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2006 SOUTHEASTERN NATURALIST 5(4):621–636
Woodpecker Use of Forested Wetlands in
Central Peninsular Florida
David L. Leonard, Jr.1,2,* and I. Jack Stout1
Abstract - Habitat preferences for many woodpeckers are poorly known in many
regions of North America. Seven woodpecker species use forested wetlands in
peninsular Florida, yet no study has examined habitat use by woodpeckers in these
forests. From September 1991 to August 1992, we used unlimited-distance point
counts to sample birds at 32 stations in 2 forested wetland types (spring-fed and
blackwater) in central Florida. We documented 1415 visual or aural woodpecker
detections. Melanerpes carolinus (Red-bellied Woodpecker), Picoides pubescens
(Downy Woodpecker), and Dyrocopus pileatus (Pileated Woodpecker) were common,
accounting for 91% of all detections. Overall woodpecker abundance was
greater in spring-fed forests than in blackwater forests. The relative abundance of 4
species was greatest during the fall and winter; this trend likely reflected shifts
between habitats in response to fruit production as well as an influx of migrant
Sphyrapicus varius (Yellow-bellied Sapsuckers). The relative abundance of Redbellied
and Pileated woodpeckers was greatest at sites surrounded by extensive forest
cover. Unlike other studies, we found no relationship between woodpecker abundance
and tree or snag basal area. The presence of Quercus spp. (oaks) also did not
appear important to woodpeckers. Compared to other studies, snag density in the
forests we sampled was high. This may have reduced the importance of snags to
woodpeckers or made detecting relationships difficult. A high density of Sabal
palmetto (sabal palm) may have provided additional foraging and nesting/roosting
sites that further contributed to the lack of correlations between woodpecker detections
and the presence of snags and oaks.
Woodpeckers are conspicuous, relatively sedentary residents of many
forested habitats in North America (Short 1982). By excavating cavities that
provide shelter and nesting sites for other species, woodpeckers play an
important role in forest communities (Bednarz et al. 2004, Bull and Jackson
1995, Martin and Eadie 1999, Martin et al. 2004, Short 1982). Across a wide
range of habitats, woodpecker abundance has been related to snag availability
(Dickson et al. 1983, Shackelford and Conner 1997), forest age
(Shackelford and Conner 1997), and the presence of oaks (Conner et al.
1994). However, few studies have described habitat features that influence
the composition of woodpecker assemblages in the southeastern United
States east of the Mississippi River. In Florida, no study has focused on the
community structure of woodpeckers using forest areas adjacent to rivers.
1Department of Biology, University of Central Florida, Orlando, FL 32816. 2Current
address - State of Hawaii Department of Land and Natural Resources, Division of
Forestry and Wildlife, 1151 Punchbowl Street, Room 325, Honolulu, HI 96813.
*Corresponding author - email@example.com.
622 Southeastern Naturalist Vol. 5, No. 4
Forested wetlands or riparian areas are important components of landscapes.
Due to the juxtaposition of aquatic and terrestrial habitats, forested
wetlands typically harbor greater species diversity of various taxa relative to
the surrounding habitats (Gregory et al. 1991, LaRue et al. 1995). Forested
wetlands have been found to be especially important to birds (Kwit et al.
2004, Murray and Stauffer 1995, Sallabanks et al. 2000), including cavity
nesters (Sedgwick and Knopf 1986, 1990). Fruit or mast is an important
component of the diet of some of the woodpeckers that occupy forested
wetlands in Florida (Beal 1911, but see Boone 1963, Towles 1989). Compared
to other local habitats, Florida hardwood forests support a higher
diversity of fruiting and masting plant species (Ewel 1990, Ewel and
Atmosoedirdjo 1987, Skeate 1987), and thus forested wetlands may provide
critical habitat for certain woodpecker species.
Unlike most non-migratory birds, some woodpecker species show a
preference for large forested tracts (Robbins et al. 1989, but see Bender et al.
1998). In some regions of eastern North America, Melanerpes carolinus
Linnaeus (Red-bellied Woodpeckers) prefer large forested tracts over small
ones (Kilgo et al. 1998, Robbins et al. 1989; but see Keller et al. 1993, Lynch
and Whigham 1984, Noss 1991). Dyrocopus pileatus Linnaeus (Pileated
Woodpeckers) also have been reported to prefer large tracts of undisturbed
forest (Renken and Wiggers 1989, Robbins et al. 1989; but see Keller et al.
