Nest Success and Reproductive Ecology of the
Texas Botteri’s Sparrow (Peucaea botterii texana) in
Exotic and Native Grasses
Katherine S. Miller, Erin M. McCarthy, Marc C. Woodin, and Kim Withers
Southeastern Naturalist, Volume 12, Issue 2 (2013): 387–398
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2013 SOUTHEASTERN NATURALIST 12(2):387–398
Nest Success and Reproductive Ecology of the
Texas Botteri’s Sparrow (Peucaea botterii texana) in
Exotic and Native Grasses
Katherine S. Miller1,*, Erin M. McCarthy1, Marc C. Woodin2, and Kim Withers3
Abstract - Very little information is available for Peucaea botterii texana (Texas Botteri’s
Sparrow) and nothing is known about its nesting ecology, in part due to its cryptic
behavior and nesting strategies. Our goal was to examine the nesting ecology of Texas
Botteri’s Sparrows and compare reproductive success between exotic and native grasslands.
We searched for and monitored nests in 2004 and 2005 on the King Ranch in
southern Texas. We found no relationship in reproductive effort, nest characteristics, and
plant species richness around the nest between grassland types. Vegetation surrounding
Texas Botteri’s Sparrow nests was significantly taller and denser in native grasslands than
in exotic grasslands. Further research on nesting ecology for the Texas Botteri’s Sparrow
is necessary to determine its habitat needs and its role as an indicator of grassland quality.
Many North American grassland bird species are declining at faster rates than
any other bird group, mostly due to habitat loss from fragmentation, deterioration
from human urbanization, and agricultural conversion (Vickery and Herkert
2001, Winter and Faaborg 1999). Fragmentation can increase predation, the primary
cause of nest failure for most ground-nesting passerines (Dion et al. 2000,
Herkert et al. 2003, Jones 2003). Fragmentation can also lower reproductive success,
the number of fertile offspring per mated pair.
Exotic invasive species are another problem; monocultures of exotic grasses
often have few native grass and forb species, which may reduce the abundance
and diversity of insects, seeds, and cover (Bock et al. 1986, Flanders et al. 2006).
Battin (2004) and Jones (2003) addressed ecological traps, where animals may
prefer a low-quality habitat to a habitat of higher quality. Certain studies (Jones
2003, Lloyd and Martin 2005) have found grassland birds nesting in exotic
grasses as often as in native grasses, which are usually assumed to be the higherquality
habitat. Nearly half of the federally threatened and endangered species,
including grasses, are at risk due to competition and predation from non-indigenous
species (Wilcove et al. 1998).
Although grassland bird reproductive success may be linked to population
declines, this can be hard to determine because nests can be difficult to locate
and monitor (Davis 2003). Nests of Peucaea botterii Sclater (Botteri’s Sparrow),
a ground-nesting, tall-grass specialist (Webb and Bock 1996), are notoriously
1Department of Physical and Life Sciences, Texas A&M University-Corpus Christi,
Corpus Christi, TX 78412. 2Tejas EcoServices, Inc., Corpus Christi, TX 78412. 3Center
for Coastal Studies, Texas A&M University-Corpus Christi, Corpus Christi, TX 78412.
*Corresponding author - Katherine.Miller@students.tamuk.edu.
388 Southeastern Naturalist Vol. 12, No. 2
difficult to find. Texas Parks and Wildlife Department lists P. b. texana (Texas
Botteri’s Sparrow) as threatened (www.tpwd.state.tx.us), due to its restricted
breeding range and its characterization as an indicator of an open, grassy, ungrazed
environment (Marshall and Clapp 1985). The Texas Botteri’s Sparrow
breeds in a coastal strip along the Gulf of Mexico, from the Rio Grande north to
Copano Bay in San Patricio County (about 180 km), and south to Tampico, Veracruz,
Mexico (about 400 km) (Marshall and Clapp 1985, Swanson 1985, Webb
and Bock 1996).
While a number of studies have focused on P. b. arizonae (Arizona Botteri’s
Sparrow; Bock and Bock 1978, Jones and Bock 2001, Kirkpatrick et al. 2002,
Maurer et al. 1989), very little research has focused on the nesting habits of
Texas Botteri’s Sparrows. In a study conducted at Laguna Atascosa National
Wildlife Refuge in extreme southern Texas, Marshall and Clapp (1985) primarily
focused on singing males and breeding territories, and conducted density
surveys. Although observations of its habitat (Harper 1930) and relationship
to other species in the Aimophila (now Peucaea) genus (Wolf 1977) have been
made previously, this is the first research to focus on the nesting ecology of the
Texas Botteri’s Sparrow.
