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Research Article
Wild Turkey Nest Survival and Nest-Site
Selection in the Presence of Growing-Season
Prescribed Fire
ERIC L. KILBURG,
1
Fisheries, Wildlife, and Conservation Biology, North Carolina State University, Raleigh, NC 27695
CHRISTOPHER E. MOORMAN, Fisheries, Wildlife, and Conservation Biology, North Carolina State University, Raleigh, NC 27695
CHRISTOPHER S. DEPERNO, Fisheries, Wildlife, and Conservation Biology, North Carolina State University, Raleigh, NC 27695
DAVID COBB, North Carolina Wildlife Resources Commission, Raleigh, NC 27606
CRAIG A. HARPER, Department of Forestry, Wildlife, and Fisheries, University of Tennessee, Knoxville, TN 37996
ABSTRACT Concerns about destruction of wild turkey (Meleagris gallopavo) nests traditionally restricted
the application of prescribed-fire to the dormant season in the southeastern United States. Periodic dormant-
season burns were used to open forest understories and increase forage and nesting cover for wild turkeys.
However, much of the Southeast historically burned during late spring and early summer (i.e., growing
season), which tended to decrease understory woody vegetation and promote grasses and forbs, an important
spring and summer food for wild turkeys. Despite the potential benefits of growing-season burns, landscape-
scale application coincident with turkey nesting may destroy nests and reduce or redistribute woody nesting
cover. We determined turkey nest-site selection and nest survival in a landscape managed with frequent
growing-season burns. We monitored radio-tagged female wild turkeys to locate nests and determine nest
survival. We compared vegetation composition and structure at nest sites to random sites within dominant
cover types and calculated the probability of nest destruction as the product of the proportion of wild turkey
nests active and the proportion of the landscape burned. Females selected shrub-dominated lowland ecotones
(a transitional vegetation community between upland pine and bottomland hardwoods) for nesting and
avoided upland pine. Ecotones had greater cover than upland pine and estimated nest survival in lowlands
(60%) was greater than in uplands (10%). Although approximately 20% of the study area was burned
concurrent with nesting activity, only 3.3% of monitored nests were destroyed by fire, and we calculated that
no more than 6% of all turkey nests were exposed to fire annually on our study site. We suggest that growing-
season burns have a minimal direct effect on turkey nest survival but may reduce nesting cover and structural
and compositional heterogeneity in uplands, especially on poor quality soils. A combination of dormant
and growing-season burns may increase nesting cover in uplands, while maintaining open stand conditions.
Ó2014 The Wildlife Society.
KEY WORDS growing-season fire, longleaf pine, Meleagris gallopavo, nest-site selection, nest survival, prescribed fire,
wild turkey.
Prescribed fires traditionally were applied during the
dormant season in southeastern United States forests to
improve habitat conditions for wild turkeys (Meleagris
gallopavo) and avoid fire-related nest destruction and poult
mortality (Stoddard 1936, Brennan et al. 1998, Knapp et al.
2009). Periodic dormant-season burns top-kill woody stems,
stimulate early green-up, and increase the availability of
arthropods selected by presenting female wild turkeys (Sisson
et al. 1990, Palmer et al. 1996, Palmer and Hurst 1998).
Further, dormant-season burns stimulate sprouting of
understory woody stems, which provides nesting cover in
subsequent years (Seiss et al. 1990, Waldrop et al. 1992,
Palmer and Hurst 1998).
Much of the southeastern United States historically burned
primarily during spring and summer, and experimentation
with growing-season fire has produced vegetation conditions
that may benefit wild turkeys (Cox and Widener 2008,
Knapp et al. 2009). Periodic application of early growing-
season fire (May–Jun) in longleaf pine (Pinus palustris)
forests suppresses understory and midstory woody growth
and promotes a more open grass- and forb-dominated
understory than dormant season fire, especially on short (1–3
years) return intervals (Waldrop et al. 1992, Knapp
et al. 2009). Competitive release of herbaceous vegetation
may increase abundance of grass seeds, forbs, and arthropods
important for broods, and increased sight distances may
reduce predation on adults (Hurst 1992, Moore 2006).
Received: 3 June 2013; Accepted: 3 April 2014
Published: 16 July 2014
1
E-mail: ekilburg@gmail.com
The Journal of Wildlife Management 78(6):1033–1039; 2014; DOI: 10.1002/jwmg.751
Kilburg et al. Wild Turkey Nesting and Growing-Season Fire 1033
Although use of early growing-season fire for management
of longleaf pine forests has become common, traditional
concerns about the extent of nest destruction have not been
adequately assessed. Because nest success is commonly the
most influential factor of population growth, it is important
to understand the influence of fire on nest success
(Vanguilder 1992, Roberts and Porter 1996). In one of
the few studies that address fire effects on turkeys, only 9% of
nests over 3 years were destroyed by growing-season fire in
South Carolina, USA. However, the fire return interval (4–5
years) was longer than many longleaf pine forests managed
with prescribed fire, the extent of the site subjected to
growing-season fire was limited (<3%), and the transition to
greater emphasis on growing-season burns had occurred only
recently (Moore et al. 2010). Additionally, because female
wild turkeys often nest in pine stands unburned for more
than 2 years, nesting activity may be focused in fire
management units scheduled to burn, especially under short
fire return intervals (Burk et al. 1990, Sisson et al. 1990).
