Nesting Success and Population Densities of Grassland Birds in the Breeding and Wintering Seasons in Tennessee and Kentucky PDF Download
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Author: Publisher: ISBN: Category : Bird populations Languages : en Pages : 165
Book Description
Grassland and shrub/scrub breeding birds have experienced severe population declines since the beginning of the Breeding Bird Survey in 1966 (Sauer et al. 2007). Habitat loss and degradation are likely the primary causes of decline (Herkert 1994, Warner 1994, Johnson and Igl 2001). Partners in Flight (PIF) continental population objectives call for managers to increase populations by up to 100% for several of the species found in the Big Barrens, north-central Tennessee and south-central Kentucky, such as Dickcissel (Spiza americana), Henslow's Sparrow (Ammodramus henslowii), and Prairie Warbler (Dendroica discolor; Rich et al. 2004). The quantity and quality of breeding season habitat are important in determining the future population trends of grassland birds throughout North America. Herkert (1995) identified the loss and degradation of breeding season habitat as the most likely cause of most population declines. It is important to determine the relative importance of habitat features for grassland birds on multiple scales in terms of population density as well as productivity. I compared population densities of breeding grassland birds in the Big Barrens with field characteristics (e.g. field size, vegetation measurements) to determine which habitat features promoted field use by each species (Chapter 2). I also monitored 39 Henslow's Sparrow nests and 122 Field Sparrow nests in the Big Barrens during the 2006 and 2007 breeding seasons (Chapter 3). Estimates of Mayfield (1961, 1975) nest success were within the documented ranges for both Henslow's Sparrow (23.8%, 95% CI: 10.7 - 40.5%) and Field Sparrow (15.4%; 95% CI: 9.5 - 23.1%). I also found evidence that Field Sparrows are at least double-brooded in the Big Barrens. In addition to my work in the Big Barrens during the breeding season, we also sampled the winter bird community in the Big Barrens and in eastern Tennessee from 2003-07 using a variety of methods, including mist netting, widely dispersed point counts, rope dragging transects, and line transects (Chapter 4). My results indicated that a variety of habitats, including disturbed fields and agricultural fields in addition to grasslands dominated by native vegetation, is necessary to support the entire winter grassland bird community in the mid-South.
Author: Publisher: ISBN: Category : Bird populations Languages : en Pages : 165
Book Description
Grassland and shrub/scrub breeding birds have experienced severe population declines since the beginning of the Breeding Bird Survey in 1966 (Sauer et al. 2007). Habitat loss and degradation are likely the primary causes of decline (Herkert 1994, Warner 1994, Johnson and Igl 2001). Partners in Flight (PIF) continental population objectives call for managers to increase populations by up to 100% for several of the species found in the Big Barrens, north-central Tennessee and south-central Kentucky, such as Dickcissel (Spiza americana), Henslow's Sparrow (Ammodramus henslowii), and Prairie Warbler (Dendroica discolor; Rich et al. 2004). The quantity and quality of breeding season habitat are important in determining the future population trends of grassland birds throughout North America. Herkert (1995) identified the loss and degradation of breeding season habitat as the most likely cause of most population declines. It is important to determine the relative importance of habitat features for grassland birds on multiple scales in terms of population density as well as productivity. I compared population densities of breeding grassland birds in the Big Barrens with field characteristics (e.g. field size, vegetation measurements) to determine which habitat features promoted field use by each species (Chapter 2). I also monitored 39 Henslow's Sparrow nests and 122 Field Sparrow nests in the Big Barrens during the 2006 and 2007 breeding seasons (Chapter 3). Estimates of Mayfield (1961, 1975) nest success were within the documented ranges for both Henslow's Sparrow (23.8%, 95% CI: 10.7 - 40.5%) and Field Sparrow (15.4%; 95% CI: 9.5 - 23.1%). I also found evidence that Field Sparrows are at least double-brooded in the Big Barrens. In addition to my work in the Big Barrens during the breeding season, we also sampled the winter bird community in the Big Barrens and in eastern Tennessee from 2003-07 using a variety of methods, including mist netting, widely dispersed point counts, rope dragging transects, and line transects (Chapter 4). My results indicated that a variety of habitats, including disturbed fields and agricultural fields in addition to grasslands dominated by native vegetation, is necessary to support the entire winter grassland bird community in the mid-South.