1993, Lynch and Whigham 1984). Here we present data on the abundance
and diversity of woodpeckers relative to landscape and vegetative characteristics
in 2 types of forested wetlands in central Florida: those bordering
spring-fed and blackwater rivers.
Study Area and Methods
We selected 19 forested wetland sites bordering 10 tributaries of the St.
Johns River in Orange and Seminole Counties in central Florida based on
availability and access. Five of these tributaries were spring-fed and the
remainder were part of blackwater river systems that drained the surrounding
uplands (see Ewel 1990). Alluvial deposition and scouring during
extensive late spring and summer flooding of blackwater rivers resulted in
the surrounding forests usually having extremely sandy soils as well as an
open understory. In contrast, the spring-fed sites had short hydroperiods,
organic soils, and well-developed vertical vegetation structure (Ewel
1990). Several blackwater forests were embedded in an extensive matrix of
native Pinus spp. (pine) forests.
We used point counts to sample birds at each site (Blondel et al. 1981,
Ralph et al. 1993). To minimize double counting of individual birds, we
separated count stations by at least 160 m (O’Meara 1984). Within this
constraint, we randomly located 32 point-count stations (stations hereafter)
in the 19 sites; large sites (range of site widths: 60–5000 m) had up to 3
stations. No stations fell within ecotones. The primary author sampled each
2006 D.L. Leonard, Jr. and I.J. Strout 623
station twice per month from September 1991 to August 1992. All birds seen
or heard during a 15-minute sampling period were recorded, but only woodpeckers
are included herein. The direction and distance of each bird detected
was noted to minimize double counting. All counts were made within 4
hours of sunrise on mornings without rain or fog, and with minimal wind.
The sampling order of sites was randomized. We acknowledge the limitations
of point-count methodology (e.g., variation in detection probabilities
among species and effects of variation in bird density; Farnsworth et al.
2002, Howell et al. 2004, Norvell et al. 2003). For comparative purposes, we
used the data in Dickinson (1978) and Shackelford and Conner (1997). We
acknowledge that the methods used in these 2 studies were different from
our survey methods; nonetheless, we believe the comparisons of the relative
abundance of woodpeckers across the three studies is useful.
Due to the linear and often continuous character of the sites, we used site
width as a correlate of area (Keller et al. 1993, Kilgo et al. 1998, Smith and
Shaefer 1992, Stauffer and Best 1980, Whitaker and Montevecchi 1999; but
see Groom and Grubb 2001). We determined the width of each site, at each
station, using aerial photographs (1:123 m), and determined the minimum
distance from each station to the edge of the forest. Site width only included
forested habitat (i.e., the width of rivers was not included). We also calculated
the area of the largest continuous forested wetland and the area of the
largest contiguous forest (all cover types) within 1 km of each station.
At each station, we sampled the vegetation in 3 randomly selected 0.04-
ha circular plots (James and Shugart 1970, James et al. 2001), and estimated
the vegetative characteristics of each site using mean values from the circular
plots. We measured the diameter at breast height (dbh) of trees and snags
(i.e., standing dead trees) greater than 5 cm dbh and determined the number
of trees and snags in 5 and 4 size-class categories, respectively. We estimated
canopy coverage using a spherical crown densiometer and canopy
height using a clinometer; estimates were based on 12 and 3 measures,
respectively, per station. We estimated shrub density by counting all stems
(< 5 cm dbh and 1.5 m tall) in two 11.3-m transects transcribing each plot
(James and Shugart 1970). We recorded the number of palms in each circular
plot by species (Sabal palmetto Walter, Serenoa repens Michaux,
Rhapidophyllum hystrix Pursh) and age class (i.e., immature and mature);
age class was based on size. The number of trees, snags, stems, and palms
was averaged across the 3 plots and means were extrapolated to estimates
per ha. We visually estimated the vertical vegetation density using a density
board (MacArthur and MacArthur 1961) at two height categories (0–1.0 m,
1.1–2.0 m). Readings were taken from the 4 cardinal compass directions,
converted to a percentage, and averaged for each station.
