survive burn events, while the aboveground growth points of woody plants can lead to .... conditions, and proximity to power lines and private property. .... Wood Duck ..... ground litter coverage, more openings for sunlight to reach emerging ...
EFFECTS OF PRESCRIBED BURNING ON GRASSLAND AVIFAUNA AT RIVERLANDS MIGRATORY BIRD SANCTUARY Travis J. Wood, Richard L. Essner, Jr., Peter R. Minchin SOUTHERN ILLINOIS UNIVERSITY EDWARDSVILLE Abstract North American grassland habitat has nearly disappeared since European settlement, with much of the remaining habitat severely degraded. As suitable habitat has vanished, many native grassland bird species have experienced pronounced population declines. Despite the widespread use of prescribed fire as a management tool to maintain grassland habitat, little is known about the definitive impacts of frequent burning on grassland bird populations. We examined the impact of prescribed fire on the vegetative structure and bird community at Riverlands Migratory Bird Sanctuary in West Alton, Missouri. Bird abundance and habitat characteristics were measured at 81 sampling plots, with 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Plots burned 2-4 years prior to sampling exhibited the greatest total species richness. Mean species richness, Shannon’s diversity index, and Hill’s diversity index did not differ among burn groups. Ten species had significant indicator values for one of three burn groups and six species had estimated densities that differed based on burn group. Forb coverage, woody vegetation coverage, ground litter coverage, ground litter depth, distance to the nearest water source and distance to nearest edge differed among burn groups. The presence of woody vegetation was associated with high levels of structural heterogeneity within those plots burned 2-4 years prior to sampling. These areas supported species associated with both disturbed and undisturbed habitat. Introduction Prior to European settlement, the grasslands of North America, ranging from southern Manitoba to Texas, covered an estimated 162 million ha of land (Knopf 1994). These extensive grasslands consisted of shortgrass prairie in the west, mixed-grass prairie in the center, and tallgrass prairie in the east (Anderson 1990). North America has experienced an estimated 99.9% loss of native grassland habitat, resulting primarily from the conversion of fertile grasslands to agricultural fields (Samson and Knopf 1996). Historically, tallgrass bottomland prairies were an important component of the Mississippi and Missouri River confluence landscape, comprising ~29% of pre-settlement vegetation in the American Bottom Ecoregion (Black et al. 2009). The American Bottoms consists of the Mississippi River corridor, extending from the confluence with the Kaskaskia River to the Melvin Price Locks and Dam in Alton, Illinois. This ecoregion was historically characterized by vast stretches of bottomland prairie, bordered by oak and hickory timberlands along the riverbanks and upland hillsides (Nelson et al. 2003). The historical wet, wet-mesic, and mesic prairies of the Mississippi River floodplain have been nearly eliminated and replaced with row crops consisting primarily of corn, soybeans, and wheat to take advantage of the nutrient-rich sediments found in the floodplain soils (Soil Conservation Service 1977). Today less than 4% of pre-settlement tallgrass prairie remains in North America, with much of the remaining grasslands severely degraded due to fire suppression, overgrazing, and habitat fragmentation (Steinaur and Collins 1996). As suitable grassland habitat has vanished, many native grassland bird species have experienced pronounced population declines that exceed those of any other group of North American birds (Knopf 1994; Herkert 1995). Grassland and shrubland-dependent bird species have declined in eastern and Polymath: An Interdisciplinary Arts and Sciences Journal, Vol. 3, No. 1, Winter 2013
