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2011 SOUTHEASTERN NATURALIST 10(4):687–702
Status and Distribution of Breeding Secretive Marshbirds
in the Delta of Arkansas
Michael J. Budd1,3 and David G. Krementz2,*
Abstract - We surveyed the Lower Mississippi Alluvial Valley of Arkansas (“the Delta”)
during the breeding seasons of 2005 and 2006 using the national marshbird monitoring
protocol for secretive marshbirds. We detected and documented breeding by Podilymbus
podiceps (Pied-billed Grebe), Ixobrychus exilis (Least Bittern), Rallus elegans (King
Rail), and Gallinula chloropus (Common Moorhen). We detected but did not document
breeding by Botaurus lentiginosus (American Bittern), Porphyrula martinica (Purple
Gallinule), and Fulica americana (American Coot), all of which have been documented
to breed in the Delta. Our estimated occupancy rates for breeding marshbirds in the
study area ranged from a low of 6% for the King Rail in 2006 to a high of 27% for the
Least Bittern in 2005. The range of these occupancy rates are low and reflect the rarity
of secretive marshbirds in the Delta. Secretive marshbird occupancy rates were higher
in the southern third of the Delta, probably because wetlands were more abundant or of
higher quality there.
Secretive marshbirds include species of the rail, bittern, and grebe families
that primarily inhabit marshes, are dependent upon wetlands for their entire life
cycle, and are difficult to detect. Their generally secretive nature, the endangered
status of several races and populations, and continued loss of habitat warrant an
examination of their status (Eddleman et al. 1988, Johnson et al. 2009, Ribic et
al. 1999). In the Mississippi Alluvial Valley, the Podilymbus podiceps L. (Piedbilled
Grebe) population is possibly decreasing (population trend score [PT] = 4;
Patuxent Wildlife Research Center 2007), and severe deterioration in the future
breeding sustainability is expected (threat to breeding score [TB] = 4, significant
potential threat exists). Ixobrychus exilis Gmelin (Least Bittern) is widespread
but declining (PT = 4), and there are significant potential threats to the breeding
population (TB = 4). Additionally, the US Fish and Wildlife Service (USFWS)
identified the Least Bittern as a species of special concern because they are
relatively rare and we lack basic information on status and trends in most areas
(USFWS 2002). Rallus elegans Audubon (King Rail) has exhibited a decrease in
population size (PT = 5), and a severe deterioration in the future sustainability of
breeding is expected (TB = 4). Many US states consider the King Rail threatened
or of special concern for similar reasons. The population trends for Porphyrula
martinica L. (Purple Gallinule) and Gallinula chloropus L. (Common Moorhen)
1Arkansas Cooperative Fish and Wildlife Research Unit, Department of Biological
Sciences, 1 University of Arkansas, Fayetteville, AR 72701. 2US Geological Survey, Arkansas
Cooperative Fish and Wildlife Research Unit, Department of Biological Sciences,
1 University of Arkansas, Fayetteville, AR 72701. 3Current address - 131 Greenbriar
Circle, Crossett, AR 71635. *Corresponding author. Internet: Krementz@uark.edu.
688 Southeastern Naturalist Vol. 10, No. 4
are largely unknown (PT for both = 3), and some threat to breeding exists (TB =
4 and 3, respectively).
The current status of secretive marshbirds in the Lower Mississippi Alluvial
Valley in Arkansas (“the Delta”) is mostly unknown (K. Rowe, Arkansas Game
and Fish Commission [AGFC], Humphrey, AR, pers. comm.). Meanley (1969)
conducted extensive fieldwork on rails and other wetland-dependent birds in the
Delta during the 1960s and described marshbirds in the vicinity of Stuttgart as
“common”. The Breeding Bird Survey (BBS) has routes in the Delta that have
been run for a number of years (Sauer et al. 2008), but two aspects of the BBS
do not lend themselves well for surveying secretive marshbirds. First, secretive
marshbirds are by nature difficult to detect, and often are only detected using callplayback
methods, which are not part of the BBS protocol (Johnson et al. 2009).
Second, the surveys rely on roads, which typically are not located in or near extensive
marshes where these species occur (Johnson et al. 2009). Evidence of the
difficulty in detecting secretive marshbirds is apparent in the Arkansas wetland
BBS trend analyses for 1966–2006 as no Least Bitterns, Purple Gallinules, or
Common Moorhens were detected. Additionally, only 2 Pied-billed Grebes and
2 King Rails were detected during that time period (Sauer et al. 2008). Within
the Delta, recent breeding season records (AAS 2010) suggest that more secretive
marshbirds are detected in the southern third of the Delta, possibly because
wetlands in that region are more abundant or of higher quality.