Because repeated growing-season burns reduce understory
shrubs commonly used by wild turkeys for nest concealment
and promote homogeneous coverage of grasses and forbs,
nest success may be indirectly reduced. Successful nests
often have greater shrub cover, nest concealment, and
structural heterogeneity than unsuccessful nests because
these attributes tend to increase predator search time and
slow the development of search images (Bowman and
Harris 1980, Badyaev 1995, Moore et al. 2010). Addition-
ally, limited shrub cover in uplands that are burned
repeatedly during the growing season may cause females
to nest near riparian areas isolated from fire. We assessed
wild turkey nest survival and nest-site selection in a longleaf
pine ecosystem managed primarily with growing-season
burns implemented on a 3-year return interval. We
hypothesized that landscape-scale application of fire during
the wild turkey nesting season would destroy nests and that
females would nest in vegetation types with greater
concealment than randomly available, primarily in riparian
areas isolated from frequent fire.
STUDY AREA
We studied wild turkey nesting ecology on a 20,000-ha
portion of Fort Bragg Military Reservation in the Sandhills
physiographic region of North Carolina, USA. The Sand-
hills region is characterized by variably deep, well-drained,
sandy soils (dunes; Sorrie et al. 2006), and uplands were xeric
despite an average 120 cm of annual rainfall. Hillside seeps
feed numerous blackwater streams. Forest stands were
burned using prescribed fire every 3 years from January to
September, but primarily during March–June. Since 1989,
growing-season fire was applied on a 3-year return interval to
control woody stem encroachment into the forest midstory in
accordance with management objectives for the endangered
red-cockaded woodpecker (Picoides borealis). Firebreaks and
streams divided the study area into 34-ha (SE ¼0.98) fire
management units. Frequent fire and variable soil moisture
produced many unique vegetation types at Fort Bragg (Sorrie
et al. 2006). Generalized types included bottomland
hardwood (8% land area), ecotone (6%), upland pine
(74%), and non-forested (11%). Bottomland hardwood
included red maple (Acer rubrum), sweetgum (Liquidambar
styraciflua), yellow-poplar (Liriodendron tulipifera), and
blackgum (Nyssa sylvatica) forming closed canopy stands
with sparse understories along permanently flowing streams.
Dense thickets of gallberry (Ilex coriacea), fetterbush (Lyonia
spp.), and greenbrier (Smilax spp.) were common in canopy
gaps and along edges.
Ecotones were lowland pine vegetation located along
ephemeral streams and as a transitional edge between
bottomland hardwood and upland pine types. Ecotones were
associated with hillside seeps, and the width was variable
depending on hydrology and fire history. We estimated land
coverage by ecotone by placing a 20-m buffer (typical ecotone
width) around ephemeral streams and around delineated
bottomland hardwood stands. Longleaf, loblolly (Pinus
taeda), and pond pine (Pinus serotina) were common
overstory species. Understory vegetation was dominated by
giant cane (Arundinaria gigantea), sweet pepperbush (Clethra
alnifolia), huckleberry (Gaylussacia frondosa), gallberry (Ilex
glabra), cinnamon fern (Osmunda cinnamomea), swamp
redbay (Persea palustris), bracken fern (Pteridium aquilinum),
and blueberry (Vaccinium spp.).
Longleaf pine was the dominant overstory species in the
upland pine type with open canopy and an understory of
sparse wiregrass (Aristida stricta), dwarf huckleberry (Gay-
lussacia dumosa), turkey oak (Quercus laevis), and blackjack
oak (Quercus marilandica).
Non-forested vegetation occurred in artillery firing points
and aerial drop zones. Artillery firing points (10–20 ha) were
sparsely vegetated, and 6 aerial drop zones (100–450 ha) were
dominated by a variety of grasses and forbs including
weeping lovegrass (Eragrostis curvula), sericea lespedeza
(Lespedeza cuneata), and blackberry (Rubus spp.). Drop zones
were burned and mowed annually or biennially to reduce
woody vegetation.
Wild turkey abundance increased on Fort Bragg following
restocking efforts between 1998 and 2000. Turkeys were
uncommon on the study area prior to restocking but were
considered abundant during the study (J. Jones, Fort Bragg
Wildlife Division, personal communication). Spring gobbler
harvest increased rapidly from 1 in 1994 to 66 in 2011.
Potential predators of wild turkey nests and adults at Fort
Bragg included American crow (Corvus brachyrhynchos),
bobcat (Lynx rufus), coyote (Canis latrans), raccoon (Procyon
lotor), and gray fox (Urocyon cinereoargenteus).