Effects of Prescribed Burning on Grassland Avifauna central North America, with greater numbers of species designated as endangered or threatened compared to their woodland counterparts (Askins 1993). Fifty-five grassland bird species have been listed as threatened or endangered in the United States (Samson and Knopf 1996). Forty-eight percent of grassland bird species are of conservation concern, with population declines of species, such as the Eastern Meadowlark (Sturnella magna) and Dickcissel (Spiza americana), having occurred throughout their entire breeding range (Askins et al. 2007; North American Bird Conservation Initiative 2011). Of those species of grassland and shrubland birds experiencing population declines in the Midwest region of the United States, Henslow’s Sparrow (Ammodramus henslowii) is of greatest conservation concern, followed by Dickcissel, Bobolink (Dolichonyx oryzivorus), Sedge Wren (Cistothorus platensis), Bell’s Vireo (Vireo bellii), Grasshopper Sparrow (Ammodramus savannarum), Upland Sandpiper (Bartramia longicauda), Field Sparrow (Spizella pusilla), Clay-colored Sparrow (Spizella pallida), and Loggerhead Shrike (Lanius ludovicianus; Herkert et al. 1996). Grassland ecosystems evolved in the presence of periodic disturbances, caused primarily by fire and grazing (Wright and Bailey 1982). Naturally-occurring fires are an important component of the creation and maintenance of tallgrass prairies in North America, with an average burn cycle of 2-5 years (Steinauer and Collins 1996). While fires occurred naturally due to lightning strikes, it has been estimated that up to half of the historical fires in tallgrass prairies were due to land use by Native Americans (Higgins 1986). Disturbances such as lightning strike fires and those fires set by Native Americans contributed to a mosaic of different vegetation communities in the American Bottoms Ecoregion (Nelson et al. 2003). Fires increase coverage of fire-tolerant grasses at the expense of firesensitive woody vegetation (Anderson 1990). Belowground growth points allow herbaceous plants to survive burn events, while the aboveground growth points of woody plants can lead to death or topkill following a burn event (Anderson 1990). Fire has been shown to increase vegetation height and density, while decreasing ground litter in tallgrass prairies (Schramm et al. 1986). Fires can also increase the abundance of insects, including grasshoppers and beetles that grassland birds utilize as a primary food source during the breeding season (Swengel 2001). Fire suppression within contemporary grasslands has led to an increase in woody vegetation coverage throughout the tallgrass prairie region of North America (Briggs et al. 2005). Increases in woody vegetation edges within grassland systems reduce grassland bird abundance and increase rates of nest predation (Johnson and Temple 1990; Winter et al. 2000). Exposure to woody vegetation edge habitat has also been linked to increased rates of nest parasitism by Brown-headed Cowbirds (Molothrus ater; Johnson and Temple 1990; Patten et al. 2006). As a result of the degradation of native grasslands and the subsequent sharp declines of associated bird populations, the effective management of grasslands has become increasingly important. Prescribed fire has become a common management tool to simulate natural disturbances in order to maintain grass-dominated habitat and prevent the invasion of woody vegetation. Despite the widespread use of prescribed burning as a management tool, little is known about the definitive impacts of frequent burning on grassland or shrubland bird species that utilize grassland habitats (Herkert 1994a). Studies that have examined grassland bird response to single burn events (e.g., Pylypec 1991; Reynolds and Krausman 1998; Naugle et al. 2000) have shown a pattern of reduced bird abundance and species diversity in areas surveyed immediately post-fire, but these studies do not capture the long-term impact of burn history on declining grassland bird populations. Johnson (1997) and Madden et al. (1999) found reduced bird abundance immediately following a burn event, but no long-term effect on bird abundance. Other studies that have focused on short and long-term burn histories have shown conflicting results for individual grassland bird species (e.g., Sedge Wrens; Schramm et al. 1986; Herkert 1994a; Delisle and Savidge 1997). The response of grassland birds to prescribed fire is due in large part to the structural vegetation changes that result from disturbance events (Whelan 1995). Disturbance events can increase the level of structural heterogeneity within 20