With so little data available, our goal was to collect basic information on the
nesting ecology of the Botteri’s Sparrow in southern Texas. Our objectives were
to examine overall reproductive effort of Texas Botteri’s Sparrows, as measured
by clutch size and nesting success, and to examine effects of nest placement by
comparing reproductive effort, nest characteristics, and nest site microhabitat for
nests in exotic and native grasses.
Breeding habitat of Texas Botteri’s Sparrows is characterized by three ecological
regions (Texas Parks and Wildlife Department 1995). Prairies and marshes of
the lower Gulf Coast are dominated by Spartina spartinae (Trin.) Merr. ex A.S.
Hitchc. (Gulf Cordgrass) and Borrichia frutescens (L.) DC. (Sea Oxeye Daisy).
Coastal sand plains are characterized by Schizachyrium scoparium L. (Little
Bluestem) interspersed with Quercus virginiana Mill. (Live Oak) and Prosopis
glandulosa Torr. (Honey Mesquite). South Texas brush country, the area of which
has dramatically increased due to overgrazing and fire suppression, is characterized
by Honey Mesquite, Acacia spp. (acacia), and Opuntia spp. (prickly pear).
Exotic grasses occurring in these areas include Cynodon dactylon (L.) Pers.
(Bermudagrass) and Pennisetum ciliare (L.) Link (Buffelgrass). Currently, most
of the breeding range for Texas Botteri’s Sparrows occurs in privately owned
ranches and federal preserves (Laguna Atascosa NWR, Palo Alto National Historical
Site, and tracts of the US Fish and Wildlife Service’s Lower Rio Grande
This study was conducted on the Laureles and Norias divisions of the King
Ranch, near Kingsville, TX. The ranch is 333,866 ha, and research was conducted
in areas of the ranch where the majority of the Texas Botteri’s Sparrows
2013 K.S. Miller, E.M. McCarthy, M.C. Woodin, and K. Withers 389
had been detected within the last 10 years (T. Langschied, King Ranch, Kingsville,
TX, pers. comm.). The Laureles Division, 52 km south of Corpus Christi
on the north shore of Baffin Bay, consists of several habitat types: fallow agricultural
fields, mesquite-thorn scrub, higher and drier grasslands with mesquite
and prickly pear cactus; and extensive lowland Gulf Cordgrass flats. The Norias
Division, 115 km south of Corpus Christi, has stands of cordgrass among
mesquite thickets, prickly pear clusters, and Acacia farnesiana (L.) Willd (Huisache),
but it lacks the extensive open cordgrass flats of Laureles. Two pastures
frequently surveyed in the Norias Division had been root-plowed five to ten
years earlier and were dominated by the exotics Bermudagrass and Buffelgrass,
and these pastures were frequented by resident and migratory birds. Cattle,
horses, and exotic ungulates intermittently graze on all ranch divisions.
We collected data over two field seasons, a pilot season from June to August
of 2004, and a primary season from April to August of 2005. In 2004, we visited
pastures to acquaint ourselves with the birds’ habits, behaviors, nests, and habitat
preferences. In 2005, we visited the same pastures five to six days a week to
search for and monitor nests. Nest-searching was accomplished by observing
parental behaviors (Martin and Geupel 1993), systematic searching, and fortuitous
flushes. We tied flagging to shrubs at least 10 m from the nest to mark the
nest. We revisited the nest every 3–4 days to collect data on clutch size, nestling
age, and nest fate. If a nest remained empty after two successive visits, it was
considered inactive, and we proceeded to collect nest dimensions and microhabitat
Overall reproductive effort
We considered two factors important for reproductive effort: clutch size and
nest success. We followed Webb’s (1985) description of clutch size: the total
number of eggs laid by the female, either when found in laying or incubation, or
inferred from the number of nestlings when found in that stage. We used a series
of photographs from hatch day and subsequent days from a nest where hatch date
was known, together with Webb and Bock’s (1996) descriptions, to estimate the
age of nestlings for which we did not know the hatch date. These ages were used
in calculating Mayfield nest success (Mayfield 1961, 1975).