METHODS
Capture and Monitoring
We captured wild turkeys by rocket net from February to
April 2011 and January to March 2012 (Grubb 1988). In
2011, we fitted 85-g micro global positioning system (GPS)
data loggers (Model G1H271; Sirtrack LTD, Havelock
North, New Zealand) programmed to obtain 4 fixes daily
(every 6 hr) to females. We set the fix rate to optimize
relocation frequency with data logger battery life to ensure
1034 The Journal of Wildlife Management 78(6)
the devices could collect data for >1 year. Data loggers were
equipped with radio transmitters and stored location
coordinates onboard (Guthrie et al. 2011). In 2012, we
fitted females with a combination of micro GPS data loggers
and 80-g very high frequency transmitters (Model A1540;
Advanced Telemetry Systems, Isanti, MN). We aged
females as juveniles or adults by the contour of the rectrices
and molt condition (Pelham and Dickson 1992). We
censored mortalities that occurred within 7 days post-
capture. All capture and handling protocols were approved by
North Carolina State University Animal Care and Use
Committee (#10-149-A).
We located females 3 times weekly by homing (1 Apr–1
Jul). During the nesting season, we flagged sites at a distance
of 30–50 m from the incubating females and monitored the
female’s presence on the nest from outside the flagged
perimeter until the nesting attempt was terminated. We
determined nest fate (the nest was considered successful if
1 egg hatched) from eggshell condition and duration of
incubation (Healy 1992).
Vegetation Sampling
We quantified vegetation characteristics within 20-m-
diameter circular plots centered at the nests and stratified
random points in bottomland hardwood (n¼60), ecotone
(n¼60), and upland pine (n¼75) vegetation types. Access
to aerial drop zones was restricted, so we did not assess
micro-site features within non-forested areas. We randomly
positioned sampling plots within riparian areas at a random
distance from the stream or bottomland hardwood edge to
sample within the ecotone. We delimited the upland edge of
the ecotone as the transition from mesic- to xeric-dominated
understory plant species (Sorrie et al. 2006). Ecotone width
varied greatly but averaged approximately 20 m. We
estimated percent ground cover below 1.2 m with a
20- 50-cm quadrat (Daubenmire 1959) within each plot
at 4 positions along each of 3 transects radiating from plot
center (08, 1208, 2408). We identified vegetation within the
quadrat to genus and grouped vegetation as grass, forb,
woody, and total cover. We measured pine and hardwood
basal area within the plot using a diameter at breast height
(dbh) tape. We estimated percent horizontal cover from 0 to
2 m in 50-cm height categories using a vegetation profile
board (Nudds 1977). We estimated percent horizontal cover
(0–20%, 21–40%, 41–60%, 61–80%, or 81–100%) at each
height category from plot center out to 15 m at 08and 1808in
2011 and in all 4 cardinal directions in 2012 to reduce
variation. We viewed the vegetation profile board from a 1-m
height. We determined distance to nearest stream and
firebreak, the number of years since last burn, and the
number of times burned since 1991 for each nest and random
point using ArcMap 10 (Environmental Systems Research
Institute, Inc., Redlands, CA). Although fire has been
applied in the growing season since 1989, burning activity
was not recorded until 1991, so we used the number of times
burned since 1991.
Data Analysis
We modeled weekly rates at which nests in the study area
were exposed to fire as the product of the proportion of nests
active and the proportion of the study area burned each week.
For example, if 30% of nests were active from 8 to 14 April
(week 2) and 5% of the study area was prescribed burned
during week 2, then 1.5% (0.30 0.05 ¼0.015) of all nests
would be exposed to fire that week. The model assumed nests
were distributed randomly across fire management units (i.e.,
this model assumed time since burn did not influence nest-
site selection) and that forest stands were burned completely.
Because we used the nest monitoring component of the
project to document actual rates of nest destruction from
prescribed fire over 2 nesting seasons, we considered this
landscape-scale modeling approach as a measure of the
potential for fire-induced wild turkey nest mortality where
prescribed burning occurs on frequent intervals (i.e., every 2–
3 years) and during the nesting season (i.e., growing-season
fire). We calculated total nest exposure during the nesting
season for both years as the sum of weekly exposure rates.
We used a geographic information system (GIS) to
determine the percent of each vegetation type on the study
area burned during the nesting season and during the entire
growing season each year of the study (Table 1). We used
these values to demonstrate whether nests located in specific
vegetation types may have been at relatively greater or lesser
risk to fire-induced mortality.
We compared percent horizontal cover and percent ground
cover at random locations among bottomland hardwood,
ecotone, and upland pine vegetation types using analysis of
variance (ANOVA), and we determined pairwise differences
with Tukey’s honestly significant difference test (a¼0.05).
We could not make comparisons to the non-forested
vegetation type because of restricted access to some non-
forested areas.
We modeled landscape-level nest site selection using
logistic regression (R, version 2.15.1, www.r-project.org,
accessed 22 Jun 2012) to obtain the parameters of an
exponential predicting relative nest selection (Manly et al.