Polymath: An Interdisciplinary Arts and Sciences Journal grassland landscapes, which in turn may lead to increased species diversity (Fuhlendorf and Engle 2001). Increases in species diversity in heterogeneous landscapes result from the ability for species with different habitat requirements to utilize the same habitat area (Fuhlendorf and Engle 2001). Effective management of grasslands depends on understanding the interconnected impacts of fire-related disturbance on the tallgrass prairie community. The goal of this study was to examine the effects of the long-term use of prescribed fire on grassland birds and prairie vegetation in order to inform future management decisions. We hypothesize that species diversity and mean bird densities will differ based on time since last burn, with the highest levels of bird abundance and diversity expected within those plots in the intermediate burn group (burned 2-4 years prior to sampling). Recently burned plots (0-1 year prior to sampling) are expected to contain little woody vegetation coverage, which could reduce species diversity by not providing the habitat requirements of species dependent on woody vegetation. Plots burned 2-4 years prior to sampling are expected to contain intermediate levels of woody vegetation coverage, forb coverage, and grass coverage, which in turn have the potential to meet the habitat requirements of a variety of specialist and generalist grassland species. Areas burned ≥5 years prior to sampling are expected to contain the greatest amount of woody vegetation coverage, which may reduce species diversity by not providing the suitable habitat for species that are sensitive to woody vegetation (Johnson and Temple 1990). Methods Study Area Riverlands Migratory Bird Sanctuary (RMBS) encompasses 1498 ha of river floodplain habitat, including 486 ha dedicated to wetland and prairie restoration. Located in West Alton, Missouri (Latitude 38.86847°, Longitude -90.18585°) directly adjacent to the Mississippi River, RMBS is a stopover site along the Mississippi Flyway migratory bird route. It is located near the confluence of the Mississippi and Missouri Rivers within the American Bottom Ecoregion. The construction of the Melvin Price Locks and Dam, beginning in 1978, resulted in increases in groundwater levels beneath adjacent agricultural fields. The rising groundwater levels led to the degradation of agricultural fields, which were purchased by the United States Army Corps of Engineers (USACE). The degraded fields became infested with Musk Thistle (Carduss nutan) and the USACE developed a management plan focused on the reduction and control of invasive plant populations by reestablishing permanent vegetation cover. In addition to invasive species control, the objective of planting permanent, native vegetation was to recover the Environmental Demonstration Area to pre-settlement conditions consisting of a bottomland prairie/wetland complex within the Mississippi River floodplain. Beginning in 1989 the USACE converted 323 ha of cropland to wet, wet-mesic, and mesic prairie. Prairies were planted in separate mixes of native warm-season grasses associated with these soil types, including Big Bluestem (Andropogon gerardii), Switchgrass (Panicum virgatum), Eastern Gamagrass (Tripsacum dactyloids), Indian Grass (Sorghastrum nutans), and Prairie Cordgrass (Spartina pectinata). The mesic prairie plantings occurred in areas characterized by well-drained soils; whereas, wet-mesic and wet prairie plantings occurred in areas characterized by relatively poorly-drained soils. Cool season grasses, such as Timothy (Phleum pretense) and Redtop (Tridens flavus), were planted as firebreaks. In addition to the 323 ha of restored bottomland prairie, 122 ha of RMBS consists of emergent marshes that are connected by gravity drainage ditches that allow for the manipulation of water levels throughout the sanctuary. Since 1999 USACE has managed the 486 ha of restored prairie and wetland habitats through the use of prescribed fire. RMBS is divided into 20 management units, which range in area from 0.7 ha to 11.5 ha. The USACE uses a variety of management tools to manipulate habitat within each management unit, including water level manipulations, prescribed fire, mechanical removal of woody vegetation, and mowing. Managers at RMBS utilize spring prescribed burnings to promote the growth of native grasses and forbs and to reduce existing and future woody vegetation cover, ground litter, and dead vegetation (McGuire pers. comm. 2011). The USACE burn plan calls for each 21