The Delta was once part of a vast wetland area comprised of mostly bottomland
hardwoods as well as emergent and submergent wetlands, and prairie. Between the
1950s and the 1970s, this area suffered annual wetland losses exceeding 120,000
ha per year as a result of clearing and conversion to agriculture and aquaculture
facilities (King and Keeland 1999, Wilen and Frayer 1990). It is unknown how this
change in land-use has affected the use of these converted wetlands by secretive
marshbirds, as well as their overall population status in this region.
The objective of our research is to provide an update on the status and distribution
of secretive marshbird populations that breed in the Delta. These estimates will
provide a baseline for future marshbird population monitoring (Johnson et al. 2009).
We conducted our study in the Delta, a region dominated by extensive agriculture
with fragments of remnant bottomland hardwood forest (Fig.1; King et
al. 2006). Wetland habitat types surveyed included bottomland hardwood stands,
Taxodium distichum L. (Bald Cypress) bayous, Cephalanthus occidentalis L.
(Common Buttonbush) swamps, Salix spp. (willow) swamps, Typha spp. (cattail)
marshes, reservoirs with minimal vegetation, and wetlands with a mixture
of habitat types. Sites included a mixture of public and private wetlands.
We divided the Delta into 3 approximately equal regions (north, central,
south) in which we then used stratified random sampling to select survey sites
2011 M.J. Budd and D.G. Krementz 689
(Fig. 1). The 3 strata we used included wetland area, marsh vs. swamp, and forest
area adjacent to the wetland. Wetland area was based on the proportion of a
400-m radius circle, centered at where the observer stood, that was covered in
water, with >50% coverage being a large wetland area (>2.5 ha), 10–50% being
a medium-sized wetland area (0.5–2.5 ha), and <10% being a small wetland area
(<0.5 ha). A marsh is a wetland characterized by herbaceous hydrophytic vegetation,
and a swamp is defined as a wetland containing ≥30% woody vegetation
(Cowardin et al. 1979). Adjacent forest area was based on the proportion of the
400-m radius circle that was covered in woody vegetation ≥6 m in height, with
>50% coverage being a large amount of forested area, 10–50% being a moderate
amount of forested area, and <10% being a minimal amount of forested area.
We randomly selected 50 wetlands per region per year. We selected large
wetland areas containing emergent vegetation non-randomly, as they only existed
at national wildlife refuges (NWRs) and wetland reserve program (WRP) lands.
We selected several sites haphazardly due to logistical problems or because
Figure 1. The Delta of Arkansas (highlighted in gray) subdivided into north, central and
690 Southeastern Naturalist Vol. 10, No. 4
designated wetlands no longer existed. In those instances, we selected the wetlands
closest to the randomly selected wetland.
We conducted three 10-day survey rounds per region, with ≈20 days between
each round of surveys from 16 April–8 July 2005 and from 3 April–21 June 2006,
following the North American Marsh Bird Monitoring Protocol (Conway 2003).
We used 2 observers in 2005 and 3 observers in 2006. We broadcast the breeding
and territorial calls for the following species: Pied-billed Grebe, Least Bittern,
King Rail, Rallus limicola Vieillot (Virginia Rail), Purple Gallinule, and Common
Moorhen. We conducted surveys 30 min before sunrise to 2 hrs after, and from
2 hrs before sunset to 30 min after (Conway 2003). Surveys were not conducted
during heavy rain, heavy fog, or wind speeds ≥19 km/hr. Sites were separated by
≥200 m to avoid double counting individuals (Conway 2003). We trained and
tested observers on the calls of secretive marshbirds before surveying.
In 2005, since we did not have information on detection probabilities for any
of the marshbird species in the Delta, we attempted to make 15 visits to each site.
According to Conway et al. (2004), conducting 15 visits would be the maximum
needed to ensure >90% probability of detecting the species if it is present. During
each 10-day period, we completed 5 surveys per site for a total of 15 surveys
per site in 2005. Based on 2005 results, we determined we only needed to survey
each site 9 times to obtain the same amount of uncertainty (MacKenzie and Royle
2005). Scaling back to 9 visits allowed us to increase the number of sites surveyed.