Table 1. Overall land cover (%) of bottomland hardwood, ecotone, upland pine, and non-forested vegetation types at Fort Bragg, and percent and average
patch size (ha) of each vegetation type exposed to fire during the wild turkey nesting season (1 Apr–4 Jul) and the vegetation growing season (15 Mar–30
Sep), Fort Bragg, North Carolina, USA, 2011–2012.
Land cover (%)
Nesting season (%) Growing season (%) Patch size (ha) (mean SE)
2011 2012 2011 2012 2011 2012
Bottomland hardwood 8 12 25 14 25 12.4 4.9 25.0 9.8
Ecotone 6 14 24 17 24 0.7 0.1 0.7 0.1
Upland pine 74 18 27 20 27 11.4 0.8 10.8 0.7
Non-forested 11 2 14 11 51 4.8 2.8 24.8 44.1
Kilburg et al. Wild Turkey Nesting and Growing-Season Fire 1035
2002). Using ArcMap, we generated 1,030 random locations
across the study area in bottomland hardwood, ecotone,
upland pine, and non-forested vegetation types. Random
locations represented availability of each vegetation type for
nesting. Nest sites were known use locations (Manly et al.
2002). We generated a 20-m buffer on both sides of
ephemeral streams with a pine overstory and around all
bottomland hardwood stands to estimate availability of
ecotone on the study area. We included only indicator
variables (0 ¼random point; 1 ¼known use location) for
each vegetation type (bottomland hardwood, ecotone, and
upland pine) as covariates in the landscape-level model of
nest site selection using logistic regression. By default, the
fourth vegetation type (non-forested) is indicted in the
model by a 0 for each of the other vegetation types.
We developed 2 models to assess relative nest-site selection
within individual vegetation types (i.e., 1 model to assess
selection in ecotonesand 1 to assess selection in upland pine)by
comparing percent horizontal cover, percent total ground
cover, distance to firebreak,distance to stream, time since burn,
and the number of growing season burns since 1991 at nest
sites and random locations. To limit the number of covariates
in these models, we tested 1 height category from the
vegetation profile board as the percent horizontal cover
covariate in each model. We selected the height category at
which the greatest difference in the mean between used and
random sites occurred. Therefore, we tested percent horizontal
cover at the 0–0.5-m height category in the upland pine model
and at the 1–1.5-m height category in the ecotone model.
We calculated the probability of nest survival using the nest
survival model in Program MARK (www.phidot.org,
accessed 9 Jul 2012; Dinsmore et al. 2002). We exponen-
tiated the daily survival rate by the number of incubation days
for a successful female (i.e., 28 days) to calculate seasonal
survival rates. To determine the most important predictors of
nest survival, we compared 6 a priori models: 1) null; 2) year-
effect; 3) vegetation type; 4) cover; 5) stream; and 6) fire. We
predicted vegetation type would affect nest survival because
understory structure and composition in each vegetation type
largely reflected site hydrology and fire history. We
developed a cover model because greater nest concealment
may reduce detection by predators, and greater nest
concealment is commonly correlated with increased nest
survival (Badyaev 1995, Moore et al. 2010). The cover model
included percent horizontal cover (1–1.5-m height category)
and percent total ground cover. We developed a stream
model because hydrology influences vegetation structure and
composition and likely reflects availability of cover for nest
concealment. The stream model included a single covariate
for distance to stream. We assessed the effect of time since
burn on the probability of nest survival with a fire model.
Fire greatly influences understory vegetation structure and
composition on the study area. We used second-order
Akaike’s Information Criterion (AIC
c
) for model selection
and accepted any model with a DAIC
c
2 (Burnham and
Anderson 2002). We considered parameters in the above
models significant if the 95% confidence interval of the
estimate did not overlap 0.
RESULTS
We captured and radio-marked 65 female wild turkeys in
2011 (6 juveniles, 23 adults) and 2012 (1 juvenile, 35 adults).
Nesting occurred 4 April–4 July in 2011 and 1 April–23 June
in 2012. We located 18 nests in 2011 and 24 nests in 2012,
including 4 renest attempts (1 in 2011 and 3 in 2012). We
removed 12 nests from nest survival modeling because of
observer-induced abandonment (n¼5) or because the nest
was found opportunistically (n¼7) and the unmarked
female could not be monitored. Therefore, we used 30 nests
in nest survival modeling. However, we used all 42 nests in
nest-site selection models.
In 2011 and 2012, 19% and 31% of the study area was
burned during the growing-season and 16% and 22% during
the 14-week nesting season, respectively. The proportion of
the study area burned weekly during the nesting season
ranged from 0% to 2.6% in 2011 and 0% to 6.9% in 2012. We
estimated that 5.4% and 6.1% of wild turkey nests were
exposed to fire during the 2011 and 2012 nesting seasons,
respectively. However, only 1 of 30 (3.3%) monitored nests
failed as a direct result of growing-season burning. The
percentages of each vegetation type exposed to fire during the
growing and nesting seasons were similar (Table 1).
However, bottomland hardwoods often did not burn
completely because of high moisture levels; hence, the
estimated percent exposed, or the percent that was in a
designated burn unit in GIS (Table 1), likely was greater
than the percent that actually burned.