Effects of Prescribed Burning on Grassland Avifauna management unit to be burned on a three year rotation to ensure that all potential avian nesting sites are not burned within the same year. Burns are conducted in early March so that nesting activities are not impacted by fire and are contingent upon a multitude of factors including, funding, weather conditions, and proximity to power lines and private property. These factors result in some areas remaining unburned for longer periods than what is recommended in the burn plan. Study Design Bird abundance and vegetation characteristics were measured at 105 randomly-selected sampling plots in the summer and fall of 2011 by a single observer. Plots were located across three separate burn categories, each encompassing approximately 120 ha, based upon time since last burn. Burn category groups consisted of 35 plots burned 0-1 year prior to sampling (121 ha), 35 plots burned 2-4 years prior to sampling (113 ha), and 35 plots burned ≥ 5 years prior to sampling (124 ha; Figure 1). The number of plots used in analyses was subsequently reduced to n=81 due to mowing disturbance (described below). Sampling plots were randomly selected using Hawth’s Analysis Tools for ArcGIS Desktop 9.3 (ESRI 2008) with the condition that all points were separated by at least 100 m to allow for statistical independence and were at least 25 m from all roadways, engineered waterways, bodies of water, power-lines, mowing strips, agricultural fields, and forested areas to minimize associated edge effects. A GPS receiver (Garmin GPSMAP 62) with a precision of 2 m under survey conditions was used to locate each sampling plot. A 1.5-m long piece of 2-cm diameter PVC pipe was driven into the ground in the center of each plot to aid in locating the plots during each sampling event. Two strips of orange-colored duct tape were applied approximately 2.5 cm from the top of each marker and identifying plot information was inscribed between the colored strips. Bird Density Sampling Bird density was estimated using 50-m fixed-radius point counts (Hutto et al. 1986). Each of the 105 sampling plots was surveyed three times during 6 June – 23 August 2011, with the first round of sampling occurring 6 June – 7 July, the second occurring 8 July – 29 July, and the third occurring 4 August – 23 August. Each sampling event began with a one-minute warm-up period to allow for the surrounding wildlife to acclimate to the observer's presence, followed by a 10-minute sampling period, recording all birds seen or heard. We noted whether observed birds were located within or outside of the 50-m fixed-radius and only birds found within the radius were used in statistical analyses. A laser rangefinder (Nikon ProStaff 550) was used to determine the extent of the 50-m fixed-radius boundary during each sampling event to reduce observer error. Point counts were conducted beginning one half hour before sunrise until three hours after sunrise, except on mornings when rain, fog, or excessive wind limited the detection of birds. During each sampling period binoculars (Nikon Monarch ATB) were used for visual identification of birds and a digital voice recorder (Olympus WS-700M) was used to record the entire 10-minute sampling event for subsequent audio identification in the lab by comparison with known vocalizations. Densities per hectare for each species in each plot were calculated by dividing the mean number of individuals counted over the three samplings by the area of the plot (0.79 ha). Vegetation Sampling Vegetation characteristics were measured at each of the 105 sampling points during 12 August – 5 November 2011. Ten 1-m² quadrats were sampled per plot at 10-m intervals along a transect line running the length of the 100-m plot diameter and bisecting the plot center. Each transect line was oriented at a randomly-selected compass bearing, that was generated using a random number generator (Microsoft Office Excel 2007) and a 5-m buffer separated quadrats from the center and outer edges of each plot. At each 1-m² quadrat a Braun-Blanquet cover class value was assigned to 22
