisheries Management, P. O.

Box 42125, Texas Tech University, Lubbock, TX 79409, USA.

Mark C. Wallace, Department of Range, Wildlife, and Fisheries Management, P. O.

Box 42125, Texas Tech University, Lubbock, TX 79409, USA.

Clint W. Boal, Texas Cooperative Fish and Wildlife Research Unit, 218 Agriculture

Science, Texas Tech University, Lubbock TX 79409, USA.

Nancy E. McIntyre, Department of Biological Sciences, P. O. Box 43131, Texas Tech

University, Lubbock, TX 79409, USA.

James D. Ray, BWXT Pantex LLC, Pantex Plant, Bldg. T-9061, Amarillo, TX 79120,

USA.

Monty Schoenhals, BWXT Pantex LLC, Pantex Plant, Bldg. T-9061, Amarillo, TX

79120, USA.

Abstract

Large numbers of burrowing owls nest in the Texas Panhandle, yet very little is

known of their breeding ecology in the region. For this study we measured abundance of

4

burrowing owls and attempted to assess the number of resident verses migrant burrowing

owls through color banding and the monitoring of marked individuals, at a sample of

study areas in the Texas Panhandle. Burrowing owl productivity and prairie dog colony

parameters that could influence burrowing owl nest selection and success were also

measured. The majority of burrowing owls in our area are breeding season migrants.

Noose carpet and Bal-Chatri traps were the most effective trapping methods during the

breeding season. Number of breeding burrowing owl pairs was positively correlated to

colony area (r2 = 0.5498, P = 0.0060), and to number of prairie dog holes in a colony (r2

= 0.7327, P = 0.0296). Our measures of vegetative composition and structure were not

related to burrowing owl numbers or productivity.

Introduction

Western burrowing owls (Athene cunicularia hypugaea) are widely distributed

across the western portion of North America and can be found from deserts to

agricultural areas (Haug et al. 1993). Despite the wide distribution of this species,

Desmond et al. (2000), Korfanta et al. (2001), and Murphy et al. (2001) have shown

declines in the range and numbers of burrowing owls across the western U.S. and

Canada. Habitat destruction and land conversion are major causes for declines (Korfanta

et al. 2001, Martell et al. 2001, Murphy et al. 2001, Sheffield and Howery 2001).

Burrowing owls are considered a U.S. Fish and Wildlife Service regional conservation

priority (USFWS 2001).

In the Texas Panhandle, little research has been done on burrowing owls.

McIntyre (2004) indicated a long-term decline since the 1940’s of wintering owls

5

recorded in Christmas Bird Counts for this area, whereas Breeding Bird Survey data

suggested that summer burrowing owl populations may have remained stable since the

1960’s. Pruett (2004) recorded number of burrowing owls seen while surveying prairie

dogs in a 12 county area of the Southern High Plains of Texas. The number of

burrowing owls observed (Figure 2.1) was positively correlated (r2 = 0.0182, P = 0.0107)

to prairie dog colony size. However, there was >20-fold range in the number of owls

seen in smaller (2 to 20 ha) prairie dog colonies.

Information is lacking on all aspects of burrowing owl ecology that may be

unique to this area. Our objectives were to describe burrowing owl use of prairie dog

colonies and examine factors that might explain why some colonies are used more than

others. We were specifically interested in determining the relationship between numbers

of owls, prairie dog density, and colony size. We also examined related factors that could

affect burrowing owl use of prairie dog colonies, including relative prey abundance,

proximity to playas containing water, and vegetative structure associated with prairie dog

colonies.

Study area

We chose our study sites from a subset of sites surveyed for a companion study

on prairie dogs in relation to playas (Pruett 2004). We selected 3 sites on the Pantex

Plant in Carson County, TX, and 3 in the Lubbock area, Lubbock County, TX, for

burrowing owl trapping, banding, and observation. These sites were selected because we

knew, from previous surveys (McCaffrey 2001, Pruett 2004), that they provided nesting

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sites for burrowing owls and they represented prairie dog colony sizes 2.9 to 11.6 ha.

Study sites (Table 2.1) were chosen to have representative patterns of surrounding land

use and histories of on-site management activity. The Pantex Plant provided sites that

were relatively undisturbed (during our observation period) with a known history of

grazing and prairie dog control activities. Lubbock area sites provided agricultural sites

and abandoned areas within urbanizing landscapes.

Methods

We used Bal-Chatri traps, noose carpets (Mealy 1997, Millsap and Bear 1997),

walk-in traps (Botelho and Arrowood 1995, Banuelos 1997), and bow nets (Bloom 1987)

to trap burrowing owls. Captured owls were banded with one USFWS leg band and one

red alpha-numerically coded anodized aluminum band. We recorded captured

individuals as adult or juvenile based on plumage (Haug et al. 1993). To determine

whether individuals were migrants or residents, we attempted to relocate banded owls

weekly. We monitored burrowing owls with spotting scopes and binoculars from parked

vehicles, which we used as viewing blinds (Coulombe 1971). Walking through a prairie

dog colony to detect burrowing owls or observing a colony for ≥30mins from a vehicle

blind during any one day was defined as a search day for that site. Timing of migration

was assessed based on presence or absence of individually identifiable marked owls

during >3 monthly counts at each site. Identification of individual burrowing owls was

also used to determine individual nest sites, and between year area and pair fidelity.

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Nesting

Owls were not recorded as nesting pairs until we observed chicks at burrows.

Chicks have been recorded moving between nest burrows as young as 10 days old

(Henny and Blus 1981). Once a chick was observed above ground it was considered

“fledged.” Therefore, all pairs recorded as nesting were by definition successful nesters.