At random locations within vegetation types, percent cover
was greater at all height categories in bottomland hardwood
and ecotone than upland pine (Table 2). Additionally,
percent total ground cover at random locations in ecotone
was greater than bottomland hardwood and upland pine.
Woody vegetation was the primary source of ground cover in
all 3 vegetation types (Table 2). Grass and forb cover was
greater in upland pine than bottomland hardwood and
ecotone vegetation types.
We located wild turkey nests in ecotone (23 nests), upland
pine (9 nests), bottomland hardwood (4 nests), and non-
forested vegetation types (6 nests). Nests were not
distributed randomly; turkeys selected ecotone and avoided
upland pine for nest sites (Table 3). Within the ecotone
vegetation type, nest sites had greater percent horizontal
cover at 1–1.5 m (i.e., taller understory vegetation) and were
closer to streams than random locations (Table 4). Within
upland pine, nest sites had greater percent total ground cover,
were nearer to firebreaks, and were farther from streams than
random locations (Table 5). Because we had too few nests in
bottomland hardwoods and because we did not measure
vegetation structure at random locations in non-forested
areas, we did not analyze nest site selection within those
vegetation types.
Of 30 nests included in survival analyses (n¼15 ecotone,
10 upland pine, 3 bottomland hardwood, 2 non-forested),
predation was the primary cause of nest failure (n¼16)
followed by fire (n¼1) and abandonment (n¼1). All
surviving nests (n¼12) were located in ecotone (n¼9) or
1036 The Journal of Wildlife Management 78(6)
bottomland hardwood (n¼3) vegetation types. The proba-
bility of nest survival given the nest reached incubation was
35% (SE ¼7%) and was similar in 2011 (27%, SE ¼9%) and
2012 (39%, SE ¼9%). Because we located few nests in the
bottomland hardwood and non-forested vegetation types, we
grouped nests into upland (upland pine and non-forested)
and lowland (bottomland hardwood and ecotone) classes in
the vegetation type model. The vegetation type model had
the greatest support and no other models were competitive (i.
e., within 2 DAIC
c
; Table 6). Nest survival was greater in
lowlands (60%, SE ¼10%) than uplands (10%, SE ¼7%).
DISCUSSION
Prescribed burns increasingly are conducted during the early
growing season (Apr–Jun) to promote herbaceous plants and
to match the predominant historical fire season in the
longleaf pine ecosystem (Fill et al. 2012). However, because
these burns occur during the peak of the wild turkey nesting
season, fire-induced nest mortality should be quantified. We
showed that growing-season prescribed fire had minimal
direct effect on wild turkey nest survival because the
probability that a female was actively nesting in a fire
management unit during the time of burning was low.
Although approximately 20% of the study area was burned
during the nesting season each year, only a small portion
(1.4%) of the study area was burned each week, and because
nests are active for 6 weeks of the nesting season
(approximate egg laying and incubation for a successful
nest; Healy 1992), the probability that a nest was active
and located in a burned area was low (<6%). Predation was
the primary source of nest failure (53%) and reduced the
duration of time many nests were active and exposed to fire.
Additionally, predation was greatest in upland vegetation
types that tended to burn thoroughly, so nests that are
destroyed by fire in those areas very likely would otherwise
fail because of predation, suggesting a compensatory effect.
Additionally, nests on Fort Bragg were not located
randomly, and in our study area and elsewhere turkeys
may nest in mesic, lowland vegetation isolated from fire
(Moore et al. 2010). Because bottomland hardwood and
ecotone vegetation types at Fort Bragg often did not burn
thoroughly, nests in those vegetation types (10% and 55%,
respectively) may have been less susceptible to fire. However,
none of the nests we observed in a bottomland hardwood
type were active when fire was applied to the corresponding
fire management unit. Additionally, females that lose a first
nest to fire may renest (Vanguilder 1992). However, the 1
nest destroyed by fire in our study failed in Jun, near the end
of the nesting season, and the female did not renest. Given
the large extent (20%) of our study area that burned annually
during the wild turkey nesting season, nests experienced
a high fire-exposure risk relative to many areas in the
Southeast where the percent of the land base burned is much
less (e.g., Moore et al. 2010). Therefore, the low rate of nest
failure from growing-season fire that we observed at Fort
Bragg suggests that fire-induced mortality rates are as low or
Table 2. Mean and standard error of percent horizontal cover and percent
ground cover at random locations in bottomland hardwood, ecotone, and
upland pine vegetation types at Fort Bragg, North Carolina, USA, 2011–
2012.
Feature
Bottomland
hardwood Ecotone Upland pine
Mean SE Mean SE Mean SE
% Horizontal cover
a
0–0.5 m 80 3A
b
86 1A 653B
0.5–1 m 73 3A 703A 463B
1–1.5 m 66 3A 553A 353B
1.5–2 m 58 4A 433B 283C
% Ground cover
Total cover 41 3B 632A 292C
Woody cover 29 3B 483A 141C
Forb cover 0.4 0.1 B 0.6 0.1 B 10.2 A
Grass cover 1 0.4 B 4 0.8 B 12 1A
a
Horizontal cover was estimated at 4 height categories with a vegetation
profile board from a 1-m height at plot center out to 15 m.
b
Statistical difference among vegetation types for each feature (i.e., row)
using Tukey’s honestly significant difference test. Means with same letter
within a row are not different (a¼0.05).