Polymath: An Interdisciplinary Arts and Sciences Journal
Figure 1. Location of the 50-m fixed-radius plots (n=105). Triangles signify plots that were mowed, while black dots signify plots that were not mowed and were included in the statistical analysis (n=81). estimate percent coverage of forbs, woody vegetation, grasses, ground litter, and total vegetation (Table 1; Braun-Blanquet 1965). The median cover class values were summed within each plot and averaged within each burn category group to obtain mean habitat variable measurements. Litter depth (cm) and maximum vegetation height (cm) were measured directly at each quadrat. The distance to the nearest edge (m) and to the nearest water source (m) for each plot was measured using the measure tool in ArcGIS Desktop 9.3 (ESRI 2008). It was assumed that each transect line along the 100-m plot diameter was representative of the entire survey plot in which the birds were surveyed (Scott et al. 2002). Following the first sampling event and prior to the second sampling event 17/35 plots burned ≥5 years prior to sampling and 7/35 plots burned 2-4 years prior to sampling were mowed by the USACE in June 2011 as part of their grassland management strategy (Figure 1). Due to this human disturbance event all bird abundance and habitat variable measurements recorded within mowed plots were omitted from the statistical analyses and summary tables and figures. Following this decision the study design consisted of 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Statistical Analysis The null hypothesis that there were no differences in mean species richness, mean density estimates, and mean habitat variable measurements among burn category groups was tested using one-way analysis of variance (ANOVA; Hintze 2007). 23
Effects of Prescribed Burning on Grassland Avifauna Table 1: Braun-Blanquet cover classes, the percent coverage ranges that the cover classes represent, and the midpoints of the percent coverage ranges. Cover Class % Coverage Range % Coverage Midpoint 1 99 99.5
Species diversity within the burn category groups was compared by measuring total species richness across all plots (gamma richness), mean species richness, and Shannon’s and Hill’s diversity indices using Primer 6 (Clarke and Gorley 2008). Total species richness (S; number of different species) was summed within each burn category group among all three bird sampling events. Mean species richness ( S ; average number of species) was calculated by summing the total species richness within each sampling plot and obtaining an average value for each burn category group. In addition to utilizing ANOVA to test for differences among burn groups based on mean species richness, species-area curves (PC-ORD 5) were used to compare the relationship between species richness and area for each burn category group (McCune and Mefford 2006). Shannon’s diversity index (H’), which accounts for both species richness and evenness, was calculated using the following equation: H’ = -Σpi log (pi). In this equation pi represents abundance of each species represented as a proportion of the total abundance. Hill’s diversity index (N1), which is the exponential log of Shannon’s diversity index, accounts for species richness independent of the log base. This fractional richness produces higher values as species richness and evenness increase. The following equation was used to calculate Hill’s diversity index (N1): N1 = e(H’) Indicator species analysis (ISA, PC-ORD 5; Dufrene and Legendre 1997; McCune and Mefford 2006) was used to determine which species possessed significant indicator values for a particular burn category group based on the time since last burn. Indicator species analysis combines relative abundance values for a particular species with that species’ relative frequency of occurrence within each group. A maximum indicator value is observed when all the individuals of a species are found in only a single group and that species occurs within all of the sites found in that group (Dufrene and Legendre 1997). A