We recorded the number of burrowing owls, marked burrowing owls, nesting burrows

and maximum number of chicks seen per nest burrow (Martin 1973, Green and Anthony

1989, Desmond and Savidge 1996). We attempted to search all 6 main sites ≥1

time/week. We searched adjacent prairie dog colonies within 8 km of our 6 study sites,

opportunistically in an attempt to determine whether marked individuals moved between

prairie dog colonies or remained on the prairie dog colony on which they were marked.

To obtain relative measures of productivity, we monitored nesting burrows for 3

separate 10-minute periods within a 2-week period as nestlings began to emerge from

burrows (Gleason and Johnson 1985). We defined productivity as the maximum number

of young birds seen at any one period for each natal burrow.

We examined correlations between number of burrowing owl pairs and

productivity to prairie dog colony size, number of prairie dogs, and number of vacant

prairie dog holes. We determined perimeters of our study colonies by walking around the

exterior burrows with a handheld global positioning satellite (GPS) unit (Garmin model

12, Garmin Intenational Inc. Olathe, KS). The GPS track was then uploaded onto a

computer to determine colony area. Number of prairie dogs was estimated using 3 counts

following Pruett (2004). During 2004, we made a complete count of all holes on each of

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our sites. Location of each prairie dog hole at the 6 sites, including holes used as nesting

burrows by burrowing owls, was recorded using GPS. We derived an index of “vacant”

holes by dividing the number of holes counted at each site by the estimated (Pruett 2004)

number of prairie dogs present (Table 2.4). We reasoned that sites with a higher index

(more holes per prairie dog) should have more “vacant” holes available for burrowing

owls to use. If burrowing owls used parts of prairie dog colonies where holes were

more or less densely packed then the distance from nest burrows to holes should differ

from the distance between holes. We randomly selected an equal number of prairie dog

holes as there were burrowing owl nests on each site and compared distance from each

nesting burrow to its’ 5 closest prairie dog holes to the distance from the random holes to

their 5 closest prairie dog holes. We created 50-m buffers from prairie dog colony

centers using ArcView GIS and counted the number of owl nesting burrows per unit area.

Given the size of prairie dog colonies on our sites, all holes were within 3 of these 50-m

buffers from the colony center. We also compared the calculated distance from

burrowing owl nest burrows to the geographic center of the colony and to the nearest

colony edge.

Distance to playas containing water was used as an index of food availability,

since many amphibians and insects in this area use playas to complete their life cycle

(Anderson 1997). Local playas were identified from available GIS mapping (Fish et al.

1995, Pruett 2004). We checked for the presence of water during burrowing owl nesting

and recorded distances to nearest adjacent playas containing water to correlate distance to

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playas containing water to number of burrowing owl nests and nest success using

Pearson’s product moment correlation.

We assessed relative abundance of small mammals, another potential food source

for burrowing owls, by trapping on the 6 prairie dog colonies. Trapping grids consisting

of 100 Sherman live traps that were set for a period of 3 consecutive nights. All captured

mammals were identified to species and sex, weighed, measured, and marked for

identification upon recapture (Pruett 2004). Numbers of initial captures were compared

between sites for all species that are considered possible prey for burrowing owls to

assess relative abundance of foods in relation to burrowing owl nest density and success.

We also examined vegetative data to assess characteristics of burrowing owl

nesting sites and vegetative structure and composition. Two 25-m line intercept transects

were randomly placed in each prairie dog colony. Percent cover (intercept distance) of

vegetation along each transect was recorded by category: grass, forb, shrub, litter, bare

ground, or other (Bullock 1996). Visual obstruction was estimated using (n=6/transect)

Robel pole measures (Vermeire et al. 2002) taken at 5-m intervals along each 25-m

transect. We modified the lowest 2 decimeters of our pole marking off 2-cm intervals

with which to record heights of the commonly <1 decimeter tall vegetation on our sites.

We used Statistica (StatSoft, Inc. (2003). STATISTICA (data analysis software

system), version 6. www.statsoft.com) to calculate all statistical tests at the α = 0.05 level

of significance. All research was conducted following methods approved by the Texas

Tech animal care and use committee (protocol # 03014-02). Burrowing owl trapping and

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banding was conducted under the Federal Bird Marking and Salvage Permit (Permit #

22801-D).

Results

We captured burrowing owls (n=153; 137 adult, 16 juvenile) between January

2002 and July 2004 and banded them with USFWS No. 4 leg bands; n=130 of the 137

banded adults also received uniquely alpha-numeric coded red anodized aluminum leg

bands (Appendix A). Capture method success varied by season. Most owls (89%; 137 of

153) were captured during the summer breeding periods when Bal-Chatri and noose

carpet traps (87%; 119 of 137 total summer captures) were most successful (Figure 2.2).

Of the summer-banded owls, 14 (13 color banded adults and 1 juvenile) were captured

for a concurrent research project and were not monitored after capture for this project;

however, their trapping data are included in trap success and Appendix A. We baited

Bal-Chatri traps with domestic white mice (Mus musculus) and placed noose carpets

adjacent to burrow entrances occupied by a nesting pair of owls. Very few owls (n=7-18)

were observed on our 6 intensive sites during winter months. Therefore, we increased our

trapping and survey area by adding 3 sites on the Pantex Plant in Carson County during

winter 2004. Only 12% (n=16; 3 on the added sites) of all owls were captured during the

winter periods and most (81.3%; 13 of 16 captured) of these were captured with walk-in

traps placed over burrows that owls were observed entering.

We conducted searches (n=111) on our 6 intensive sites (mean + SE 3.5 ± 1.8

searches per month) per site between September 2003 and April 2005 and counted the

number of burrowing owls and marked burrowing owls observed. We attempted to assess

11

timing of seasonal migrations by recording the total number of burrowing owls and the

number of marked owls seen each month throughout the year (Figure 2.3). Our sites had

3 to 7 times as many burrowing owls during the summer breeding period (between March

and September) as they did during the winter (October through February).