At each nest, we collected data on primary nest vegetation, nest-cup dimensions,
nest height, and concealment. We identified the primary nesting
vegetation species in which the nest cup was built, and characterized it as exotic
or native. We determined nest-cup dimensions by measuring the diameter
(inside rim to rim) and depth (bottom to the top of the nest cup) in cm. We
also compared the height of the nests in exotic and native grasses. For nests
not directly on the ground, nest height was the distance (cm) from the ground
to the bottom of the nest cup (Burhans 1997).
390 Southeastern Naturalist Vol. 12, No. 2
Nest concealment pertains to the amount of vegetation concealing the nest
from view. We used Olympus digital cameras to take photos of the nest from a
distance of 1 m above the nest and from each cardinal direction. We imported
the photos into Adobe® Photoshop and divided the pixels covered by vegetation
by total pixels to determine percent concealment (Ortega et al. 2003). A “concealment
score” (all five values summed for each nest) and an average percent
concealment were calculated.
Nest site microhabitat
We used the line transect method (Chase 2002) to determine nest site microhabitat,
quantify herbaceous and woody plant species, and determine vegetation
height and density within a 5-m radius surrounding the nest. We placed two
10-m rope line transects, marked in 1-m increments, in random directions with
the nest at the center point of both ropes. We identified plants to species and use
these to assess species richness (the number of species around the nest). At each
meter along the transect, we placed a meter stick perpendicular to the transect
line and measured the height of the vegetation. We determined vegetation density
by recording the number of times the vegetation touched the stick in each
50-cm interval on the stick (Chase 2002). These measurements were averaged
to calculate mean vegetation height. A higher mean number of hits showed
greater vegetative density.
Overall reproductive effort. We defined a successful nest as one where at least
one nestling survived to fledging. We compared clutch size for successful nests to
that of failed nests. Clutch size was not normally distributed, therefore we used
a Mann-Whitney rank sum test.
We calculated overall nest success in two ways: apparent and Mayfield (Mayfield
1961, 1975). To calculate apparent nest success, we divided the number of
successful nests by the total number of nests. We present apparent nesting success
for comparisons to Arizona Botteri’s Sparrow and other grassland species;
however, we acknowledge that it is a biased estimate. Therefore, we also used the
Mayfield method to calculate daily survival rates for each nestling stage (incubation,
hatching, and nestling periods), thus determining the probability that a nest
will survive from incubation to fledging. To determine survival in incubation and
nestling stages, the length of the nesting stage must be known. Using nest data
from both seasons and data from Webb (1985), we used 12 days as the incubation
period and 9 days as the nesting period. All nestlings shared the same hatch day;
therefore, we calculated hatching success but did not factor in a time period for
this stage. Standard deviations for the Mayfield probability were calculated using
methods for a binomial distribution (Ott and Longnecker 2001, Winter 1999).
Nest success was then compared between exotic and native grasslands, using a
Nest characteristics and nest site microhabitat. We wanted to determine if the
type of grassland (exotic vs. native) had any effect on nest characteristics. We
2013 K.S. Miller, E.M. McCarthy, M.C. Woodin, and K. Withers 391
compared nest-cup diameter, depth, height, and concealment, and nest-site characteristics
between exotic and native primary nesting vegetation using Student’s
t-tests (α = 0.05). We used SigmaStat v. 2.03 to conduct statistical analyses. All
values are presented as means ± SD.
We found a total of 50 Texas Botteri’s Sparrow nests, 37 of which were found
in an active nesting stage. Of those, 35 nests provided us with enough information
for Mayfield calculations. Out of 15 nests that were successful, 11 were in exotic
grasslands. Out of the 22 nests that were failures, 13 were in exotic grasslands.
Overall reproductive effort
Clutch size ranged from 1 to 4 eggs or nestlings, with 3 being the mode.
Overall clutch size was 2.97 ± 0.81 (n = 36 nests). There was no significant difference
in clutch size between native (3.00 ± 0.87) and exotic grasses (2.83 ±
0.76) (P = 0.30).
Predators and flooding destroyed 4 of the 8 nests found in 2004, before data
on nest characteristics were collected. The overall apparent nesting success for
2004 and 2005 combined was 41% (n = 37; Table 1). The Mayfield probabilities
for incubation, hatching, and nestling periods, and for survival from incubation to
fledging, are shown for both years (Table 2). Two nests from 2005 were destroyed
before adequate data were obtained for Mayfield calculations. Due to the small
sample size in 2004, we combined the data from both seasons before conducting
statistical analyses. Apparent nest success was unrelated to grassland type (native
vs. exotic: χ2 = 0.794, P > 0.05). There was no significant association in Mayfield
probabilities of survival from incubation to fledging between native (0.41 ± 0.01)
and exotic (0.30 ± 0.02) grasses (P = 0.43, α = 0.05).