Monte-Carlo randomization procedure was used to evaluate the statistical significance of species indicator values. A liberal P-value of 0.15 was used for the ISA due to the exploratory nature of the analysis. Results Species Diversity Thirty-three different bird species were observed within the 81 sampling plots (Table 2), with an additional 23 species recorded outside of the 50-m fixed-radius plots (Table 3). Twenty-six species were observed within plots burned 2-4 years prior to sampling, 21 species within plots burned 0-1 year prior to sampling, and 19 species within plots burned ≥5 years prior to sampling (Table 4). Oneway ANOVA indicated that average species richness per sampling plot did not differ among burn category groups (Table 4). Based on the species-area curves (Figure 2) species richness at the 10 ha 24
Polymath: An Interdisciplinary Arts and Sciences Journal Table 2. Bird species observed within 50-m fixed-radius plots (n=81), including 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Common Name Species Red-winged Blackbird Mallard Ruby-throated Hummingbird Great Blue Heron Northern Cardinal American Goldfinch Killdeer Marsh Wren Sedge Wren Northern Bobwhite Blue Jay Gray Catbird Willow Flycatcher Common Yellowthroat Baltimore Oriole Orchard Oriole Least Bittern Song Sparrow Blue Grosbeak Indigo Bunting Cliff Swallow Downy Woodpecker Blue-gray Gnatcatcher Common Grackle Eastern Phoebe Dickcissel Eastern Meadowlark European Starling Carolina Wren Brown Thrasher American Robin Eastern Kingbird Bell's Vireo
Agelaius phoeniceus Anas platyrhynchos Archilochus colubris Ardea herodias Cardinalis cardinalis Carduelis tristis Charadrius vociferous Cistothorus palustris Cistothorus platensis Colinus virginianus Cyanocitta cristata Dumetella carolinensis Empidonax traillii Geothlypis trichas Icterus galbula Icterus spurius Ixobrychus exilis Melospiza melodia Passerina caerulea Passerina cyanea Petrochelidon pyrrhonota Picoides pubescens Polioptila caerulea Quiscalus quiscula Sayornis phoebe Spiza americana Sturnella magna Sturnus vulgaris Thryothorus ludovicianus Toxostoma rufum Turdus migratorius Tyrannus tyrannus Vireo bellii
25
Effects of Prescribed Burning on Grassland Avifauna scale was estimated as 21.3 within those areas burned 2-4 years prior to sampling, 17.1 within those areas burned ≥5 years prior to sampling, and 15.4 within those areas burned 0-1 year prior to sampling. The species-area curves indicated that plots burned 2-4 years prior to sampling had a consistently higher level of species richness than the other burn category groups at all scales (Figure 2). Mean values of Shannon’s Diversity Index and Hill’s Diversity Index did not differ among burn category groups (Table 4). Table 3. Bird species observed outside of 50-m fixed-radius plots (n=81), including 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Common Name Species Wood Duck Great Egret Canada Goose Red-tailed Hawk Chimney Swift Northern Flicker American Crow Little Blue Heron Snowy Egret American Kestrel Barn Swallow Yellow-breasted Chat Red-bellied Woodpecker Northern Mockingbird Black-crowned Night Heron American White Pelican Double-crested Cormorant Black-capped Chickadee Purple Martin Northern Rough-winged Swallow Common Tern Warbling Vireo Mourning Dove
Aix sponsa Ardea alba Branta canadensis Buteo jamaicensis Chaetura pelagica Colaptes auratus Corvus brachyrhynchos Egretta caerulea Egretta thula Falco sparverius Hirundo rustica Icteria viren Melanerpes carolinus Mimus polyglottos Nycticorax nycticorax Pelecanus erythrorhynchos Phalacrocorax auritus Poecile atricapillus Progne subis Stelgidopteryx serripennis Sterna hirundo Vireo gilvus Zenaida macroura
26
Polymath: An Interdisciplinary Arts and Sciences Journal Table 4. Gamma species richness (S), Mean Species Richness ( S ), Shannon’s Diversity Index (H’) and Hill’s Diversity Index (N1) for 50-m fixed-radius plots (n=81), including 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Time Since Burn Diversity Indices Total (Gamma) Richness (S) Mean Species Richness ( S ) Shannon's Diversity Index (H’) Hill's Diversity Index (N1)
0-1 Year 21 6.74 1.55 4.03
2-4 years 26 7.54 1.68 4.50
≥5 Years 19 7.55 1.61 4.09
P -0.249 0.197 0.362
30
Species Richness
25 20 15