In 2006, we conducted 4 visits during the first 10-day period, 3 during the second,
and 2 during the third. We put more emphasis on surveying earlier in the season in
case a drought occurred, as in 2005. Birds were only counted if found occupying
the selected site. If birds were located on adjacent wetland units, or encountered
during times of travel, these birds were recorded as opportunistic detections.
We used the maximum number of individuals detected during any one visit
at each site to determine the number of individuals counted overall for each
marshbird species (Paracuellos and Telleria 2004). The total number of individuals
counted overall is not an abundance estimate, but an estimate of the
minimum number of individuals encountered.
We used the program PRESENCE 2.0 to calculate the probability of occupancy
(psi), and in a two-step process, we estimated the probability of detection (p)
as a constant or as a function of observer. We used p for each species to estimate
the probability of a false absence using the formula (1 - p)k, where k equals the
average number of visits conducted (MacKenzie et al. 2006). The sample sizes in
the analysis are smaller than the overall number of sites visited, as we eliminated
sites with fewer than 5 visits in 2005 and fewer than 4 visits in 2006. We chose
these cutoffs, as it was roughly half of the average number of visits per site for
the respective year. We eliminated 4 sites for Pied-billed Grebes from occupancy
estimates as those sites were predominately ditches which Pied-billed Grebes had
not been documented using for breeding (Muller and Storer 1999). Occupancy
2011 M.J. Budd and D.G. Krementz 691
estimates for Common Moorhen and Purple Gallinule were not calculated since
their sample sizes were too small to produce reliable estimates.
In addition to testing for detection being a function of observer, we tested for
a regional effect on occupancy across the Delta based on the observation that
more secretive marshbirds occur in the southern third of the Delta (AAS 2010),
as well as the null model. The regional test included all species in the analysis
under the prediction that densities were highest in the southern region followed
by the central and finally the northern region.
We used Akaike’s information criterion (AIC) corrected for small sample size
(AICc) to select among models. We considered models with ΔAICc values ≤2 to
have strong support (Burnham and Anderson 2002). The detection and occupancy
probability estimates from the null model are reported.
We surveyed 190 sites (80 in 2005, 110 in 2006; Fig. 2). Overall, we surveyed
88 sites in the southern region, 61 in the central region, and 41 in the northern region.
In 2005, 32 sites were on NWRs, 14 on private land, 15 on WRP lands, 16
on wildlife management areas (WMA), 2 on Army Corp of Engineer lands, and 1
was on National Park Service land. In 2006, 26 sites were on NWRs, 63 on private
land, 16 on WRP lands, and 5 were co-managed as a WMA/WRP.
In 2005, 21% of sites were surveyed 15 times (mean = 10.0). In 2005 the Delta
experienced a drought, which resulted in 33 sites completely drying before surveying
them 15 times. In 2006, 86% of sites were surveyed 9 times (mean = 8.45).
In 2005, 54% of sites had ≥1 individual of a particular secretive marshbird species,
and 28% of sites had >1 species. The average number of species per occupied
wetland was 1.9 (SE = 0.16). The maximum number of marshbird species found at
any one site was 5, which occurred at 1 site. In 2006, 46% of sites had ≥1 individual
of a particular secretive marshbird species, and 56% of sites had >1 species. The average
number of species per occupied wetland was 2.3 (SE = 0.21). The maximum
number of marshbird species found at any one site was 6, which occurred at 1 site.
In 2005, the top model selected was the null model with marshbird detection
probability being 0.31 (SE = 0.02), and the occupancy probability being 0.45 (SE
= 0.06). The next most plausible model included region, but the ΔAICc was 2.96.
In 2006, the top model selected included a region effect, with the occupancy being
highest in the southern region followed by the central region and finally the
northern region. The 2006 null model detection probability was 0.44 (SE = 0.03),
and the occupancy probability was 0.32 (SE = 0.05).
Pied-billed Grebe. In 2005, we detected Pied-billed Grebes at 9 sites and
counted 28 individuals (mean count per site = 2.8, SE = 0.59). We opportunistically
detected Pied-billed Grebes at 3 additional sites. In 2006, we detected Piedbilled
Grebes at 20 sites and counted 53 individuals (mean = 2.5, SE = 0.44). We
opportunistically detected Pied-billed Grebes at 10 additional sites. Of the 29 randomly
selected sites occupied by Pied-billed Grebes in 2005 and 2006, 11 were on
federal land, 7 on WRP land, 10 on private land, and 1 on a WMA (Fig. 3).