Table 3. Parameter estimates from a landscape-scale logistic regression
model of wild turkey nest-site selection for 42 nests at Fort Bragg, North
Carolina, USA, 2011–2012.
Parameter
a
b
i
SE P
Intercept 3.09 0.42 0.001
Bottomland hardwood (n¼4) 0.29 0.66 0.66
Ecotone (n¼23) 2.15 0.54 0.001
Upland pine (n¼9) 1.36 0.48 0.01
a
For selection of the non-forested vegetation type (n¼6 nests),
coefficients for bottomland hardwood, ecotone, and upland pine are
0 in the model. Non-forested vegetation type was used as available
relative to all other vegetation types.
Table 4. Parameter estimates for a model of wild turkey nest-site selection
within the ecotone vegetation type for 23 nests at Fort Bragg, North
Carolina, USA, 2011–2012.
Parameter b
i
SE P
Intercept 0.44 1.92 0.82
% Horizontal cover (1–1.5 m) 2.80 1.45 0.05
% Total ground cover 1.53 2.20 0.49
Distance to firebreak 0.01 0.01 0.16
Distance to stream 0.02 0.01 0.02
Time since burned 0.33 0.25 0.20
Growing-season burns 0.26 0.19 0.17
Table 5. Parameter estimates for a model of wild turkey nest-site selection
in the upland pine vegetation type for 9 nests at Fort Bragg, North
Carolina, USA, 2011–2012.
Parameter b
i
SE P
Intercept 6.23 3.48 0.07
% Horizontal cover (0.5–1 m) 3.00 2.40 0.20
% Total ground cover 14.54 4.97 0.003
Distance to firebreak 0.04 0.02 0.04
Distance to stream 0.01 0.003 0.03
Time since burned 0.24 0.42 0.57
Growing-season burns 0.13 0.37 0.72
Kilburg et al. Wild Turkey Nesting and Growing-Season Fire 1037
lower elsewhere in the region where growing-season fire is
applied.
Despite the low risk of fire-induced nest mortality,
growing-season fire may greatly influence nest-site selection
through effects on the distribution of suitable nesting cover.
Female wild turkeys commonly select nest sites with greater
concealment, and understory woody vegetation is often a
component of nesting cover (Hurst and Dickson 1992,
Badyaev 1995, Moore et al. 2010). On our study area, females
selected ecotones and avoided upland pine for nesting.
Ecotones had roughly 20% greater horizontal cover
attributable to greater understory woody vegetation than
the upland pine vegetation type. Repeated growing-season
burns may suppress hardwood midstory and overstory
encroachment from bottomlands into ecotone, and moisture
in ecotones may decrease fire intensity and allow understory
woody vegetation to persist (Glasgow and Matlack 2007,
Knapp et al. 2009). Alternatively, in more xeric uplands,
growing-season burns reduce woody stem densities (Waldrop
et al. 1992, Brockway and Lewis 1997). Although females
selected nest sites in upland pine that had greater percent total
ground cover than was randomly available in the same
vegetation type, total ground cover available in upland pine
was much less than in ecotones. On sites more productive
than the Sandhills, grass and forb cover promoted by
growing-season fire in uplands may provide sufficient nesting
cover (Hurst and Dickson 1992, Palmer et al. 1996). Because
periodic dormant-season burns typically do not reduce
understory woody vegetation as thoroughly as growing-
season burns applied on the same return interval and can
stimulate woody stem sprouting, a combination of dormant
and growing-season prescribed fire may increase suitable
nesting cover in uplands, while maintaining low shrubs along
riparian corridors (Waldrop et al. 1992, Brockway and Lewis
1997, Drewa et al. 2002). Alternatively, increasing growing-
season fire return intervals (to a 4–5-year interval) in some
upland stands would allow woody vegetation to develop and
provide more cover for nesting females.
Changes in vegetation structure resulting from growing-
season fire that affect turkey nest-site selection may influence
nest survival. All nests that hatched were located in lowland
vegetation types, particularly ecotone, where abundant low
shrubs provided greater concealment than understory
vegetation in upland pine. Nest concealment and vegetation
structural heterogeneity around the nest may have decreased
predator search efficiency and reduced predation risk in the
ecotone (Bowman and Harris 1980). However, concealing
cover at the nest was not predictive of nest survival. Rather,
nest survival was most strongly associated with vegetation
type, being greater in lowlands than uplands. Although
concealment parameters were not significant at the microsite
level, cover at the nest-patch scale may have been predictive
of nest survival. In Arkansas, females selected large (80-m
diameter) patches of cover for nesting (Badyaev 1995).