The primary cause of nest failure for Texas Botteri’s Sparrows in this study
was predation. We were not able to determine type of predator for 13 of the nests
because there were no signs of predation (e.g., broken egg shells, damaged nest
cups). Solenopsis invicta Buren (Red Imported Fire Ants) also found three nests
and killed the chicks, leaving the nest cup intact. In 2005, one nest that was built
into a Red Imported Fire Ant mound was later abandoned.
Table 1. Nest fate and apparent nesting success for Texas Botteri’s Sparrows on the King Ranch,
southern Texas, 2004–2005A.
Native Exotic Total Native Exotic Total Overall
Fate of nest
Successful (n) 1 2 3 3 9 12 15
Failed (n) 2 3 5 6 10 16 21
Abandoned (n) 0 0 0 1 0 1 1
Total (n) 3 5 8 10 19 29 37
Apparent nesting success 37% 41% 41%
ADue to the small sample size in 2004, we combined the data with 2005 for statistical analyses.
392 Southeastern Naturalist Vol. 12, No. 2
Overall cup diameter averaged 6.9 cm ± 0.6, and overall cup depth averaged
6.6 cm ± 1.0. There was no significant difference in cup diameter between nests
in native (6.89 ± 0.65) and exotic (6.91 ± 0.06) grasses (P = 0.88, α = 0.05). Cup
depth did not differ significantly between native (6.41 ± 1.07) and exotic (6.68 ±
0.91) grasses (P = 0.26, α = 0.05). Only 8 nests, built into Gulf Cordgrass, were
located above the ground. The mean height was 19.3 cm ± 11.8. All nests located
in exotic grasses were built directly on the ground. Statistically, there was no difference
in concealment of nests built in native grasslands (94% ± 4%) compared
to those built in exotic grasslands (96% ± 5%; P = 0.32, α = 0.05); however,
average concealment percentages tended to be lower for nests in native grasses
(n = 17) than for those in exotic grasses (n = 33).
In addition to the 37 nests found during an active nesting stage, we found 13
Texas Botteri’s Sparrows nests that were no longer active, but were of use to us
for nest-site microhabitat analyses. Texas Botteri’s Sparrows nested in both exotic
Table 2. Mayfield probabilities of nest survival for Texas Botteri’s Sparrows on the King Ranch in
southern Texas for 2004 and 2005. This shows the probability (P) of nest survival for each nesting
phase (I = incubation, H = hatching, and N = nestling), and overall nest survival from incubation to
fledging (I to F). Data from both years were combined for overal l Mayfield probabilities.
Year n P I P H P N P I to F
Native 4 0.67 ± 0.01 0.58 ± 0.14 0.34 ± 0.06 0.34 ± 0.05
Exotic 4 1.00 ± 0.00 1.00 ± 0.00 0.39 ± 0.17 0.39 ± 0.17
Total 8 0.86 ± 0.01 0.82 ± 0.06 0.46 ± 0.09 0.45 ± 0.09
Native 11 0.45 ± 0.01 0.36 ± 0.00 0.29 ± 0.04 0.29 ± 0.04
Exotic 16 0.65 ± 0.04 0.64 ± 0.06 0.52 ± 0.06 0.36 ± 0.12
Total 27 0.57 ± 0.03 0.54 ± 0.04 0.43 ± 0.05 0.35 ± 0.09
Native 15 0.50 ± 0.01 0.41 ± 0.03 0.30 ± 0.04 0.30 ± 0.04
Exotic 20 0.72 ± 0.05 0.70 ± 0.08 0.52 ± 0.07 0.42 ± 0.16
Total 35 0.61 ± 0.49 0.57 ± 0.03 0.42 ± 0.06 0.36 ± 0.10
ADue to the small sample size in 2004, we combined the data with 2005 for statistical analyses.
Table 3. Scientific and common names of grass species used as nest support by Texas Botteri’s
Sparrows on the King Ranch, southern Texas, 2004–2005.