We grouped all woodpecker detections into seasons: fall (September,
October, November), winter (December, January, February), spring (March,
April, May), and summer (June, July, August). We present total woodpecker
detections as well as mean (± SD) detection rates. We assumed each
624 Southeastern Naturalist Vol. 5, No. 4
point-count station was independent. Thus, sample sizes were 13 and 19 for
spring-fed and blackwater sites, respectively. We tested all variables
for normality (Kolmogorov-Smirnov Test) prior to analysis. The relative
abundance of the most frequently detected species (Red-bellied Woodpecker,
Pileated Woodpecker, and Picoides pubescens Linnaeus [Downy
Woodpecker]) was normally distributed. However, the variance of species
detected at lower rates (e.g., Colaptes auratus Linnaeus [Northern Flicker])
was high, and results of statistical tests of these species should be viewed
with caution. Despite this, results from parametric and non-parametric tests,
comparing detection rates between sites and across seasons, were similar;
thus, we used t-tests and ANOVAs for these comparisons. For multiple
comparisons, we used Tukey’s HSD test. Several vegetation variables were
not normally distributed, and we used non-parametric statistics to test for
differences in the vegetation between forest types (Mann-Whitney U-tests).
We adjusted significance values to P = 0.01 to minimize Type I errors due
to multiple comparisons. We tested for correlations between woodpecker
abundance and landscape variables using Spearman’s Rank Correlation.
Finally, we used principal component anlaysis (PCA) to examine the underlying
variation in vegetation variables and its potential relationship to
woodpecker detection rates. All analyses were performed using SPSS (version
8.0 for Windows; 1998) and Minitab (Release 12; 1999).
Differences in several of the vegetation variables confirmed that
blackwater sites had a more open understory than those in spring-fed
forests (Table 1). Sites within both forest types had similar basal area and
densities of living trees and snags. However, Fraxinus caroliniana Mill.
(pop ash) was a dominant component of spring-fed sites, but was uncommon
in blackwater sites, and Quercus laurifolia Michaux (laurel oak) was
the dominant tree species in most blackwater sites. Spring-fed sites supported
several tree species (e.g., Tilia Carolina Mill., Ulmus Americana
Linnaeus, Magnolia virginiana Linnaeus), albeit at low densities, that
were for the most part absent from the blackwater sites. The first 4 principle
components explained 61.3% of the variation in the vegetation data.
The loadings from the components indicated that the underlying variation
in the vegetation at each site could be attributed to: (1) basal area of trees
and snags; (2) vertical density of vegetation (e.g., openness); (3) disturbances
likely related to flooding events or tree falls; and (4) stem and saw
palmetto density (Fig. 1). These results corroborate the above findings
(Table 1) and further illustrate the differences in the relative openness of
the 2 forest types.
Spring-fed sites were wider than blackwater sites (1705 ± 2077 m versus
639 ± 1084 m, t = 1.9, 30 df, P = 0.067), and compared to those stations in
blackwater sites, spring-fed sites had more continuous wetland forest cover
(67 ± 25% versus 41 ± 26%, t = 2.9, 30 df, P = 0.009) and more continuous
2006 D.L. Leonard, Jr. and I.J. Strout 625
total forest cover within 1 km (88 ± 21% versus 54 ± 31%, t = 3.5, 30 df,
P= 0.002). Many of the spring-fed sites were in protected areas.
We documented seven woodpecker species (1415 detections), detecting
1.84 ± 1.49 woodpeckers during each 15-minute sampling period (n = 768).
The Red-bellied Woodpecker was the most frequently detected species, and
along with the Downy and Pileated Woodpeckers, accounted for 91% of all
detections (Table 2). Sphyrapicus varius Linnaeus (Yellow-bellied Sapsuckers)
were common only during the winter. Northern Flickers and M.
erythrocephalus Linnaeus (Red-headed Woodpeckers) were restricted to
spring-fed sites, while P. villosus Linnaeus (Hairy Woodpeckers) were
restricted to blackwater sites. The latter 2 species were rarely detected and
only were included in summary analyses and totals. Seasonal abundance of
all species and species richness were higher during fall and winter (F = 16.9,
3 df, P < 0.001) than in spring or summer (F = 15.5, 3 df, P < 0.001; Table 2).
Red-bellied Woodpeckers, Pileated Woodpeckers, Yellow-bellied Sapsuckers,
and Northern Flickers were most abundant in the fall and/or winter
(Table 2). Downy Woodpecker detections were seasonally variable.