692 Southeastern Naturalist Vol. 10, No. 4
In 2005, a brood consisting of 3 young was detected at Cache River NWR,
while in 2006, one active nest was detected at the Wallace Trust WRP site, in addition
to a brood, consisting of 3 young, at a different location within the Wallace
Trust WRP site.
In 2005, 9 sites out of 69 were occupied, giving a naïve estimate of 0.13. The
overall detection probably was 0.52 (SE = 0.05), and we found an observer effect.
The occupancy probability was 0.13 (SE = 0.04). The average probability
of a false absence was 0.0006. In 2006, 17 out of 88 sites were occupied, giving
Figure 2. Distribution of sites surveyed for secretive marshbirds in 2005 and 2006 in the
Delta of Arkansas.
2011 M.J. Budd and D.G. Krementz 693
a naïve estimate of 0.20. The overall detection probability estimate was 0.39 (SE
= 0.04), while the occupancy probability was 0.21 (SE = 0.05). The probability
of a false absence was 0.02.
Least Bittern. In 2005, we detected Least Bitterns at 15 sites and counted
20 individuals (mean = 1, SE = 0.21). We opportunistically detected Least Bitterns
at 2 additional sites. In 2006, we detected Least Bitterns at 20 sites and
Figure 3. Distribution of Pied-billed Grebes using detections from randomly selected
sites and opportunistic detections from 2005 and 2006 marshbird surveys in the Delta
694 Southeastern Naturalist Vol. 10, No. 4
counted 37 individuals (mean = 1.9, SE = 0.25). We opportunistically detected
the Least Bittern at 6 additional sites. Of the 25 randomly selected sites occupied
by Least Bitterns for 2005 and 2006, 14 were on federal land, 8 on WRP
land, 2 on private land, and 1 on a WMA (Fig. 4).
Two active nests and two initiated nests were found on 6 June 2006 at the
Wallace Trust WRP site. On 7 June 2006, 4 eggs were found in an active nest on
the Chicot County WRP site, but this nest was found destroyed in late June.
Figure 4. Distribution of Least Bitterns using detections from randomly selected sites and
opportunistic detections from 2005 and 2006 marshbird surveys in the Delta of Arkansas.
2011 M.J. Budd and D.G. Krementz 695
In 2005, Least Bitterns occupied 15 sites giving a naïve estimate of 0.22. The
overall detection probability was 0.16 (SE = 0.04), while the occupancy probability
was 0.27 (SE = 0.06). The probability of a false absence was 0.17. In 2006,
16 out of 88 sites were occupied, giving a naïve estimate of 0.18. The overall
detection probability was 0.58 (SE = 0.05), while the occupancy estimate was
0.18 (SE = 0.04). The probability of a false absence was 0.001.
King Rail. In 2005, we detected the King Rail at 11 sites and counted 24
individuals (mean = 2.18, SE = 0.46). In 2006, we detected the King Rail at 6
sites and counted 18 individuals (mean = 3.0, SE = 0.68). We opportunistically
detected the King Rail at 5 additional sites. Of the 17 randomly selected sites occupied
by the King Rail, 6 were on federal land, 8 were on WRP land, 2 were on
private, and 1 was managed as a WRP/WMA (Fig. 5).
We observed one brood on 6 June 2006 at Hogwallow WRP. There were 5
young with 1 adult. The young were ≈60% of the adult’s size, making them about
30 days old (Meanley 1953). Backdating put the start of incubation at 15 April.
In 2005, King Rails occupied 10 out of 69 sites, giving a naïve estimate of
0.14. The overall detection probability was 0.17 (SE = 0.04), and we found an
observer effect. The occupancy probability was 0.22 (SE = 0.07). The probability
of a false absence was 0.16. In 2006, 5 sites out of 88 were occupied, giving a
naïve estimate of 0.057. The overall detection probability was 0.39 (SE = 0.08),
while the occupancy estimate was 0.06 (SE = 0.03). The probability of a false
absence was 0.02.
Purple Gallinule. In 2005, we detected the Purple Gallinule at 2 sites and
counted 3 individuals (mean = 1.5, SE = 0.5). We did not detect the Purple Gallinule
in 2006, other than 1 opportunistic detection. We only detected the Purple
Gallinule at 2 sites in the southern region in 2005 and 2006 (Fig. 6).