Although females selected greater nest concealment in
ecotone and upland pine than was randomly available in each
vegetation type, respectively, patches of nesting cover in
upland pine may have been more easily searched by predators
because understory vegetation was more open and homoge-
neous as a result of growing-season fire (Bowman and Harris
1980, Waldrop et al. 1992). Establishing greater structural
heterogeneity with periodic dormant-season burns or by
increasing fire return intervals in some upland forest stands
may benefit turkey nest survival.
MANAGEMENT IMPLICATIONS
Growing-season prescribed burning likely is a minor source
of wild turkey nest failure in pine forests of the southeastern
United States where prescribed fire is a commonly used
management tool because the probability that a nest is active
and located in a fire management unit that gets burned is low.
Fires were applied frequently and on fairly large burn units on
Fort Bragg, so we suggest risk of nest destruction from
prescribed burning may be even less elsewhere across the
region where fires are implemented less frequently and on
smaller burn units. Additionally, growing-season fire may
increase nesting cover on the edges of mesic lowlands (i.e.,
ecotones) by suppressing dense thickets of midstory shrubs
and hardwoods and promoting low woody and herbaceous
cover. Conversely, in xeric uplands, growing-season fire may
reduce low woody vegetation often important for nest
concealment and promote a homogeneous groundcover of
grasses and forbs. However, on sites with greater productivity
than the Sandhills, herbaceous vegetation in uplands may
provide sufficient nesting cover. We suggest including
dormant-season fire or longer (4–5-year) growing-season fire
return intervals in some upland forest stands to increase
woody nesting cover and potentially reduce nest predation.
Alternatively, we suggest short (2–3-year) growing-season
fire return intervals may be applied to dense lowland
midstory thickets to establish low shrub conditions consis-
tent with nest sites selected by females and attributed to
greater nest survival.
ACKNOWLEDGMENTS
We thank A. Shultz and J. Jones of the Fort Bragg Wildlife
Branch for providing trapping equipment and field assis-
tance. The North Carolina Wildlife Resources Commission
and U.S. Department of Agriculture Wildlife Services
Table 6. Number of parameters (K), second-order Akaike’s information
criterion (AIC
c
) and Akaike weights (w
i
) of 6 models of wild turkey nest
survival at Fort Bragg, North Carolina, USA, 2011–2012.
Model KAIC
c
DAIC
c
w
i
Vegetation type
a
2 131.33 0.00 0.91
Stream
b
2 137.66 6.34 0.04
Fire
c
2 138.30 6.97 0.03
Null 1 139.18 7.85 0.02
Year-effect
d
2 140.78 9.46 0.01
Cover
e
3 142.55 11.23 0.00
a
Single binomial indicator covariate for nest position: upland (pine or non-
forested) or lowland (ecotone or bottomland hardwood) vegetation types.
b
Single covariate: distance to nearest stream or lake.
c
Single covariate: time since burn.
d
Single binomial indicator covariate for year: 2011 or 2012.
e
Two covariates: percent ground cover and percent horizontal cover from 1
to 1.5 m.
1038 The Journal of Wildlife Management 78(6)
assisted with trapping and provided equipment. Funding for
this research was provided by the U.S. Department of
Defense.
LITERATURE CITED
Badyaev, A. V. 1995. Nesting habitat and nesting success of eastern wild
turkeys in the Arkansas Ozark Highlands. Condor 97:221–232.
Bowman, G. B., and L. D. Harris 1980. Effect of spatial heterogeneity on
ground nest depredation. Journal of Wildlife Management 44:806–813.
Brennan, L. A., R. T. Engstrom, W. E. Palmer, S. M. Hermann, G. A.
Hurst, L. W. Burger, and C. L. Hardy. 1998. Whither wildlife without
fire? Transactions of the North American Wildlife and Natural Resources
Conference 63:402–414.
Brockway, D. G., and C. E. Lewis 1997. Long-term effects of dormant-
season prescribed fire on plant community diversity, structure and
productivity in a longleaf pine wiregrass ecosystem. Forest Ecology and
Management 96:167–183.
Burk, J. D., D. R. Smith, G. A. Hurst, B. D. Leopold, and M. A. Melchiors.
1990. Wild turkey use of loblolly pine plantations for nesting and brood
rearing. Proceedings Annual Conference of Southeastern Association of
Fish and Wildlife Agencies 44:163–170.
Burnham, K. P., and D. R. Anderson 2002. Model selection and multimodel
inference. Second edition. Springer-Verlag, New York, New York, USA.
Cox, J., and B. Widener 2008. Lightning-season burning: friend or foe of
breeding birds? Tall Timbers Research Station Miscellaneous Publication
17. Tall Timbers Research Station and Land Conservancy, Tallahassee,
Florida, USA.
Daubenmire, R. 1959. A canopy-coverage method of vegetation analysis.
Northwest Science 33:43–64.
Dinsmore, S. J., G. C. White, and F. L. Knopf. 2002. Advanced techniques
for modeling avian nest survival. Ecology 83:3476–3488.
Drewa, P. B., W. J. Platt, and E. B. Moser. 2002. Fire effects on resprouting
of shrubs in headwaters of southeastern longleaf pine savannas. Ecology
83:755–767.