Overall woodpecker abundance was greater in spring-fed forests than in
blackwater forests (Table 3). Despite this difference in overall abundance,
the percent composition of the 3 most commonly detected woodpecker
Table 1. Vegetation variables estimated (mean ± SD) from three 0.04-ha circular plots at each
of 32 point count stations in forested wetland study areas in Orange and Seminole counties,
Variable Blackwater (n = 19) Spring-fed (n = 13) P-valueA
Basal area snagsB 1.6 ± 2.1 2.4 ± 3.8 0.35
Basal area of treesB 31.2 ± 12.1 28.3 ± 6.8 0.99
Canopy cover (%) 83.7 ± 3.9 88.2 ± 3.1 < 0.01
Canopy height (m) 23.5 ± 3.3 28.0 ± 3.7 < 0.01
Needle palmC 0.0 ± 0.0 125.2 ± 286.4 < 0.00
Sabal palm (immature)C 364.4 ± 610.4 1338.3 ± 715.7 0.01
Sabal palm (mature)C 294.4 ± 225.2 237.7 ± 146.8 0.60
Saw palmettoC 716.5 ± 693.2 24.3 ± 62.8 < 0.00
Trees 5–8 cm dbhC 126.5 ± 66.6 120.2 ± 89.1 0.08
Trees 9–15 cm dbhC 177.8 ± 80.8 179.6 ± 82.1 0.95
Trees 16–23 cm dbhC 118.9 ± 47.2 109.8 ± 47.0 0.91
Trees 24–38 cm dbhC 113.1 ± 60.4 129.3 ± 63.0 0.17
Trees >39 cm dbhC 78.8 ± 41.4 77.7 ± 32.1 0.92
Number of snagsC 62.1 ± 41.4 39.5 ± 40.0 0.05
Snags 5–16 cm dbhC 27.6 ± 30.5 40.8 ± 25.9 0.06
Snags 17–28 cm dbhC 2.6 ± 4.0 10.1 ± 11.7 0.05
Snags 29–40 cm dbhC 5.1 ± 9.9 6.1 ± 11.4 0.52
Snags > 41 cm dbhC 3.9 ± 6.5 2.6 ± 5.6 0.54
StemsB 638.1 ± 620.5 466.2 ± 358.4 0.74
Vegetation density (0–1 m; %) 26.1 ± 19.9 54.0 ± 15.4 < 0.00
Vegetation density (1–2 m; %) 21.3 ± 14.6 52.1 ± 19.5 < 0.00
Bm2 per ha
CNumber per ha
626 Southeastern Naturalist Vol. 5, No. 4
species was similar. The exception was the Downy Woodpecker. Although
the detection rate of this species was similar between the 2 forest types, it
Figure 1. First four principle components (% variation explained) summarizing the
vegetation characteristics of 32 point-count stations in Orange and Seminole counties,
FL, and scores from each station. Open circles represent forested wetlands along
spring-fed rivers, and closed circles represent forested wetlands along blackwater
2006 D.L. Leonard, Jr. and I.J. Strout 627
comprised a larger percentage of the detections in blackwater forests compared
to spring-fed forests.
Within forest types, seasonal differences in woodpecker detections were
similar to overall seasonal (Table 2) and site (Table 3) differences, with the
Table 2. Total detections for both forest types combined, mean (± SD) seasonal detections, and
mean seasonal totals and species richness of woodpeckers from 768 point counts at 32 stations
in Orange and Seminole Counties, FL, 1991–1992. Means sharing a superscripted letter within
rows are significantly different (P < 0.05; ANOVA, Tukey’s HSD test).
Fall2 Winter Spring Summer
Mean Mean Mean Mean
Species1 Total ± SD Total ± SD Total ± SD Total ± SD Total
RHWO 4 - 1 - 1 - 1 - 1
RBWO 681 0.98AB 189 0.98CD 189 0.83 AC 159 0.75 BD 144
± 0.76 ± 0.82 ± 0.86 ± 0.78
NOFL 32 0.06A 12 0.09 BC 17 0.02 B 3 0.01 AC 1
± 0.24 ± 0.29 ± 0.12 ± 0.07
YBSS 92 0.12 A 22 0.32AB 61 0.05 B 9 - 0
± 0.37 ± 0.51 ± 0.21
DOWP 195 0.34A 66 0.26 50 0.16 A 31 0.43 48
± 0.55 ± 0.54 ± 0.40 ± 0.62
HAWO 4 - 1 - 1 - 1 - 1
PIWO 407 0.67 AB 129 0.58 111 0.44 A 84 0.43 B 83
± 0.63 ± 0.69 ± 0.59 ± 0.62
Total 1415 2.19 A - 2.24 BC - 1.50 B - 1.45AC -
± 1.50 ± 1.70 ± 1.26 ± 1.29
Richness 7 3.44 AB - 4.00 CD - 2.72 AC - 2.75 BD -
± 1.05 ± 0.92 ± 0.89 ± 0.62
1RHWO = Red-headed Woodpecker, RBWO = Red-bellied Woodpecker, NOFL = Northern
Flicker, YBSS = Yellow-bellied Sapsucker, DOWO = Downy Woodpecker, HAWO = Hairy
Woodpecker, PIWO = Pileated Woodpecker; see text for scientific names.