Author: Alyssa Lauren DeRubeis Publisher: ISBN: Category : Dickcissel Languages : en Pages : 188
Book Description
Dwindling populations of North American grassland birds are linked to habitat loss. Tallgrass prairie only covers 3% of its pre-settlement-era range. Small-scale restoration projects attempt to increase acreage for prairie avifauna, and while some breeding grassland species are present at these sites, nesting success and non-breeding use are still largely unknown. Both life history aspects are required for effective grassland bird conservation. My first objective was to access nest success of the Dickcissel (Spiza americana) at two remnant and two restored tallgrass prairies in Northwest Arkansas. From May-August 2017 and 2018, I found 114 nests that I monitored to determine ultimate fate. I selected vegetative characteristics collected at nest and random sites combined with site-level variables to inform a logistic exposure model. Mean nest success was 8.5%, which varied by site but appeared unaffected by restoration status. Excluding predator presence, the most important predictors of nest success were site size size and brood parasitism. Prairie Kingsnake (Lampropeltis calligaster) was the primary nest predator. My second objective was to identify field site characteristics and vegetation use by non-breeding grassland-obligate birds in two remnant and three restored tallgrass prairies in Northwest Arkansas. Between September 2017 and May 2018, I tallied 44 species. Only eight species were grassland-obligate, but this assemblage accounted for about half of all detections. Grassland-obligate diversity was similar across seasons and between sites, except for a small isolated restored prairie which hosted much lower diversity. Dickcissel and Sedge Wren (Cistothorus platensis) detection rates increased significantly with distance to woody edge, indicating area sensitivity. Some species used primarily grass and forb, others utilized burned areas, and Le Conte's Sparrow (Ammodramus lecontei) frequented shrubs. Northwest Arkansas' remnant and restored tallgrass prairies are valuable for nesting Dickcissel and a suite of non-breeding grassland birds. Special consideration for maintaining large parcels with fire that are distant from paved roads should be given for breeding Dickcissel. Acquiring large parcels and maintaining a shifting vegetation mosaic while retaining some woody vegetation could satisfy diverse habitat preferences for non-breeding grassland avifauna.
Author: David Joseph Horn Publisher: ISBN: Category : Birds Languages : en Pages : 222
Book Description
Results of habitat fragmentation studies on grassland and wetland birds are not consistent. Some studies have found positive relationships among abundance, nest success, field size, and distance to edges, whereas others have found no relationship. One reason for differing results may be the landscape composition in which the study took place. I examined how landscape composition influenced relations among: 1) occurrence and abundance of grassland songbirds and field size and 2) nest success of ducks, field size, and edges. I also investigated the effects of mowing on grassland songbirds, and how landscape features, such as amount of perennial grassland, and predator community composition influenced the nest success of ducks in fields. The study took place in the Prairie Pothole Region of central North Dakota during the 1996-1997 breeding seasons. Two types of 6.4 x 6.4 km study areas were selected based on the amount of perennial grassland they contained: 15-20% and 51-55%. The remaining portion of the study areas was primarily cropland and wetland.
Author: Charles P. Nicholson Publisher: ISBN: 9780870499876 Category : Nature Languages : en Pages : 426
Book Description
Atlas of the Breeding Birds of Tennessee is based on research conducted from 1986 through 1991 by the Tennessee Ornithological Society and is the first study of its kind ever published for the state. It reviews the methodology employed in the study, which included innovative miniroute censuses. It features detailed accounts of individual species which include both grid maps that plot their distribution and contour maps that reflect their relative abundance. The accompanying text for each species discusses its geographical and historical occurrence, cites habitat preferences, and offers notes on breeding biology such as nest placement and clutch size. Line drawings accurately portray the birds in their nesting cycle. In addition to this wealth of data on individual species, the atlas provides background information on the physical and cultural geography of Tennessee and on patterns of land-use change that followed the arrival of European settlers. It also presents the most comprehensive history of ornithology in the state yet published.
Author: Dylan J. Smith Publisher: ISBN: Category : Languages : en Pages : 0
Book Description
Many North American bird populations are declining, and of those, grassland bird populations are declining most rapidly, having been reduced by about half since 1970. Such declines are difficult to study, both because grasslands are characterized and maintained by disturbance, and because grassland birds have a high propensity for dispersal. The primary cause for population declines is habitat loss. For example, only ~14% of pre-European colonization eastern tallgrass prairie remains intact. Even where habitat remains, many species continue to decline, and these declines may be due to reductions in reproductive success. One potential cause of these local declines is the encroachment of woody vegetation on grasslands, which for grassland birds reduces the overall amount and degrades the quality of usable habitat. In addition, local demographic changes cause-and are caused by-regional- or continental-scale patterns. Thus, broad spatial approaches are needed to best understand the drivers of demographic change. In my first chapter, I sought to identify whether woody encroachment, via reductions in reproductive success, can explain changes in population abundance. I compiled and analyzed data on nest contents and nest success collected at Konza Prairie Biological station over nearly five decades. Nest success did not change since 1971, but the frequency of Brown-headed Cowbird (Molothrus ater) brood parasitism increased. In addition, grassland obligates were harder hit than species that prefer woodier habitat, supporting the idea that grassland degradation most strongly affects birds that rely on pristine prairie. In chapter 2, I tested alternative mechanisms linking the high degree of climatic variability in the Great Plains to inter-annual fluctuations breeding distribution and local abundance of a common grassland bird species, Grasshopper Sparrows (Ammodramus savannarum perpallidus). I used 11 years of citizen science data from eBird spanning the entire Great Plains to determine whether overwinter mortality, temperature during migration, or precipitation during the preceding year's growing season and vegetation phenology best predicted local abundance. The start date of the growing season and the total precipitation in the preceding year's growing season correlated most strongly with sparrows' interannual settlement decisions. Local abundance was highest in areas where the growing season started before March and where the preceding year's growing season precipitation was low. The drivers of population declines and movement decisions in grassland birds are complex and often indirect or delayed. As grasslands face ongoing anthropogenic threats ranging from agricultural development to fire suppression and climate change, identifying the distributional and demographic responses of grassland birds will be crucial to conserving this declining group of species.