To determine whether burrowing owls were resident or migrant, we recorded the

number of birds marked in one season and re-sighted in another. Owls were designated

as known residents if they were observed in ≥3 consecutive seasons. There were more

(χ2 = 10.20; 1 d.f.; P = 0.0014) known resident winter-marked owls (44.4 %; 4 of 9) than

summer-marked (3.7%; 4 of 108) owls (Table 2.2). Some additional owls may have been

resident, including summer-marked owls that were observed the summer following the

summer in which they were marked (9.3%; 10 of 108). These owls may have over-

wintered in the region undetected at sites that we did not survey, or they may have

migrated south and returned to the same sites to breed the following summer.

Additionally, 2.6% of our marked owls (3 of 117) were seen in only 2 consecutive

seasons (1 seen winter and the following summer; and, 2 seen summer and the following

winter). We therefore determined that most burrowing owls in this area were summer

migrants, with only a small proportion (6.8%-18.0%; or 8-21 of 117 total marked owls)

likely resident (remaining over-winter between consecutive breeding seasons) in this

population. Furthermore, in over 406 days of searching our 6 intensive sites and 43 days

of searching adjacent sites within 8 km of the intensive sites, no marked owl was ever

observed at any site other than the one at which it was captured.

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Nesting

We identified 98 nesting pairs on our 6 sites during 2003 (n = 57) and 2004(n =

41). Number of nesting pairs/ha and productivity (maximum number of chicks seen per

breeding pair) did not differ (Wilcoxon matched pairs T > 4; P > 0.173) between years for

sites. Furthermore, the number of burrowing owl pairs/ha did not differ between years

among sites (χ2 = 5.691; 5 d.f.; P = 0.3374) and owl productivity did not differ between

years among sites (χ2 = 0.9523; 5 d.f.; P = 0.9663). Therefore, we pooled years for

analyses of nesting pairs and productivity. There were 1.02 ± 0.40 (mean + SE) nesting

pairs/ha on our sites. Productivity averaged 2.80 ±0.13 (mean + SE) chicks per pair

(Table 2.3). Mean distance between burrows of nesting pairs was 66.33 m ± 4.22. The

earliest date we recorded chicks seen was May 19, with the last observed emergence of

new chicks recorded on June 25.

The number of burrowing owl pairs (Figure 2.4) was positively correlated (r2 =

0.5498, P = 0.0060) to prairie dog colony size (n=12). In 2004 we also had counts of the

number of holes on each prairie dog town. The number of burrowing owl pairs was

positively correlated (r2 = 0.7327, P = 0.0296) to the number of prairie dog holes on our 6

sites in 2004 (Figure 2.5).

For our 6 intensive sites the number of prairie dog holes increased with colony

size (r2 = 0.7006, 4 d.f., P = 0.0377). However, number of burrowing owl pairs was not

related to either the density of prairie dogs (estimated prairie dogs/ha) (r2 < 0.3, P > 0.1)

or the index of vacant holes (holes/estimated prairie dogs) (r2 < 0.3, P > 0.1) for our 6

intensively monitored sites.

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We had measures of pairs of burrowing owls, owl productivity, and indices of

relative food abundance (distance to playas containing water and relative abundance of

small mammals) on all sites in both 2003 and 2004 (n=12 sites). However, our measures

of relative food abundance did not show significant relationships to burrowing owl pairs

or productivity (r2 < 0.1, P > 0.1). Measures of visual obstruction and vegetative

composition were not correlated to burrowing owl numbers or productivity (r2 < 0.4. P >

0.1) (Appendix B).

We plotted burrowing owl nest locations for 2003 and 2004 and prairie dog holes

for 2004 using ArcView GIS (Appendix C). We created 50-m buffers from prairie dog

colony centers and counted the number of owl nesting burrows per unit area. Given the

size of prairie dog colonies on our sites, all holes were within 3 of these 50-m buffers

from the colony center. There were more nesting burrows in zones farther from the

colony center (Table 2.5) but since buffers farther from the center also incorporated much

more area, the number of nesting burrows was not greater than expected if owls nested at

equal densities in each zone the from the center to the outer edges of prairie dog colonies

(χ2 = 2.401, 2 d.f., P = 0.3009). Average distance to the colony edge for burrowing owl

burrows (45 ± 3.8 Meters) was less than the average distance to the colony center (142 ±

6.9 meters, T = -12, 192 d.f., P < .001). To see whether burrowing owls were nesting in

specific orientations on the prairie dog colonies, we divided prairie dog colonies into 4

quadrants (based on cardinal directions) and compared aspects used for nesting burrows.

There was no difference in the number of nesting burrows (χ2 = 1.69, 3 d.f., P = 0.6483)

or nesting burrows per unit area (χ2 = 2.45, 3 d.f., P = 0.4850) by aspect.

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Burrowing owls did not use more or less dense areas of holes within the prairie

dog colonies. There was no difference (P > 0.10) between distances from burrowing owl

nests and total hole distances, or between the 5 closest holes to burrowing nests and the 5

closest to randomly selected holes.

Discussion

We found noose carpets and Bal-Chatri traps to be most successful for capturing

adult burrowing owls during the nesting season. Bal-Chatri traps with a live mouse were

often required to capture the male during the nest-provisioning period. Mealey (1977)

and Milsap and Bear (1997) also found noose carpets to be successful in Florida. During

the winter, walk-in or 1-way cage door traps placed on burrows after owls were observed

entering were almost the only methods that were successful on our sites. Both wintering

and breeding owls seemed to prefer flight to the shelter of burrows, making it difficult to

use walk-in traps. Clayton and Schmutz (1999) saw a similar pattern with owls in their

study in Alberta. We did capture 3 adult burrowing owls with bow-nets during winter by

placing the bow-net at a frequented burrow, then baiting it with a white mouse.