0-1 Years 2-4 Years ≥ 5 Years
10 5 0 0
5
10
15
20
25
30
Area (ha) Figure 2. Species-area curves showing the relationship between species richness and area (ha) within areas burned 0-1 year prior to sampling, 2-4 years prior to sampling, and ≥5 years prior to sampling. Estimated Density and Percent Occurrence The five most abundant bird species observed during the study, regardless of burn category group, included Red-winged Blackbird (Agelaius phoeniceus; 4.31/ha), Common Yellowthroat (Geothlypis trichas; 2.00/ha), Dickcissel (2.02/ha), Indigo Bunting (Passerina cyanea; 0.84/ha), and American Goldfinch (Carduelis tristis; 0.83/ha; Table 5). The most abundant species were also the most ubiquitous, with Red-winged Blackbird and Common Yellowthroat occurring within every study plot (Table 6). Dickcissels occurred within 93.8% of all study plots, while both Indigo Buntings and American Goldfinches occurred within 80.2% of study plots (Table 6). Other species commonly observed included Song Sparrow (Melospiza melodia; 48.1%), Northern Bobwhite (Colinus virginianus; 44.4%), and Sedge Wren (38.3%), while 25 species occurred on less than 25% of the survey plots (Table 6). 27
Effects of Prescribed Burning on Grassland Avifauna Table 5. Mean (± S.E.M.) number of individual birds per ha and results of one-way ANOVA (P) for 50m fixed radius plots (n=81), including 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling. Results of post hoc Scheffe’s Multiple-Comparison Test are indicated by different letters for significant comparisons. Common Name
Species
Red-winged Blackbird
Agelaius phoeniceus
4.26
± 0.26
4.29
Mallard
Anas platyrhynchos
0.01
± 0.01
--
Ruby-throated Hummingbird
Archilochus colubris
0.05
± 0.02a
0.18
Great Blue Heron
Ardea Herodias
0.01
± 0.01
--
Northern Cardinal
Cardinalis cardinalis
--
American Goldfinch
Carduelis tristis
0.67
Killdeer
Charadrius vociferous
Marsh Wren
0-1 Year
≥5 Years
2-4 Years
--
± 0.33 ±
--
± 0.05b --
4.43 -0.09
± 0.42 -± 0.05ab
P 0.933 0.524 0.037
--
--
0.524
--
0.219
0.06
± 0.05
--
± 0.14
0.97
± 0.12
0.92
0.01
± 0.01
--
Cistothorus palustris
0.08
± 0.05
0.08
± 0.04
0.02
± 0.02
0.639
Sedge Wren
Cistothorus platensis
0.29
± 0.05a
0.06
± 0.03 b
0.24
± 0.08ab
0.0041
Northern Bobwhite
Colinus virginianus
0.22
± 0.04
0.20
± 0.06
0.31
± 0.07
0.426
Blue Jay
Cyanocitta cristata
--
--
0.02
± 0.02
--
--
0.393
Gray Catbird
Dumetella carolinensis
--
--
0.05
± 0.05
--
--
0.393
Willow Flycatcher
Empidonax traillii
--
--
0.11
± 0.06a
0.14
± 0.06a
0.0395
Common Yellowthroat
Geothlypis trichas
2.22
1.74
± 0.12b
1.96
± 0.16ab
0.0259
Baltimore Oriole
Icterus galbula
--
--
0.03
± 0.03
--
--
0.393
Orchard Oriole
Icterus spurius
--
--
0.11
± 0.05
--
--
0.0106
Least Bittern
Ixobrychus exilis
--
--
--
± 0.12a
28
--
--
--
0.02
± 0.13 --
± 0.02
0.219 0.524
0.175
Polymath: An Interdisciplinary Arts and Sciences Journal Song Sparrow
Melospiza melodia
0.39
Blue Grosbeak
Passerina caerulea
--
Indigo Bunting
Passerina cyanea
0.79
Cliff Swallow
Petrochelidon pyrrhonota
Downy Woodpecker
0.20
± 0.05
0.28
± 0.09
0.184
0.05
± 0.03
0.02
± 0.02
0.152
± 0.11
1.05
± 0.13
0.61
± 0.11
0.0679
0.63
± 0.61
0.06
± 0.04
--
--
0.537
Picoides pubescens
0.01
± 0.01
--
--
--
--
0.524
Blue-gray Gnatcatcher
Polioptila caerulea
0.01
± 0.01
--
--
--
--
0.524
Common Grackle
Quiscalus quiscula
0.11
± 0.08
0.08
± 0.05
0.17
Eastern Phoebe
Sayornis phoebe
--
0.08
± 0.06
--
Dickcissel
Spiza americana
2.29
± 0.20
1.76
± 0.21
1.89
± 0.39
0.229
Eastern Meadowlark
Sturnella magna
0.04
± 0.02
0.15
± 0.08
0.09
± 0.04
0.234
European Starling
Sturnus vulgaris
--
--
--
0.09
± 0.09
0.175
Carolina Wren
Thryothorus ludovicianus
--
--
0.02
± 0.02
--
Brown Thrasher
Toxostoma rufum
0.04
± 0.03
0.03
± 0.02
0.02
± 0.02
0.944
American Robin
Turdus migratorius
0.04
± 0.03
0.17
± 0.11
0.02
± 0.02
0.257
Eastern Kingbird
Tyrannus tyrannus
0.06
± 0.05
0.02
± 0.02
0.07
± 0.04
0.612
Bell's Vireo
Vireo bellii
0.09
± 0.05
--
--
± 0.08 --
--
--
29
--
± 0.09 --
--
--
0.735 0.249
0.393
0.0275
Effects of Prescribed Burning on Grassland Avifauna Table 6. Percent occurrence of bird species detected within 50-m fixed-radius plots (n=81), including 35 plots burned 0-1 year prior to sampling, 28 plots burned 2-4 years prior to sampling, and 18 plots burned ≥5 years prior to sampling.