Fill, J. M., S. M. Welch, J. L. Waldron, and T. A. Mousseau. 2012. The
reproductive response of an endemic bunchgrass indicates historical timing
of a keystone process. Ecosphere 3:1–12.
Glasgow, L. S., and G. R. Matlack 2007. Prescribed burning and understory
composition in a temperate deciduous forest, Ohio, USA. Forest Ecology
and Management 238:54–64.
Grubb, T. G. 1988. Modifications of the portable rocket-net capture system
to improve performance. USDA Forest Service Rocky Mountain Forest
and, Range Experiment Station, Fort Collins, Colorado, USA.
Guthrie, J. D., M. E. Byrne, J. B. Hardin, C. O. Kochanny, K. L. Skow, R.
T. Snelgrove, M. J. Butler, M. J. Peterson, M. J. Chamberlain, and B. A.
Collier. 2011. Evaluation of a GPS backpack transmitter for wild turkey
research. Journal of Wildlife Management 75:539–547.
Healy, W. M. 1992. Chapter 5. Behavior. Pages 46–65 in J. G. Dickson,
editor. The wild turkey: biology and management. Stackpole Books,
Mechanicsburg, Pennsylvania, USA.
Hurst, G. A. 1992. Foods and feeding. Pages 66–83 in J. G. Dickson, editor.
The wild turkey: biology and management. Stackpole Books, Mechanics-
burg, Pennsylvania, USA.
Hurst, G. A., and J. G. Dickson 1992. Eastern turkey in southern pine-oak
forests. Pages 265–285 in J. G. Dickson, editor. The wild turkey: biology
and management. Stackpole Books, Mechanicsburg, Pennsylvania, USA.
Knapp, E., B. Estes, and C. Skinner. 2009. Ecological effects of prescribed
fire season: a literature review and synthesis for managers. General
Technical Report PSW-GTR-224. U.S. Department of Agriculture
Forest Service, Pacific Southwest Research Station, Albany, California,
USA.
Manly, B. F. J., L. L. McDonald, D. L. Thomas, T. L. McDonald, and W.
P. Erickson. 2002. Resource selection by animals: statistical design and
analysis for field studies. Kluwer Academic, Norwell, Massachusetts, USA.
Moore, W. F. 2006. Survival, nesting success, and habitat selection of wild
turkey populations in the upper Coastal Plain of South Carolina.
Dissertation, Clemson University, Clemson, South Carolina, USA.
Moore, W. F., J. C. Kilgo, W. D. Carlisle, D. C. Guynn, Jr, and J. R. Davis.
2010. Nesting success, nest site characteristics, and survival or wild turkey
hens in South Carolina. Proceedings of the Southeastern Association of
Fish and Wildlife Agencies 64:24–29.
Nudds, T. D. 1977. Quantifying the vegetation structure of wildlife cover.
Wildlife Society Bulletin 5:113–117.
Palmer, W. E., and G. A. Hurst 1998. Prescribed burning effects on wild
turkey hens during preincubation. Tall Timbers Fire Ecology Proceedings
20:102–106.
Palmer, W. E., G. A. Hurst, and B. D. Leopold. 1996. Pre-incubation
habitat use by wild turkey hens in central Mississippi. Proceedings of the
Annual Conference of Southeastern Association of Fish and Wildlife
Agencies 50:417–427.
Pelham, PH., and J. G. Dickson. 1992. Chapter 4. Physical characteristics.
Pages 32–45 in J. G. Dickson, editor. The wild turkey: biology and
management. Stackpole Books, Mechanicsburg, Pennsylvania, USA.
Roberts, S. D., and W. F. Porter 1996. Importance of demographic
parameters to annual changes in wild turkey abundance. Proceedings
National Wild Turkey Symposium 7:15–20.
Seiss, R. S., P. S. Phalen, and G. A. Hurst. 1990. Wild turkey nesting habitat
and success rates. Proceedings National Wild Turkey Symposium 6:18–
24.
Sisson, D. C., D. W. Speake, J. L. Landers, and J. L. Buckner. 1990. Effects
of prescribed burning on wild turkey habitat preference and nest site
selection in South Georgia. Proceedings National Wild Turkey
Symposium 6:44–50.
Sorrie, B. A., J. B. Gray, and P. J. Crutchfield. 2006. The vascular flora of the
longleaf pine ecosystem of Fort Bragg and Weymouth Woods, North
Carolina. Castanea 71:129–161.
Stoddard, H. L. 1936. Relation of burning to timber and wildlife.
Proceedings North American Wildlife Conference 1:399–403.
Vanguilder, L. D. 1992. Population dynamics. Pages 144–164 in J. G.
Dickson, editor. The wild turkey: biology and management. Stackpole
Books, Harrisburg, Pennsylvania, USA.
Waldrop, T. A., D. L. White, and S. M. Jones. 1992. Fire regimes for pine-
grassland communities in the southeastern United States. Forest Ecology
and Management 47:195–210.
Associate Editor: Kerri Vierling.
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