Most owls on our sites were summer migrants. Only 6.8%-18.0% of the owls we

marked were observed over-wintering or breeding on our sites in a second season. This

is much lower than reported returns of in Florida (68%; Millsap and Bear 1997) or in

California (20-25%; Coulombe 1971). A higher proportion of wintering owls than

summering owls were re-sighted again in another season in our study. Our returns are

similar, although somewhat higher, than those previously reported for other studies in the

15

southern Great Plains. Butts (1976) reported less than 1% of the summer owl population

present in late July, returned to his Oklahoma Panhandle sites to breed in the following

year, whereas in Dallam County, Texas, 2.7% of the owl population from late July of the

previous year returned. However, all banded owls known to have over-wintered at his

sites remained to breed that following breeding season. Our higher numbers may reflect

a change since 1970’s with fewer owls using the northern parts of their continental range

(Clayton and Schmutz 1999) and more remaining or breeding in Texas.

To date we have had only 2 band recoveries from the 153 owls we banded. One

was killed by a car adjacent to the Lubbock site it was trapped at during the same season,

and the other was recovered in Apatzingan, Michoacán, México, in January of 2004, 7

months after it was banded in Lubbock County during June of 2003. This band return is

similar to Butts (1976) who reported one banded female from the breeding season in the

Oklahoma Panhandle, which was shot 17 months later during early winter in Zpaotlanejo,

Jalisco, México. Another similar record is from an owl captured and banded in this

region by Ross and Smith (1970) that was recorded in March of 1968 and 1969, captured

in Swisher County and recaptured the following year at El Paso, Texas.

We observed 2.80 ± 0.13 (mean + SE) chicks per pair, which is comparable to

reports from California (Thomsen 1971), Florida (Mealey 1997, Millsap and Bear 2000),

Montana (Restani et al. 2001), and New Mexico (Arrowood et al. 2001). However,

productivity on our sites was less than that reported in central Argentina (Bellocq 1997),

Saskatchewan (Haug and Oliphant 1990, James et al. 1997, Wellicome 1997), and North

Dakota (Konrad and Gilmer 1984).

16

Distances between burrows may be representative of burrowing owl density or

territoriality. We compared mean distance between burrows at our sites to distances we

computed from data presented in Desmond et al. (1995). We used Desmond’s colonies

that were under 20 ha (comparable to ours), which averaged 68.23 m (Desmond et al.

1995). Other studies have reported much larger distances between burrows, particularly

for burrowing owls nesting in abandoned badger burrows (Green and Anthony 1989,

Haug and Oliphant 1990), squirrel burrows (Martin 1973) and those that dig their own

burrows in Florida (Millsap and Bear 2000).

Vegetative differences over all sites and years were not related to either

burrowing owl nests or productivity. Others have found burrowing owl nesting was

related to vegetative cover with owls selecting sites with lower visual obstruction

(Schmutz 1997, Trulio 1997, Clayton and Schmutz 1999). All 6 of our study sites were

located on prairie dog colonies, mostly on grazed shortgrass prairie or neglected sites in

an agricultural-suburban interface where there was minimal visual obstruction (2.7 ± 0.16

cm).

There is disagreement in the literature on whether burrowing owl numbers are

related to prairie dog colony size. Orth and Kennedy (2001) in Colorado and Restani et

al. (2001) in Montana found no relation between colony size and number of burrowing

owls whereas Desmond and Savage (1996) found a positive correlation between colony

size and number of burrowing owls in Nebraska. We found a positive relation between

prairie dog colony size and number of burrowing owl pairs. However, we believe this is

due more to the increased number of holes, hence, nesting opportunities than prairie dog

17

colony size alone. It appears that the expectation of more burrowing owls is more

strongly related to the number of holes than the colony size. Although we do not know

how many holes were actually vacant, it did not appear that the number of “vacant” holes

in prairie dog colonies limited burrowing owls, as there were more holes with little or no

evidence of prairie dog activity than pairs of owls.

We did not detect specific spatial patterns of burrowing owl nesting in prairie dog

colonies. Desmond et al. (1995) assumed that burrowing owls in small (<35 ha) colonies

(such as ours) could not demonstrate spatial patterns due to size limitations, and that in

larger colonies they distributed a more clumped pattern. We suspect that use may be

based mostly on availability of vacant burrows; however, Powell et al. (1994) point out

that numbers of holes may not be directly related to number of prairie dogs or occupancy.

Our measure of vacancy was an indirect estimate with no spatial information. Vacant

burrows may be spatially clumped or widely scattered depending upon historical changes

in prairie dog occupancy within the colony. Established prairie dog colonies show

patterns of expansion, with older portions of the colony becoming less used or vacant

(Whicker and Detling 1988). This may result in clumped areas of vacant prairie dog

holes for burrowing owls. However, extrinsic disturbances (e.g., prairie dog control or

plague) may result in different patterns of hole availability for burrowing owls. Sidle et

al. (2001) found that burrowing owls appear to prefer prairie dog colonies in the Great

Plains National Grasslands that are active compared to those that are inactive; they cited

lack of burrow maintenance by prairie dogs and possible increases in predation as

potential reasons. With other prey (prairie dogs) absent, predators may focus more on

18

burrowing owls. We found burrowing owl numbers particularly high on the 12-36 site

even following prairie dog control with Phostoxin. However, treatments were conducted

during winter and this site was always rapidly recolonized by prairie dogs from nearby

untreated areas. So holes were seldom closed for very long.

Management Implications

Trapping of breeding burrowing owls appears to be more effective when nestlings

first emerge. Future breeding captures should be attempted immediately following

emergence of chicks using noose carpets and Bal-chatri traps when necessary. Winter

trapping should concentrate on walk-in traps and baited bow-nets.

More research is needed on burrowing owl ecology in our area. To better assess

potential burrowing owl food sources, we need data on where burrowing owls are

foraging and what prey items they are using in this area. Radio telemetry studies may

provide some of these answers in the near future, allowing for better sampling of

potential burrowing owl habitat use and prey base. Better estimates of burrowing owl

residency and timing of migration are needed with a more focused approach on one area

of the Panhandle where a more thorough sample of the population can be monitored.