2Fall = September, October, November; Winter = December, January, February; Spring =
March, April, May; Summer = June, July, August.
Table 3. Mean (± SD) and total species detections, and the percentage composition of all
woodpeckers detected at 32 stations in two forest types in Orange and Seminole Counties, FL,
Spring-fed stations (n = 312) Blackwater stations (n = 456)
SpeciesA Mean ± SD Total % Mean ± SD Total % P-valueB
RHWO 0.01 ± 0.14 4 0.5 - 0 - na
RBWO 1.16 ± 0.81 362 48.8 0.70 ± 0.76 319 47.4 < 0.001
NOFL 0.11 ± 0.31 32 4.3 - 0 - na
YBSS 0.15 ± 0.40 46 6.2 0.10 ± 0.32 46 6.8 0.07
DOWO 0.26 ± 0.51 81 10.9 0.25 ± 0.48 114 16.9 0.79
HAWO - 0 - 0.01 ± 0.09 4 0.6 na
PIWO 0.70 ± 0.68 217 29.3 0.42 ± 0.59 190 28.2 < 0.001
Total 2.38 ± 1.58 742 - 1.48 ± 1.30 - < 0.001
ARHWO = Red-headed Woodpecker, RBWO = Red-bellied Woodpecker, NOFL = Northern
Flicker, YBSS = Yellow-bellied Sapsucker, DOWO = Downy Woodpecker, HAWO = Hairy
Woodpecker, PIWO = Pileated Woodpecker.
628 Southeastern Naturalist Vol. 5, No. 4
following exceptions. Red-bellied Woodpecker detections differed seasonally
in blackwater sites (F = 3.13, 3 df, P = 0.026), but Tukey’s HSD test
indicated no significant differences between any 2 seasons. In contrast, Redbellied
Woodpecker detections in spring-fed sites did not differ by season
(F = 1.77, 3 df, P = 0.154). Yellow-bellied Sapsuckers were more abundant
in spring-fed sites (0.41 ± 0.57) during the winter than in blackwater forests
(0.25 ± 0.46; t = 2.10, 190 df, P = 0.037). Finally, Downy Woodpeckers were
more abundant in blackwater forests (0.34 ± 0.55) during the fall than in the
spring (0.15 ± 0.40; F = 3.41, 3 df, P = 0.018).
Differences related to landscape variables
Red-bellied Woodpecker and Northern Flicker detections were more
frequent in sites having an intact upland connection (28.4 ± 5.0 and 2.1 ± 1.9
detections, respectively) versus those with anthropogenic development (e.g.,
houses) in the uplands (17.0 ± 6.9 and 0.3 ± 0.8 detections, respectively; t–
tests, P < 0.05). This pattern did not appear to result from differences in site
width as the width of sites with an undeveloped upland (1082 ± 1860 m) was
similar to those with development in the uplands (1057 ± 1272; t = 0.05, 30
df, P = 0.97). Landscape variables (e.g., site width, distance of station to
edge, percent continuous forested wetland, and percent continuous total
forest site width) were all correlated (rs = 0.37 to 0.65, P < 0.04). Red-bellied
Woodpecker detections were correlated with percent of forest cover for
spring-fed forests (rs = 0.74, P = 0.02), blackwater forests (rs = 0.75, P <
0.001), and for both forest types combined (rs = 0.83, P < 0.001). Pileated
Woodpecker detections were only correlated with percent forest cover when
both forest types were combined (rs = 0.53, P = 0.01). Downy Woodpecker
and Yellow-bellied Sapsucker detections were unrelated to measured landscape
Differences related to vegetation variables
Significant correlations between the previous defined principle components
and woodpecker detections were limited. The detection rate of
Red-bellied Woodpeckers (rs = - 0.62, P < 0.001), Northern Flickers (rs =
-0.70, P < 0.001), and Pileated Woodpeckers (rs = - 0.36, P = 0.045) were
correlated with PC 2. Woodpecker detection rates were not correlated to
PC 1. Detections of the 4 most common species were not related to tree or
snag basal area or to the number of snags per size class (Spearman’s Rank
Correlation, P > 0.05).