Binomial name, common name Exotic or native Number of nests
Cynodon dactylon, Bermudagrass Exotic 27
Spartina spartinae, Gulf Cordgrass Native 8
Dichanthium annulatum, Kleberg Bluestem Exotic 5
Paspalum denticulatum, Longtom Paspalum Native 4
Pennisetum ciliare, Buffelgrass Exotic 3
Paspalum monostachyum, Gulfdune Paspalum Native 2
Setaria parviflora, Knotroot Bristlegrass Native 1
2013 K.S. Miller, E.M. McCarthy, M.C. Woodin, and K. Withers 393
(n = 33) and native (n = 17) grass species (Table 3). Exotic grasses in which nests
were built included Bermudagrass (Fig. 1A), Buffelgrass, and Dichanthium annulatum
(Forssk.) Stapf (Kleberg Bluestem). Nests were also constructed in the
following native grasses: Gulf Cordgrass (Fig. 1B), Paspalum denticulatum Trin.
Figure 1. Digital image of Texas Botteri’s Sparrow nests, indicated by rectangle, on the
King Ranch in southern Texas. Nests were built on the ground in: A. non-native grass
(Bermudagrass), and B. native grass (Gulf Cordgrass).
394 Southeastern Naturalist Vol. 12, No. 2
(Longtom Paspalum), P. monostachyum Vasey (Gulfdune Paspalum), and Setaria
parviflora (Poir.) Kerguélan (Knotroot Bristlegrass).
In addition to grass species, a wide range of herbaceous and woody plants
were found in areas surrounding Texas Botteri’s Sparrow nests. The most common
plant species were Mimosa latidens (Small) B.L .Turner (Karnes Sensitive
Briar), Clematis drummondii Torr. and A. Gray (Texas Virgin’s Bower), and
Honey Mesquite. There was no significant difference (P = 0.16) between plant
species richness in a 5-m radius of nests built in native (4.2 ± 1.4) and exotic
grasses (3.6 ± 1.5). However, there was a tendency for more species to occur in
native grasslands than in exotic grasslands.
There was a significant difference (P < 0.001) between the height of vegetation
surrounding nests built in exotic vegetation and those constructed in
native vegetation. The average height of vegetation surrounding nests built
in native grass was 43.2 cm ± 12.8, whereas the average height of vegetation
surrounding nests built in exotics was 28.7 ± 10.9. The density of vegetation in
a 5-m radius around the primary nesting vegetation was higher in native grasses
(5.4 hits/10 m2 ± 5.2) than in exotic grasses (1.8 hits/10 m2 ± 4.1; P = 0.011).
Overall reproductive effort
Average clutch size was lower for Texas Botteri’s Sparrows than for the
Arizona subspecies (3.41 ± 0.05 SE, n = 101, Jones 2003; 3.3 ± 0.70 SE, n =
23, Webb 1985). However, our clutch size is not unreasonable for a grassland
ground-nesting sparrow. We expect that with a larger sample size our clutch size
would likely be more comparable to the Arizona populations.
Apparent nesting success was also lower for Texas Botteri’s Sparrows than for
Arizona Botteri’s Sparrows (58.3%, n = 24 nests; Webb 1985). We acknowledge
that apparent nest success is a biased estimate; observers are more likely to find
successful nests. Webb (1985) reported apparent nest success for Arizona Botteri’s
Sparrows, and we are reporting apparent nest success for the purposes of
comparison to her research and to other grassland bird studies.
Webb also included in her thesis the information necessary to calculate
Mayfield estimates, allowing us to make comparisons between the populations.
The probability of a nest surviving from incubation to fledging was higher in
Arizona Botteri’s Sparrow populations (0.513). In both Botteri’s Sparrow populations,
there was no significant difference in survival between habitat types.
Research on the Arizona Botteri’s Sparrow population also indicated that the
number of young fledged/adult male and the number of young fledged/plot did
not differ significantly between three habitats (exotic, native, and sacaton habitats;
Within the scope of our study, Texas Botteri’s Sparrows used exotic grasses
more than native grasses as their primary nesting vegetation. We did not measure
availability of exotic and native grass species; however, the majority of nests
2013 K.S. Miller, E.M. McCarthy, M.C. Woodin, and K. Withers 395
were found in an exotic grassland monoculture of Bermudagrass. It is possible
that the Texas Botteri’s Sparrows are following the same expansion trend as the
Arizona subspecies. In Arizona, the exotic Eragrostis sp. (African lovegrass) resembles
sacaton, and the Botteri’s Sparrows have expanded their range with the
expansion of the lovegrass (Bock et al. 1986, Jones and Bock 2005, Webb and
Bock 1996). This change in nesting habitat has also been seen in several other
North American sparrows: Melospiza melodia Wilson (Song Sparrows; Arcese
et al. 2002), Spizella wortheni Ridgway (Worthen’s Sparrows; Behrstock et al.