Future band returns may lead to additional data on migration and fidelity of local

breeding populations of burrowing owls, as well as dispersal of chicks.

Prairie dogs are clearly important to burrowing owls in our area; however, the

characteristics that make one prairie dog colony more suitable than the next are largely

unknown. It does seem that the lack of visual obstruction provided by prairie dogs and

19

the large number of potentially vacant burrows are key elements in making good

burrowing owl habitat. Treatment of prairie dogs may initially reduce hole occupancy by

prairie dogs, leaving more available burrows for owls, although the quality of available

burrows may be lacking as well as the supply of future burrowing owl nest sites.

Additionally, the lack of prairie dogs in a colony can lead to an increase in visual

obstruction and potential loss of valuable nesting habitat.

20

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24

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26

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27

Table 2.1. Six intensively monitored sites from Lubbock and Carson Counties, Texas, and data known prior to the start of the 2003-2004 field seasons.

Study Site County Historic Surrounding Area (ha) Owls

Treatment1 Land Use (2002) 2

School Lubbock None Urban 12.78 18

X-Fab Lubbock None/PT3 Industrial/Urban 37.15 14

L 103 Lubbock None Urban/fallow 14.37 27

12-36 Carson PT Industrial 11.61 15

Zone 4 Carson PT Agriculture 5.20 2

Pantex Lake Carson None Agriculture 22.63 10

1 PT denotes known (2000-2004) prairie dog control efforts using Phostoxin. 2 Numbers of burrowing owls counted during prairie dog surveys in 2002 (Pruett 2004). 3 Phostoxin treatments applied during winter 2004.

28

Table 2.2. Summary of burrowing owl captures and re-sightings by season for burrowing owls captured at 6 study sites in Lubbock and Carson Counties, Texas, between January 2003 and May 2005, including 3 additional winter owls captured on adjacent Carson County sites in February 2004.

Number Number Number Number Number Number Number

of owls color never seen season seen in ≥ 1 same season known

Season banded banded seen again banded1 other season next year2 resident3

Winter 16 9 3 4 1 0 4

Summer 123 108 51 57 2 10 4

29

1 Burrowing owls seen in season they were banded (includes late migrating owls that were no longer observed within 2 weeks of the end of the season of capture). 2 Burrowing owls seen, in this case, the summer after the summer that they were banded. These birds may have remained in the area but wintered at sites where we did not observe them. 3 Burrowing owls seen in ≥ 3 consecutive seasons.

Table 2.3. Burrowing owl nesting data for the 6 intensively monitored sites in Lubbock and Carson Counties, Texas, for 2003 and 2004. Site Year No. Pairs No. chicks/pair1 Area (ha) Spacing2

L103 2003 13 3.3 11.71 49.03 ± 7.86

School 2003 8 2.0 7.55 55.91 ± 21.75

X-Fab 2003 13 2.5 14.48 67.22 ± 12.94

12-36 2003 9 3.4 11.86 62.80 ± 16.06

Pantex Lake 2003 11 2.9 7.50 64.75 ± 10.67

Zone 4 2003 3 3.7 1.57 71.85 ± 7.96

L103 2004 8 2.5 11.71 81.62 ± 21.01

School 2004 6 3.0 7.55 91.56 ± 26.43

X-Fab 2004 5 3.0 11.12 77.78 ± 25.32

12-36 2004 13 3.2 11.86 59.85 ± 8.28

Pantex Lake 2004 5 1.8 7.50 85.00 ± 3.03

Zone 4 2004 4 1.5 3.08 44.59 ± 7.38

1 Mean maximum number of chicks seen above ground for successful nesting burrowing owl pairs. 2 Mean and standard error for distances between burrowing owl nesting burrows in meters.

30

Table 2.4. Number of prairie dog holes marked in 2004 and estimated number of prairie dogs for 6 intensively monitored sites in Lubbock and Carson Counties, Texas.

Colony Area (ha) Prairie Dogs1 Holes Density2 Vacancy3

L103 11.71 80 938 80.10 11.73

School 7.55 142 595 78.77 4.19

X-Fab 11.12 22 649 58.36 29.50

12-36 11.86 84 1179 99.39 14.04

Pantex Lake 7.50 145 810 107.93 5.59

Zone 4 3.08 28 266 86.44 9.50

1 Number of prairie dogs estimated using model based on 3 independent surveys (Pruett 2004). 2 Number of prairie dog holes per hectare. 3 Estimate of vacant burrows based on number of prairie dog holes per prairie dog.

31

Table 2.5. Number of burrowing owl pairs and area per 50-meter buffer on 6 intensively monitored sites in Lubbock and Carson Counties, Texas, in 2003 and 2004.

Buffer zone 1 Buffer zone 2 Buffer zone 3

No. Area No. Area No. Area

Colony Year Pairs (ha) Pairs (ha) Pairs (ha)

L103 2003 1 0.17 6 4.01 2 7.53

School 2003 0 0.21 1 2.20 4 6.89

X-Fab 2003 2 2.75 5 4.84 6 6.89

12-36 2003 0 1.45 4 3.99 4 6.43

Pantex Lake 2003 0 0.13 2 2.11 7 3.08

Zone 41 2003 3 3.08

L103 2004 0 0.17 2 4.01 6 7.53

School 2004 0 0.21 1 2.20 5 6.89

X-Fab 2004 0 2.75 4 4.84 1 6.89

12-36 2004 4 1.45 4 3.99 6 6.43

Pantex Lake 2004 0 0.13 2 2.11 4 3.08

Zone 41 2004 6 3.08

1Colony not wide enough for buffers.