Three broad patterns were evident from this study. First, in central
Florida, forests bordering spring-fed rivers supported more woodpeckers
than forests associated with blackwater rivers. The relative proportion of
3 of the 4 most commonly detected woodpeckers, however, was similar
between the 2 forest types. Second, woodpeckers were detected most
2006 D.L. Leonard, Jr. and I.J. Strout 629
frequently in the fall and winter. Third, we found few significant correlations
among the measured landscape or vegetation variables and the
detection rate of woodpeckers. Somewhat unexpected was a lack of correlation
between the basal area or number of snags (in any size class) and
Landscape variables differed between spring-fed and blackwater sites.
Despite this, few landscape variables were correlated with the frequency of
woodpecker detections. The detection rate of Yellow-bellied Sapsuckers and
Downy Woodpeckers was not related to any measured variable. Landscape
variables (e.g., percent forest cover) were related to detections of Redbellied
and Pileated woodpeckers, and therefore these species do appear to
be area-sensitive in central Florida. This relationship, however, may have
been an artifact of habitat preferences unrelated to landscape variables, and
spring-fed sites were wider and had a larger percentage forest cover within 1
km of point-count stations than did blackwater sites. In other regions, Redbellied
and Pileated woodpeckers have been reported to be more abundant in
large versus small forest tracts (Kilgo et al. 1998, Renken and Wiggers 1989,
Robbins et al. 1989). However, these area-abundance relationships may be
restricted to certain geographic regions as these species also have been
reported to be area insensitive (Keller et al. 1993, Lynch and Whigham
1984, Noss 1991).
Although the vegetative characteristics of spring-fed and blackwater
sites differed, few significant relationships were detected between the measured
vegetation variables and woodpecker detections. As indicated by the
PCA analysis of the vegetation data, woodpecker detections were not related
to the variables (i.e., basal area and number of snags) underlying much of the
variation in the vegetative characteristic of the forests in this study. In
contrast, many studies have noted correlations between vegetative variables
(e.g., snag density) and woodpecker abundance (Dickson et al. 1983,
Raphael and White 1984, Renken and Wiggers 1993, Shackelford and
Snags are important to woodpeckers for both foraging and nesting, and
many studies have documented a relationship between snag density and
woodpecker abundance and diversity (Dickson et al. 1983, Evans and
Conner 1979, Raphael and White 1984, Shackelford and Conner 1997,
Styring and bin Hussin 2004). Other studies, especially in the northeastern
United States, have found snags to be a poor predictor of woodpecker
abundance (Gunn and Hagan 2000, Welsh and Capen 1992). In the eastern
Cascades, Haggard and Gaines (2001) reported that woodpecker density was
highest in sites with a medium density of snags. They suggested that preferences
for certain snag species may have resulted in this relationship. In
central Florida, we found no relationship between snags (total number,
number per size class, and basal area) and woodpecker abundance. In the
forests we studied, snag density was high and may have contributed to this
finding. Snag density reported by Shackelford and Conner (1997) was lower
630 Southeastern Naturalist Vol. 5, No. 4
than that documented in this study. In addition, woodpeckers forage on (D.L.
Leonard, pers. observ.) and nest in cavities in sabal palms (Miller 1978,
Stevenson and Anderson 1994). This abundant resource may have partially
mitigated the importance of dicot snags; unfortunately, we did not quantify
the number of dead sabal palms. Alternatively, in cottonwood floodplains,
Sedgewick and Knopf (1986) found that the density of trees with large dead
limbs was a better predictor of cavity density and breeding habitat for cavity
nesters than snag density. We did not quantify density of trees with large
Many studies, across a wide variety of geographic regions and habitats,
have documented the importance of oaks as foraging sites for woodpeckers
(Conner et al. 1994 and references therein). The abundance of woodpeckers
documented in this study suggests that oaks where less important to woodpeckers
than in other regions. In central Florida, oaks (Q. laurifolia, Q.