1994), Peucaea cassinii Woodhouse (Cassin’s Sparrows; Dunning et al. 1999),
and Ammodramus bairdi Audubon (Baird’s Sparrows; Green et al. 2002), which
are increasing their acceptance of cultivated lands that now structurally resemble
prairie (Green et al. 2002).
One reason for the Texas Botteri’s Sparrows’ usage of exotic grasses may
be the structural resemblance of some (e.g., Bermudagrass) to native grasses
(Gulf Cordgrass). On the King Ranch, exotic pastures most heavily populated by
nesting Botteri’s Sparrows had been root-plowed, leaving high and uneven soil
mounds, which have been colonized by Bermudagrass and resembled fields of
tall, dense Gulf Cordgrass. This may have attracted the Botteri’s Sparrows to exotic
grasses; however, long-term effects of nesting in exotic grasses are unknown.
We also acknowledge that nests in exotic grasslands and inland native grasslands
were more visible than those in Gulf Cordgrass.
Nest-cup structure, depth, and diameter were unaffected by primary nesting
vegetation. Texas Botteri’s Sparrows built nests inside or under the bunchgrass
clump, with a tightly woven inner cup and outer nest cup loosely woven into the
host plant (also observed by Webb 1985). Bermudagrass is not normally a bunchgrass,
but it resembled bunchgrass in this study due to root-plowing. These data
support nest-site selection based on vegetative structure rather than plant species
(Jones and Bock 2005).
Nearly 40% of nests built in Bermudagrass were woven around the base of
shrub stems. Reasons for building around shrub stems could vary. It may be the
product of a learned behavior, a response to shrub invasion of the grassland, or it
may result from the structure of the grass cover. Bermudagrass is a much softer,
less erect grass than Gulf Cordgrass, and incorporating a shrub base into the outer
nest cup may increase nest stability or concealment, as well as provide perching
substrate for adults and fledglings. Texas Botteri’s Sparrows build nests on or off
the ground in response to the cover type; in Gulf Cordgrass, nests were built off the
ground, with thinner nest cups, despite the availability of shrubs. Elevated nests
may have improved thermoregulation and concealment, and reduced danger from
flood events in wet years (Wolff 1977). On a larger scale than our sample size, neststructure
alterations in response to a structural component of exotic grasses could
influence nesting success.
Structural components of grass, such as height and density, are used in nestsite
selection by grassland birds (Flanders et al. 2006, Vickery et al. 1995).
396 Southeastern Naturalist Vol. 12, No. 2
Greater mean vegetation height and density in native grass on the King Ranch
suggest that although Texas Botteri’s Sparrows seem to be nesting successfully
in exotic grasses, long-term effects may be negative. Texas Botteri’s Sparrows
are cryptic, and increased vegetative density and height generally afford better
concealment for nests, fledglings, and adults (Jones and Bock 2005). Both Jones
and Bock (2005) and Webb (1985) describe Botteri’s Sparrows using taller and
denser grass clumps for nesting.
As in the case of Arizona Botteri’s Sparrows (Jones and Bock 2005), the
spread of exotic grasses may be providing Texas Botteri’s Sparrows with regained
habitat and increased abundances, thereby contributing to potential
range expansion and population increase. Provided that “grass is sufficiently tall
and dense” (Jones and Bock 2005), Botteri’s Sparrows have been considered
adaptable to “pasturing or diversified agriculture” (Marshall and Clapp 1985).
Increasing “improved” pasture area and disturbed grassland sites may actually
create more available nesting habitat. However, the use of the exotics for nesting
could be detrimental to the King Ranch Botteri’s Sparrow population in the longterm.
Additional research on exotic vegetation (Buffelgrass, Bermudagrass, and
Kleberg Bluestem) in other nesting locations is necessary to determine the impact
on the reproductive success of Texas Botteri’s Sparrow populations in Texas and
to make general inferences about the entire Texas subspecies.
We wish to acknowledge the staff of the United States Geological Survey’s Texas
Gulf Coast Field Research Station, and T. Langschied, coordinator of the South
Texas Wintering Birds Program at Caesar Kleberg Wildlife Research Institute, for their
support throughout the project. The Millicent Quammen Memorial Scholarship, administered
by the Center for Coastal Studies at Texas A & M University in Corpus Christi,
TX, funded our research, and we thank them for this scholarship.
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