32

LIST OF FIGURES

2.1 The maximum number of burrowing owls seen on prairie dog colonies correlated to prairie dog colony size for a 12 county area searched for a prairie dog colony study in the Texas Panhandle……………………………….. 34 2.2 The number of burrowing owls caught by trap type and season across all sites in Lubbock and Carson Counties, Texas in 2003 and 2004……………. 35 2.3 Number of burrowing owls seen in 2003 and 2004, with and without bands for the 6 study sites in Lubbock and Carson Counties, Texas…………… 36 2.4 The number of burrowing owl pairs recorded in relation to prairie dog colony area in hectares for the 6 study sites in Lubbock and Carson Counties, Texas for 2003 and 2004……………………………………………... 37 2.5 The number of burrowing owl pairs recorded in relation to the number of prairie dog holes marked in 2004 for the 6 study sites in Lubbock and Carson Counties, Texas…………………..………………………………… 38

33

Figure 2.1

0 20 40 60 80 100 120 140 160 180 200 220 240 260 280

Colony Area (ha)

0

5

10

15

20

25

30

35

40

45

50

Max

Adu

lt B

UO

W

r2 = 0.0182 P = 0.0107

34

Figure 2.2

0

10

20

30

40

50

60

70

80

Bal-Chatri

Hand Walk-in NooseCarpet

Bow-net

No.

of b

urro

w o

wls

SummerWinter

35

Figure 2.3

0

20

40

60

80

100

120

June

July

Augus

tSep

tembe

r

Octobe

rNov

embe

rDec

embe

r

Janu

ary

Februa

ry

March

April

May

No.

of B

UO

W's

.

Banded 03Total 03Banded 04Total 04

1

2

36

1 We trapped and banded burrowing owls in this summer period (n = 63 in 2003; n = 32 in 2004) and these data include marks from the same season. 2 Adequate data was not collected for burrowing owls in August of 2003 or 2004; however, in 2004 5 banded and 13 total owls were observed on intensively monitored sites in Lubbock.

Figure 2.4

0 2 4 6 8 10 12 14 16

Area (ha)

2

4

6

8

10

12

14B

UO

W P

airs

r2 = 0.5498 = 0.0060 P

37

Figure 2.5

200 400 600 800 1000 1200 1400

Prairie dog holes

2

4

6

8

10

12

14BU

OW

Pai

rs

r2 = 0.7327 P = 0.0296

38

APPENDIX A

BURROWING OWL TRAPPING DATA

Table A.1. Burrowing owl trapping data for all burrowing owls captured in 2003 and 2004, including 13 adults and 1 juvenile captured for a concurrent project.

USFWS Date Code1 Age Sex Colony Weight Tarsus Tarsus Wing

(g) width depth2 Chord3

170538704 1/29/3 A X-FAB 172 3.3 4.5 168

80400627 2/7/3 A SCHOOL 190 3.6 4.8 177 39

80400628 2/11/3 A SCHOOL 172 3.4 4.7 164

80400629 2/12/3 A SCHOOL 176 3.5 4.8

80400630 2/16/3 A SCHOOL 162 3.2 5.0 166

80400630 4/30/4 79/H A M SCHOOL 141 3.2 4.9 169

80400631 2/22/3 A SCHOOL 163 3.6 4.9 172

80400632 2/22/3 A SCHOOL 180 3.9 4.7 172

80400633 2/23/3 A X-FAB 165 3.7 4.8 163

Table A.1. Continued.