Author: Kyle A. Brazil Publisher: ISBN: Category : Grasses Languages : en Pages : 0
Book Description
Eastern grassland bird populations have been declining since the Breeding Bird Survey was initiated in 1966. The cause of the decline is the near-complete loss of their native grassland habitats. A driver of the loss of native grasslands in the East is the conversion of native grasses to the introduced species tall fescue (Lolium arundinaceum). Tall fescue, a cool-season grass, provides livestock forage during fall and spring, but does not provide habitat for most grassland bird species due to its dense, sod-forming structure. Wildlife biologists have recommended the incorporation of native warm-season grass (NWSG) pastures into grazing systems as a solution to the grassland bird decline that will also benefit beef cattle producers. However, little data exists on the efficacy of this practice for grassland bird conservation or beef cattle production when pastures are managed the way a typical producer is likely to manage them, with continuous, season-long (May – August) grazing. I designed an experiment to compare grassland bird density and nest survival in NWSG cattle pastures among two continuous, season-long stocking strategies: continuous (CONT) and heavy-early (HEAVY), and traditionally-managed tall fescue pastures (FESCUE) during summers 2015 – 2017. Animal performance of weaned steers, pasture production, and sward sustainability were recorded throughout the study. I developed an enterprise-level economic model to determine the impact of incorporating the perennial warm-season grasses switchgrass (Panicum virgatum) and bermudagrass (Cynodon dactylon) on profitability of beef cattle operations in the Fescue Belt. Grasshopper sparrow (Ammodramus savannarum) density was three times greater in NWSG (0.30 males/ha) than FESCUE pastures (0.11 males/ha), and both species selected to nest in NWSG and selected against nesting in FESCUE pastures. Average daily gain of steers was similar between CONT (0.98 kg/d) and HEAVY (0.89 kg/d) and was comparable to other NWSG grazing studies, and both stocking strategies were sustainable over the study period. Incorporating switchgrass into simulated tall fescue forage systems increased profitability over 100% fescue systems by 1,070% and 42% for spring- and fall-calving herds, respectively. The results of my study indicate that continuously-grazed NWSG pastures in the Fescue likely contribute to both grassland bird conservation and beef cattle production.
Author: Christopher M. Lituma Publisher: ISBN: Category : Languages : en Pages :
Book Description
The prairies of North America have undergone substantial changes since European settlement in the 1800's, with some estimates suggesting that 96% of the tallgrass prairie has been converted. Multiple factors contributed to reduction in prairie, including: grazing, row-crop farming, depressed fire regimes, and exotic grass species introduction. In Texas, 35% of the historic grassland ecosystems have been either altered or converted. Introduced in the 1940's, exotic grass species such as Bermuda grass (Cynodon sp) have displaced native grass species throughout Texas. Introduced grass species can alter the existing plant communities degrading habitat for birds and other animals. Grassland birds are declining faster than any other bird group within North America; due in part to a reduction in suitable breeding habitat. I addressed this issue by comparing nesting success of grassland birds between exotic grass sites and restored native grass sites in the blackland prairie region of east-central Texas during 2007-2008 breeding seasons. I conducted point counts and nest searching from March - July. Point count data indicate no difference in species richness between sites. Dickcissel (Spiza americana) nests represented 89% of the nests found (n = 104). Dickcissel abundance was 44% higher in restored sites and 76% of nests were located in restored sites. Daily survival (DSR) for dickcissels in restored sites was 0.895 (SE = 0.013) and for exotic sites was 0.930 (SE = 0.017). I used an independent samples t-test to compare mean nest height, which was 56% higher in restored sites than exotic sites (n = 83, x bar = 38.0 cm "1.90; x bar = 15.2 cm plus/minus 2.19, df = 81, t = -6.31, P = 0.001), and mean nest substrate height which was 58% higher in restored sites than in exotic sites (n = 83, x bar = 118.8 cm " 6.50; x bar = 46.5 cm " 4.77, df = 81, t = -6.08, P = 0.001). Although dickcissel abundance was greater in restored sites than exotic sites, their observed nesting success and DSR was lower in restored sites. This is indicative of an ecological trap, which occurs when an organism is attracted to a habitat that negatively impacts the organism. Some research suggests that restored fields in other states are acting as traps for dickcissels, and according to my results restored sites I sampled may also be acting as ecological traps for dickcissels in Texas.
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Author: Alyssa Lauren DeRubeis
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Author: David Joseph Horn
Author: Charles P. Nicholson
Author: Thomas F. Fondell
Author: Dylan J. Smith
Author: David Anthony Swanson
Author: Kyle A. Brazil
Author: Christopher M. Lituma