virginiana Mill., Q. nigra Linnaeus) accounted for 43% of the overstory
basal area in blackwater forests but only 14.5% in spring-fed sites. Conner et
al. (1994) suggested that oak bark, because of its rugosity, may harbor
abundant arthropods. Compared to many oak species, laurel oak has relatively
smooth bark (D.L. Leonard, pers. observ.), and thus may support
fewer or different arthropods compared to other oaks (see Jackson 1979); in
all but one site, laurel oak was the most common oak species. In addition,
sabal palms may have provided alternative foraging sites. For example, we
often observed Red-bellied Woodpeckers gleaning prey from palms.
Although acorns are an important component of the diet of Red-headed
Woodpeckers (Smith et al. 2000), their importance to Red-bellied Woodpeckers
is equivocal (Bent 1939, Boone 1963, Shackelford et al. 2000,
Towles 1989), and they are unimportant in diets of the other species reported
in this study (Bull and Jackson 1995, Moore 1995, Walters et al. 2002). The
fact that woodpeckers were more abundant in spring-fed sites, which had
much lower densities of oaks than blackwater sites, suggests that factors
other than acorn availability influenced woodpecker abundance in the sites
we studied. However, given the high annual variation in acorn production, a
multi-year study may have resulted in a stronger correlation between oak
density and woodpecker detections.
Bird abundance has been linked to the abundance of fruit (Kwit et al.
2004, Skeate 1987), and hardwood forests often have higher fruit biomass
than other habitats (Ewel and Atmosoedirdjo 1987, Kwit et al. 2004). Redbellied
and Pileated woodpeckers, Northern Flickers, and Yellow-bellied
Sapsuckers are seasonally frugivorous (Beal 1911, Bull and Jackson 1995,
Moore 1995, Skeate 1987). In northern Florida hardwood forests, fruit
availability peaks in fall and winter, and the number of frugivorous avian
species is highest during these seasons (Skeate 1987). Thus, the phenology
of fruiting species may have been responsible for the seasonal differences in
detections of woodpeckers. Differences in the species composition and
importance values of trees between the 2 forest types may have contributed
2006 D.L. Leonard, Jr. and I.J. Strout 631
to differences in woodpecker detections. The importance of sabal palm and
saw palmetto fruit to woodpeckers is not well documented (see Bull and
Jackson 1995, Moore 1995, Shackelford et al. 2000); however, based on the
densities of palms in the two forest types, it is unlikely that their fruits were
driving the differences in woodpecker abundance. Sabal palm density was
similar between forest types, and saw palmetto was virtually absent from
spring-fed forests. Spring-fed sites, however, had more fruiting dicot species
(e.g., Nyssa sylvatica Marsh., Morus rubra Linnaeus), albeit at low densities,
than blackwater forests. In addition, differences in the diversity and
density of fruiting vine species (e.g., Smilax sp., Toxiodendron radicans
Linnaeus, Vitis rotundifolia Michaux) may have contributed to the differences
in woodpecker abundance between the forest types, but were not
quantified during this study. The Downy Woodpecker, like most Picoides, is
highly insectivorous (Beal 1911) and was the only species not showing a
clear preference for forest type.
Some aspects of the woodpecker community of central Florida were
similar to that documented in forested wetlands in eastern Texas
(Shackelford and Conner 1997) and in south-central Louisiana (Dickson
1978; Table 4). At all sites, woodpecker detections were highest in the fall
and winter, and Hairy Woodpeckers were rarely detected. In eastern Texas
and central Florida, the Red-bellied Woodpecker was the most common
woodpecker. Differences in woodpecker abundance among the studies also
were noted. In eastern Texas and south-central Louisiana, the relative abundance
of Pileated Woodpeckers was low, while only the Red-bellied
Woodpecker was detected more frequently than the Pileated Woodpecker in
central Florida. Breeding-bird survey data, however, indicates that the
Pileated Woodpecker is more abundant in the regions studied by Dickson
(1978) and Shackelford and Conner (1997) than in peninsular Florida (Bull
and Jackson 1995). The remaining geographic differences are likely the
Table 4. Percent composition of the woodpecker community documented during year-round
surveys in forested wetland communities from three different areas in the southeastern United
SpeciesA Eastern TexasB South-central LouisianaC Central FloridaD
RHWO 9.7 49.6 0.3
RBWO 35.4 16.2 48.1
NOFL 22.9 3.9 2.3
YBSS 6.8 25.9 6.5
DOWO 16.6 - 13.8
HAWO 9.7 1.0 0.3
PIWO 7.1 3.4 28.7
ARHWO = Red-headed Woodpecker, RBWO = Red-bellied Woodpecker, NOFL = Northern
Flicker, YBSS = Yellow-bellied Sapsucker, DOWO = Downy Woodpecker, HAWO = Hairy
Woodpecker, PIWO = Pileated Woodpecker.