USFWS Date Code1 Age Sex Colony Weight TW TL WC

80400634 2/25/3 A X-FAB 155 3.4 4.7 174

80400634 6/5/3 16/H A M X-FAB 149 3.4 4.8 175

80400635 5/28/3 00/H A M L-103 143 3.6 4.9 186

80400636 5/29/3 01/H A L-103 152 3.4 5.1 174

80400637 5/29/3 02/H A F L-103 154 3.3 5.3 172

80400638 5/29/3 J L-103 88 4.0 4.4 40

80400639 5/29/3 J L-103 84 3.8 4.6

80400640 5/31/3 03/H A F L-103 143 3.6 4.7 176

80400641 5/31/3 04/H A M L-103 3.5 4.9

80400642 6/1/3 05/H A F L-103 142 3.5 4.5 166

80400643 6/1/3 06/H F F L-103 137 3.4 5.0 173

80400644 6/2/3 07/H A M L-103 134 3.3 4.5 171

80400645 6/2/3 08/H A F L-103 149 3.1 4.5 173



80400646 6/3/3 09/H A F L-103 136 3.7 4.8

80400647 6/4/3 10/H A F X-FAB 140 3.2 4.6 160

80400648 6/5/3 11/H A F X-FAB 147 3.4 4.6 183

80400649 6/5/3 12/H A F X-FAB 172 3.4 5.0

80400650 6/5/3 13/H A F X-FAB 3.0 4.9

80400651 6/5/3 14/H A M X-FAB 147 3.6 5.1 184 41

80400652 6/5/3 15/H A M X-FAB 146 3.7 4.9 173

80400653 6/6/3 17/H A M SCHOOL 150 3.3 4.8 173

80400654 6/6/3 J SCHOOL 122 3.8 4.5

80400655 6/6/3 18/H A F SCHOOL 143 3.4 4.8 172

80400656 6/9/3 19/H A F L-103 129 3.4 4.3 172

80400657 6/9/3 20/H A M L-103 145 3.5 4.5 186

80400658 6/9/3 21/H A F L-103 145 3.1 4.2 172



80400659 6/9/3 22/H A M L-103 143 3.5 5.1 175

80400660 6/11/3 23/H A M ZONE 4 156 3.6 4.6 176

80400661 6/11/3 24/H A F ZONE 4 146 3.4 4.7 162

80400662 6/11/3 25/H A F ZONE 4 125 3.2 4.5 162

80400663 6/12/3 26/H A F 12-36 149 3.4 4.7 173

80400664 6/12/3 27/H A M 12-36 142 3.2 4.3 173 42

80400665 6/12/3 28/H A F 12-36 146 3.3 5.0 169

80400666 6/12/3 29/H A F 12-36 165 3.3 4.9 184

80400667 6/12/3 30/H A F 12-36 145 3.3 5.3 172

80400668 6/12/3 31/H A F 12-36 135 3.2 4.3 172

80400669 6/12/3 32/H A M 12-36 150 3.6 4.6 178

80400670 6/12/3 33/H A F 12-36 155 3.8 4.7

80400671 6/12/3 34/H A M 12-36 155 3.6 5.0 164



80400672 6/13/3 35/H A F PLAKE1 140 3.4 4.7 173

80400673 6/13/3 36/H A F PLAKE 154 3.5 4.8 177

80400674 6/13/3 37/H A F PLAKE 163 3.2 4.6 168

80400675 6/13/3 38/H A F PLAKE 137 3.3 4.7 185

80400676 6/15/3 39/H A M X-FAB 145 3.5 5.0 171

80400677 6/15/3 40/H A M X-FAB 145 3.4 4.9 180 43

80400678 6/15/3 41/H A F X-FAB 141 3.9 5.2 175

80400679 6/15/3 42/H A F X-FAB 123 3.2 4.8 168

80400680 6/16/3 43/H A L-103 151 3.2 5.0 177

80400681 6/18/3 44/H A F X-FAB 137 3.2 4.8 168

80400682 6/18/3 45/H A F X-FAB 179 3.4 4.9 174

80400683 6/18/3 46/H A M X-FAB 141 3.6 5.0 173

80400684 6/18/3 47/H A M X-FAB 135 3.4 4.9 163



80400685 6/9/3 48/H A F L-103 155 3.2 5.1 176

80400686 6/23/3 49/H A M ZONE 4 150 3.5 4.7 165

80400687 6/23/3 50/H A F ZONE 4 152 3.2 4.9 177

80400688 6/24/3 51/H A F 12-36 144 3.4 4.7 160

80400689 6/25/3 52/H A F PLAKE 155 3.2 5.2

80400690 6/25/3 53/H A F PLAKE 151 3.3 4.6 172 44

80400691 6/25/3 54/H A F PLAKE 137 3.3 4.5 162

80400692 6/25/3 55/H A F PLAKE 148 3.6 5.2 179

80400693 6/25/3 56/H A F PLAKE 145 3.7 4.9 177

80400694 6/25/3 57/H A PLAKE 149 3.5 5.1 182

80400695 6/25/3 58/H A PLAKE 150 3.7 4.4 166

80400696 6/25/3 59/H A F PLAKE 146 3.3 4.6 168

80400697 6/25/3 60/H A F PLAKE 152 3.6 4.4 177



80400698 6/25/3 61/H A F PLAKE 141 3.3 5.3 169

80400699 6/26/3 62/H A ZONE 4 144 3.3 5.0 167

80400700 6/26/3 63/H A M 1236 180 3.6 4.9

84473501 6/11/3 J ZONE 4 49 3.9 4.2

84473502 6/18/3 J X-FAB 142 3.3 4.5 142

84473503 6/26/3 J ZONE 4 100 3.9 5.7 45

84473504 6/26/3 64/H A F PLAKE 135 3.2 4.8 162

84473505 6/28/3 J X-FAB 160 3.7 4.7

84473506 6/28/3 65/H A M X-FAB 143 3.6 5.0 172

84473507 6/30/3 66/H A F SCHOOL 151 3.4 5.2

84473508 6/30/3 67/H A SCHOOL 167 3.4 3.9 179

84473509 7/2/6 68/H A F SCHOOL 170 3.4 5.3 166

84473510 7/7/3 69/H A F 12-36 135 3.4 4.5 169



84473511 7/7/3 70/H A M 12-36 144 3.6 4.9 171

84473512 7/7/3 71/H A M 12-36 149 3.6 4.8 171

84473513 1/31/4 72/H A X-FAB 150 3.2 5.0 169

84473514 1/31/4 73/H A X-FAB 123 3.0 4.6 165

84473515 2/7/4 74/H A ZONE 82 157 3.4 4.8 168

84473516 2/11/4 75/H A PANTEX 160 3.5 4.9 179 46

84473517 2/11/4 76/H A PLAKE 187 3.7 5.0

84473518 2/17/4 77/H A SCHOOL 163 4.7 3.6 178

84473519 5/18/4 80/H A M L-103 141 3.4 4.8 173

84473521 6/4/4 81/H A F ZONE 4 132 3.3 4.4 174

84473522 6/5/4 82/H A F X-FAB 136 4.1 5.0 172

84473523 6/5/4 83/H A F SCHOOL 125 3.3 4.2 171

84473524 6/5/4 84/H A F L-103



84473525 6/5/4 85/H A F L-103 140 3.3 4.8 177