Common Moorhen. In 2005, we detected the Common Moorhen at 2 sites and
counted 6 individuals (mean = 2.8, SE = 2.0). We opportunistically located moorhens
at 2 additional sites. In 2006, we detected the Common Moorhen at 4 sites
and counted 11 individuals (mean = 2.8, SE = 0.48). Of the 6 randomly selected
sites for 2005 and 2006, 2 were on federal land, 1 on WRP land, and 3 on private
land (Fig. 7). Three nests were found at Wallace Trust WRP.
In both years, we detected Botaurus lentiginosus Rackett (American Bittern),
Virginia Rail, Porzana carolina L. (Sora), and Fulica americana Gmelin (American
Coot) during our surveys, but we never recorded any evidence of breeding
by these birds. The last date of detection in either year was 18 May 2006 for
American Bitterns, 7 May 2006 for Virginia Rails, 27 May 2005 for Soras, and
18 May 2006 for American Coots.
We found detection probabilities for secretive marshbirds ranged from a low
of 16% for Least Bitterns in 2005 to a high of 58% for Least Bitterns in 2006.
696 Southeastern Naturalist Vol. 10, No. 4
Detection probabilities for the Pied-billed Grebe were consistently high each
year (39–52%), probably because their loud calls carry well across open water
where they occur; both Least Bittern and King Rail detection probabilities were
lower in 2005 than in 2006. We suspect that the year effect was possibly a result
of observer differences, as the observers used in 2006 had more experience with
marshbirds than those used in 2005. The consequence of the different detection
Figure 5. Distribution of King Rails using detections from randomly selected sites and opportunistic
detections from 2005 and 2006 marshbird surveys in the Delta of Arkansas.
2011 M.J. Budd and D.G. Krementz 697
probabilities among species and within species among years resulted in markedly
different probabilities of false absence. In general, the chances of not detecting
a bird when it was in fact present drops to an acceptable level (<15%) when the
number of survey visits to a site increase (MacKenzie et al. 2006). However, we
found that even with an average of 10 visits per site as in 2005, for both Least
Bittern and King Rail, the false absence probabilities were about 15% because of
Figure 6. Distribution of Purple Gallinules using detections from randomly selected
sites and opportunistic detections from 2005 and 2006 marshbird surveys in the Delta of
698 Southeastern Naturalist Vol. 10, No. 4
their low probabilities of detection. A 15% false absence probability may not be
acceptable depending on the survey goals. We are aware of some marshbird surveys
with usually only one visit per season (Dinsmore et al. 2010), even though
Conway (2008) suggests a minimum number of 3 visits per site per season. If our
detection probabilities for the Least Bittern and King Rail are representative for
Figure 7. Distribution of Common Moorhens using detections from randomly selected
sites and opportunistic detections from 2005 and 2006 marshbird surveys in the Delta
2011 M.J. Budd and D.G. Krementz 699
marshbirds in general, then at 2 or 3 visits per season, the false absence probabilities
will exceed 60%. Such false absence probabilities would not be acceptable,
and not reporting these probabilities would be misleading to the reader.
Status and distribution
We confirmed the breeding of the Pied-billed Grebe, Least Bittern, King Rail,
and Common Moorhen in Arkansas. Nests or broods were observed for all of
these species. We observed a Purple Gallinule carrying nesting material at Arkansas
Post National Park (NP), and AAS records report broods being observed
at this site in previous years (AAS 2010).
Breeding secretive marshbirds are uncommon across the Delta, with the
Purple Gallinule and Common Moorhen being the least common breeding marshbirds
there (James and Neal 1986). We detected Purple Gallinule at 2 sites: at
Arkansas Post NP and the Wrape Plantation unit of Bayou Meto WMA. Only 1
other reported breeding site for the Purple Gallinule in the Delta (Desha County)
has been reported (AAS 2010). Crow (1974) states that the Purple Gallinule is
at the northern limits of its range, and likely expanded its range into Arkansas
as rice farming expanded. We detected Common Moorhens at only 6 randomly
selected sites overall. James and Neal (1986) report scattered nesting records in
the Grand Prairie region of the Delta; however, we failed to detect the Common
Moorhen in this region during our surveys.