BShackelford and Conner 1997.
632 Southeastern Naturalist Vol. 5, No. 4
result of variation in the number of migrant woodpeckers or in the degree of
habitat shifts by resident woodpeckers. In central Florida, a sizeable portion
of seasonal variation appeared to be due to habitat shifts of Red-bellied and
Pileated woodpeckers; the Yellow-bellied Sapsucker was the only migrant
(Robertson and Woolfenden 1992, Stevenson and Anderson 1994).
Wintering Northern Flickers and resident Red-bellied Woodpeckers moving
into bottomland forests in eastern Texas (Shackelford and Conner 1997)
and migrant Red-headed Woodpeckers and Yellow-bellied Sapsuckers in
south-central Louisiana (Dickson 1978) were responsible for much of the
documented seasonal variation in these studies. Depending on their breeding
range, Northern Flickers winter from eastern Texas to central Georgia; individuals
breeding in the Great Plains winter in eastern Texas and Okalahoma
(Moore 1995). During the winter, Red-headed Woodpecker density is high in
the Mississippi River Valley (Bock and Lepthien 1975, Root 1988). Although
the number of wintering Northern Flickers in the panhandle and northern
peninsula of Florida is high, few individuals winter in central peninsula
Florida (Robertson and Woolfenden 1992, Stevenson and Anderson 1994). In
Florida, Red-headed Woodpeckers are generally more common in the summer
than in winter (Stevenson and Anderson 1994), suggesting that some individuals
migrate north in the fall (Smith et al. 2000). Furthermore, in Florida
(Belson 1995, Venables and Collopy 1989) and in many other areas throughout
their range (Smith et al. 2000), Red-headed Woodpeckers are most
common in open forests. This fact likely explains their near absence from the
closed forests surveyed in this study. In peninsular Florida, Yellow-bellied
Sapsucker abundance declines with decreasing latitude (Stevenson and
Anderson 1995). This potentially explains the difference in the number of
sapsuckers detected in Louisiana versus Florida. These observations explain
some of the differences in the relative abundance of woodpeckers between
central Florida and eastern Texas and south-central Louisiana.
Relatively little is known about seasonal movements of Red-bellied and
Pileated woodpeckers. Short (1982) reported that Red-bellied Woodpeckers
are only “slightly migratory,” but may shift to favorable habitats in the
winter (also see Shackelford et al. 2000). This corroborates the findings of
Shackelford and Conner (1997) as well as our findings, although in southcentral
Florida, banded Red-bellied Woodpeckers remained on nesting
territories in Pinus palustris Mill. (longleaf pine) flatwoods throughout the
year (D.L. Leonard, unpubl. data). Pileated Woodpeckers may wander
seasonally, and there is some evidence of limited migration (Bull and
Similar to the findings from other regions (Dickson 1978, Kilham 1976,
Shackelford and Conner 1997), our results indicate that forested wetlands
are important to the woodpeckers inhabiting central Florida, especially in
the fall and winter. Spring-fed sites supported more species, and a greater
abundance of woodpeckers than blackwater forested wetlands, suggesting a
preference for these forests. Landscape features were responsible for little of
2006 D.L. Leonard, Jr. and I.J. Strout 633
these differences. We did identify correlations between some vegetative
variables and woodpecker detections; however, these correlations often differed
from other studies. Differences between central Florida forested
wetlands and habitats in other regions (e.g., high snag density, presence of
sabal palms) likely contributed to this disparity. Autecological studies focusing
on substrate use and seasonal movement patterns are required to
further understand the habitat use and abundance patterns of woodpeckers
using forested wetlands in central Florida.
We thank R. Conner, H. Freifeld, D. Richardson, D. Swan, and two anonymous
reviewers for their careful and insightful comments that improved earlier drafts of
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