84473526 6/5/4 86/H A F L-103 152 3.5 5.7 176

84473527 6/8/4 87/H A M L-953 149 3.4 5.3 174

84473528 6/8/4 88/H A F L-95 192 3.3 4.9 178

84473529 6/8/4 89/H A M L-95 136 3.6 4.5 171

84473530 6/8/4 90/H A M L-95 152 3.5 4.6 175 47

84473531 6/8/4 91/H A M L-95 148 3.6 4.7 168

84473532 6/9/4 92/H A F ZONE 8 180 3.8 4.7

84473533 6/9/4 93/H A M ZONE 8 166 3.4 4.8 183

84473534 6/9/4 94/H A M ZONE 8 156 3.2 4.6 172

84473535 6/9/4 95/H A M ZONE 8 156 3.9 4.9

84473536 6/9/4 96/H A F ZONE 8 153 3.2 4.7

84473537 6/10/4 97/H A M ZONE 4 157 3.7 5.1



84473538 6/10/4 98/H A M ZONE 8 130 3.2 4.8 167

84473539 6/12/4 99/H A M L-103 137 3.4 5.0 173

84473540 6/12/4 00/K A M SCHOOL 142 3.3 4.9 176

84473541 6/15/4 01/K A M ZONE 8 137 3.7 4.8 162

84473542 6/15/4 02/K A F ZONE 8 142 3.2 4.4 164

84473543 6/15/4 J ZONE 8 104 3.5 4.1 48

84473544 6/17/4 03/K A F PLAKE 152 3.2 172

84473545 6/17/4 J PLAKE 113

84473546 6/17/4 04/K A M PLAKE 162 3.7 5.5 178

84473547 6/17/4 J PLAKE 84 3.8 4.9

84473548 6/17/4 05/K A M PLAKE 143 3.6 4.8 178

84473549 6/18/4 06/K A F ZONE 4 144 3.2 5.1 176

84473550 6/18/4 07/K A F 12-36 135 3.4 4.4 170



84473551 6/18/4 J 12-36 166 3.4 4.6 158

84473552 6/18/4 08/K A M 12-36 134 3.3 4.8 172

84473553 6/18/4 09/K A F 12-36 156 3.4 4.6 173

84473554 6/20/4 10/K A F SCHOOL 122 3.1 4.2 172

84473555 6/20/4 11/K A M SCHOOL 155 3.2 4.4 176

84473556 6/20/4 12/K A F SCHOOL 149 3.3 4.6 176 49

84473557 6/20/4 13/K A F SCHOOL 135 3.3 5.0 173

84473558 6/22/4 14/K A F ZONE 4 119 2.9 4.0 160

84473559 6/23/4 15/K A M 12-36 150 3.3 4.9 178

84473560 6/23/4 16/K A F 12-36 138 3.1 5.1 174

84473561 6/23/4 J 12-36 143 3.6 5.0

84473562 6/23/4 17/K A M 12-36 130 3.2 4.6

84473563 6/24/4 18/K A M PLAKE 149 3.2 4.7



84473564 6/23/4 J 12-36 139 3.8 4.8

84473565 6/24/4 19/K A F PLAKE 149 3.6 4.6 177

84473566 6/24/4 20/K A F PLAKE 140 3.2 4.7

84473567 6/27/4 21/K A M L-103 138 3.3 5.4 170

84473568 6/28/4 22/K A F SCHOOL 144 3.4 4.6 166

84473569 6/28/4 24/K A F X-FAB 149 3.4 5.1 149 50

84473570 6/28/4 23/K A M X-FAB 138 3.1 4.8 171

84473571 6/28/4 J X-FAB 3.4 4.2

84473572 6/30/4 25/K A F 12-36 155 3.7 5.3

84473573 7/2/4 26/K A M PLAKE 148 3.8 4.9

84473574 7/1/4 J ZONE 4

84473575 7/2/4 27/K A F PLAKE 131 3.7 4.8 165

84473576 7/6/4 28/K A M L-103 137 3.4 4.9 172



84473577 7/10/4 J ZONE 4 145 3.9 5.9

84473578 7/17/4 29/K A M 12-36 141 3.4 4.7 176

1 Pantex Lake 2 Additional Pantex site for winter trapping, later used for concurrent study.

ed for concurrent study. 3 Additional Lubbock site us

51

APPENDIX B

VEGETATION TRANSECT DATA

Table B.1. RAW data from (n=2) transects per site. Percent cover of vegetative parameters measured on prairie dog colonies occupied by burrowing owls for intensively measured study sites in Lubbock and Carson Counties, Texas during July and August of 2003 and 2004. Site Year % grass % forbs % bare % litter % other Visual No. Burrowing Owl

Obstruction Pairs Productivity

L103 2003 26.16 16.20 8.48 49.16 0.00 1.3 13 3.3

0.00 51.44 14.28 34.28 0.00 1.0 52

School 2003 26.72 6.44 37.08 29.76 0.00 1.2 8 2.0

18.00 22.24 25.20 34.56 0.00 1.2

X-Fab 2003 0.00 19.04 8.92 72.04 0.00 1.2 13 2.5

0.00 12.56 29.64 57.80 0.00 1.0

12-36 2003 19.28 14.08 9.60 57.04 0.00 1.0 9 3.4

65.48 1.28 0.84 32.40 0.00 1.3

Table B.1. Continued.

Site Year % grass % forbs % bare % litter % other Visual No. Burrowing Owl


Pantex Lake 2003 22.44 10.12 13.36 54.08 0.00 1.0 11 2.9

47.44 7.28 1.60 43.68 0.00 1.0

Zone 4 2003 71.56 0.32 11.92 16.20 0.00 1.7 3 3.6

L103 2004 13.04 23.24 9.64 54.08 0.00 1.5 13 3.3

0.00 23.88 24.60 51.52 0.00 1.2 53

School 2004 4.04 14.12 67.28 14.56 0.00 1.0 6 3.0

16.32 25.72 23.56 34.40 0.00 1.3

X-Fab 2004 0.00 26.72 8.04 65.24 0.00 1.3 5 3.0

0.04 32.44 7.92 59.60 0.00 1.7

12-36 2004 35.12 17.20 12.76 34.56 0.36 1.3 13 3.2

34.72 13.28 3.44 48.56 0.00 2.2

Table B.1. Continued.

Site Year % grass % forbs % bare % litter % other Visual No. Burrowing Owl


Pantex Lake 2004 8.68 21.76 8.28 61.28 0.00 1.7 5 1.8

62.68 10.16 0.96 26.00 0.20 1.2

Zone 4 2004 78.36 6.20 3.04 12.40 0.00 1.4 4 1.5

54

APPENDIX C

COLONY MAPS

55

Map C.1. 12-36 map

56

Map C.2. L103 map.

57

Map C.3. Pantex Lake map.

58

Map C.4. School map.

59

Map C.5. X-Fab map.

60

Map C.6. Zone 4 map.

61

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