As early as the 1920s, the Pied-billed Grebe population in Arkansas was
known to be in danger due to the drainage of wetlands and the demand for grebe
feathers by milliners (Wheeler 1924). Howell (1911) reported the Pied-billed
Grebe as being rare during the nesting season, with only one nesting observation
in the southern region of the Delta. Wheeler (1924) reported that Pied-billed
Grebes nested only in the Sunken Lands in the northeastern portion of the Delta,
and at Wilmot in the southern region. The Arkansas Area Natural Plan indicates
that Pied-billed Grebes have never been a common breeding species due to a lack
of extensive permanent wetland complexes (Crow 1974), a notion also reiterated
in James and Neal (1986). AAS (2010) records, Howell (1911), and Wheeler
(1924) found Pied-billed Grebe more often in the southern and central regions of
the Delta during the breeding season.
We detected Least Bitterns at more sites than expected given their status as
a species of concern. However, the overall occupancy estimates for both years
were never >30%, reflecting that the species is still uncommon in the Delta.
As recently as the 1960s, King Rails were considered common in the Stuttgart
region of Arkansas (Meanley 1969). Rice farms dominate this region, and few
natural wetlands exist there today. We surveyed along the same routes as Meanley
(1953), as well as several rice fields in that area, but failed to detect the King Rail
as well as either the Least Bittern or Purple Gallinule. Our surveys in this area
were not part of the random sampling effort, but more of a focused effort to determine
if King Rails could be found in this area. Changes in agricultural practices
in the Stuttgart area include the dredging of irrigation ditches to keep them clear
of vegetation, the planting of earlier maturing rice varieties, and the mowing of
field edges (F. Lee, University of Arkansas, Rice Research and Extension Center,
700 Southeastern Naturalist Vol. 10, No. 4
Stuttgart, AR, pers. comm.). These changes have resulted in less cover available
for nesting, and apparently have affected not only the King Rail, but also the
Least Bittern and Purple Gallinule, which nested in irrigation ditches around
Stuttgart (Meanley 1969).
Three secretive marshbirds were primarily detected in the southern portion of
the Delta: King Rail, Purple Gallinule, and Common Moorhen. When we tested
across all secretive marshbirds for a regional effect by year, we found evidence
for such an effect during both years, but only in 2006 was the model plausible.
In 2005, the support for the region model was below our cutoff, but only by 1
ΔAICc. We suspect that the southern portion of the Delta had higher occupancy
rates of secretive marshbirds because both the quantity and quality of wetlands
found there were greater than in the two more northern regions.
Of the marshbirds that we detected but did not find evidence of breeding for,
only the American Bittern (James and Neal 1986) and American Coot (AAS
2010, James and Neal 1986) have been documented as breeding in the Delta.
Breeding by both the American Bittern and American Coot is very rare, as both
of these species normally breed farther to the north (Brisbin and Mowbray 2002,
Gibbs et al. 1992).
Our estimated occupancy rates for breeding marshbirds in the Delta ranged
from a low of 6% for the King Rail in 2006 to a high of 27% for Least Bitterns in
2005. We were unable to estimate occupancy rates for both the Purple Gallinule
and Common Moorhen. Even at the high end (27%), these occupancy rates reflect
the rarity of these marshbirds in the Delta. Considering that Meanley (1969) described
King Rails as common in the Delta during the 1960s, the King Rail in the
Delta has clearly undergone declines over the past 50 years. We suspect that the primary
mechanism for the decline in the King Rail, and probably for other secretive
marshbirds in the Delta, is a consequence of loss of wetlands and reduction in quality
of remaining wetlands (Dahl 2006, King and Keeland 1999, Wilen and Frayer
1990). Knowledge of the types of wetlands attractive to secretive marshbirds and
how to manage those wetlands will be necessary to conserve secretive marshbirds
in the Delta. While the types of wetlands and how to manage those wetlands for
secretive marshbirds have been researched (Darrah and Krementz 2009, Rundle
and Fredrickson 1981, Winstead and King 2006), Delta-specific wetland use and
management guidelines are still needed (K. Rowe, pers. comm.).
Funding for this work came from the Arkansas Game and Fish Commission and the
US Geological Survey Arkansas Cooperative Fish and Wildlife Research Unit. A. Claassen,
J. Price, and S. Stake helped collect data, while L. Lewis and K. Rowe assisted with
logistics. We thank all federal, state, and private landowners who allowed us to survey
marshbirds on their properties. S. Lehnen assisted with the analyses. G. Huxel, R. Mc-
New, J. Neal, and N. Winstead made comments on an early draft of this manuscript. Any
use of trade, product, or firm names is for descriptive purposes only and does not imply
endorsement by the US Government. Two anonymous reviewers provided helpful comments
on the manuscript.
2011 M.J. Budd and D.G. Krementz 701
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