Common Name
Species
Red-winged Blackbird Mallard Ruby-throated Hummingbird Great Blue Heron Northern Cardinal American Goldfinch Killdeer Marsh Wren Sedge Wren Northern Bobwhite Bluejay Gray Catbird Willow Flycatcher Common Yellowthroat Baltimore Oriole Orchard Oriole Least Bittern Song Sparrow Blue Grosbeak Indigo Bunting Cliff Swallow Downy Woodpecker Blue-gray Gnatcatcher Common Grackle Eastern Phoebe Dickcissel Eastern Meadowlark European Starling Carolina Wren Brown Thrasher American Robin Eastern Kingbird Bell's Vireo
Agelaius phoeniceus Anas platyrhynchos
100.0 2.9
100.0 3.6
100.0 0.0
100.0 2.5
Archilochus colubris Ardea herodias Cardinalis cardinalis Carduelis tristis Charadrius vociferous Cistothorus palustris Cistothorus platensis Colinus virginianus Cyanocitta cristata Dumetella carolinensis Empidonax traillii Geothlypis trichas Icterus galbula Icterus spurius Ixobrychus exilis Melospiza melodia Passerina caerulea Passerina cyanea Petrochelidon pyrrhonota Picoides pubescens Polioptila caerulea Quiscalus quiscula Sayornis phoebe Spiza americana Sturnella magna Sturnus vulgaris Thryothorus ludovicianus Toxostoma rufum Turdus migratorius Tyrannus tyrannus Vireo bellii
11.4 2.9 0.0 60.0 2.9 11.4 54.3 45.7 0.0 0.0 0.0 100.0 0.0 0.0 0.0 57.1 0.0 80.0 5.7 2.9 2.9 8.6 0.0 100.0 8.6 0.0 0.0 5.7 5.7 5.7 0.0
39.3 0.0 7.1 100.0 0.0 10.7 14.3 32.1 3.6 3.6 14.3 100.0 3.6 17.9 0.0 39.3 10.7 85.7 7.1 0.0 0.0 10.7 7.1 85.7 17.9 0.0 3.6 7.1 10.7 3.6 14.3
16.7 0.0 0.0 88.9 0.0 5.6 44.4 61.1 0.0 0.0 27.8 100.0 0.0 0.0 5.6 44.4 5.6 72.2 0.0 0.0 0.0 22.2 0.0 94.4 22.2 5.6 0.0 5.6 5.6 16.7 0.0
22.2 1.2 2.5 80.2 1.2 9.9 38.3 44.4 1.2 1.2 11.1 100.0 1.2 6.2 1.2 48.1 4.9 80.2 4.9 1.2 1.2 12.3 2.5 93.8 14.8 1.2 1.2 6.2 7.4 7.4 4.9
30
2-4 Years
≥5 Years
0-1 Year
All Plots
Polymath: An Interdisciplinary Arts and Sciences Journal Indicator Species Analysis Ten species were found to have significant (P
