Avian Community Response to Grazing Intensity on Monoculture and Mixed Florida Pastures

Monoculture and mixed pastures in Florida provide habitat for a variety of resident and migratory bird species. The objectives of this study were to investigate the effects of grazing on vegetation structure and bird species richness and abundance in grazed monoculture and mixed pastures. Study pasture units were subject to four cattle grazing intensities: 0 = nongrazed (control), 15 = low, 20 = medium, or 35 = high animal units (AU) per pasture unit (no cattle, 1.3, 1.0, and 0.6 ha · AU^?1, on monoculture pastures and no cattle, 2.1, 1.6, and 0.9 ha · AU^?1, on mixed pastures). Monoculture pastures displayed a greater decrease in spatial heterogeneity of the vegetative community in the presence of grazing than mixed pastures. An increase in grazing intensity led to declines in total avian species richness and abundance and species richness within short-distance migrant, neotropical migrant, and permanent resident guilds on monoculture pastures. Declines in total species richness and abundance and neotropical migrant guild species richness and abundance were observed on mixed pastures subject to increasing grazing intensity. However, species richness within short-distance migrant and urban guilds and abundance within the grassland guild increased on this pasture type in the presence of grazing. Loss of spatial heterogeneity typically results in a lack of suitable habitat for birds that occupy the extremes of the vegetation structure gradient. This can lead to a loss of species richness and abundance. For the majority of avian guilds, a low grazing intensity of 1.3 ha · AU^?1 and 2.1 ha · AU^?1 on monoculture and mixed pasture, respectively, is recommended to maintain abundance. However, these grazing intensities may result in declines in species richness. Ultimately, if a range of avian species are to be supported on monoculture and mixed pastures, spatial heterogeneity of plant structure and composition must be maintained.     

Adaptive,Multipaddock Rotational Grazing Management: A Ranch-Scale Assessment of Effects on Vegetation and Livestock Performance in Semiarid Rangeland

A comprehensive understanding of multipaddock, rotational grazing management on rangelands has been slow to develop, and the contribution of adaptive management (Briske et al. 2011) and sufficient scale (Teague and Barnes 2017) have been identified as key omissions. We designed an experiment to compare responses of vegetation and cattle in an adaptively managed, multipaddock, rotational system with that of a season-long, continuous system at scales comparable with those of a working ranch. We hypothesized that 1) year-long rest periods in the adaptively managed, rotational pastures would increase the density and productivity of perennial C₃ graminoids compared with continuously grazed pastures and 2) adaptive management, supported with detailed monitoring data, would result in similar cattle performance in the rotational as in the continuously grazed pastures. However, we found little supporting evidence for grazing management effects on C₃ graminoid abundance or production under either above-average or below-average precipitation conditions during the 5-yr experiment. Furthermore, adaptive rotational grazing resulted in a 12–16% reduction in total cattle weight gain relative to continuous grazing each year. Our work shows that the implementation of adaptive management by a stakeholder group provided with detailed vegetation and animal monitoring data was unable to fully mitigate the adverse consequences of high stock density on animal weight gain. Under adaptive rotational grazing, C₃ perennial grass productivity and stocking rate both increased following above-average precipitation. But when adaptive rotational management was directly compared with continuous grazing with the same increase in stocking rate, continuous grazing achieved similar vegetation outcomes with greater cattle weight gains. We suggest that managers in semiarid rangelands strive to maintain cattle at stock densities low enough to allow for maximal cattle growth rates, while still providing spatiotemporal variability in grazing distribution to enhance rangeland heterogeneity and long-term sustainability of forage production.     

Grazing Intensity Influences Ground Squirrel and American Badger Habitat Use in Mixed-Grass Prairies

Ground squirrel (Spermophilus spp.) and American badger (Taxidea taxus) burrowing activities are ecologically important disturbances that contribute to the heterogeneity of prairie environments. These activities also have a strong impact on habitat suitability for many other grassland species. However, effects of cattle grazing intensity on ground squirrel and American badger burrows are not well understood. From 2006 to 2012 we evaluated effects of grazing intensity and vegetation type on American badger burrow occurrence and ground squirrel burrow abundance using a manipulative grazing experiment in Grasslands National Park of Canada, Saskatchewan. The study area consisted of nine 300-ha pastures at a range of stocking rates, from very low to very high for the region. Each pasture had 10 plots (six upland and four lowland) where vegetation and burrow surveys were completed. Burrow abundance and occurrence as well as vegetation structure were assessed for 2 yr prior to the introduction of cattle to this landscape in 2008, which followed at least 15 yr without livestock, and from 2009 to 2012, following introduction of livestock. Data were analyzed using generalized linear mixed models. In upland habitats, ground squirrel burrow counts increased with increasing grazing intensity and decreasing vegetation biomass; conversely, badger burrow occurrence increased with decreased stocking rates and increasing average litter cover and vegetation biomass. Abundance and occurrence of both ground squirrel and badger burrows in lowland habitats was relatively independent of grazing intensity or vegetation. Vegetation composition had little impact on ground squirrel or badger burrows. A range of grazing intensities may contribute to maintaining diversity of burrowing mammals in prairie environments.     

Effects of human disturbance on nest placement of the woodpigeon (Columba palumbus): a case study from the Middle Atlas,Morocco

The woodpigeon (Columba palumbus) is a common and widespread bird in Morocco (North Africa). I examined, over 2 years (2010 and 2011), the breeding density and nest placement of this game species in relation to nest site habitat and degree of human disturbance. The study area was in the Middle Atlas Tighboula mountain forest, Morocco, in a disturbed and an undisturbed site. Using data collected in the 2 study sites, I aimed to identify the factors influencing the placement of nests within holm oak trees (Quercus rotundifolia) and their densities. I found that habitat structures, influenced by grazing disturbance, have affected nesting density and the location of nests of this species. Woodpigeons place their nests in a higher position (3.42 ± 0.19 m) when disturbance intensity is high and lower (1.68 ± 0.1 m) when disturbance intensity is low, and show higher nesting density in less disturbed zone (3.1 ± 0.4 nests/ha) than in highly disturbed zones (1.4 ± 0.2 nests/ha). Grazing disturbance could pose a threat to population persistence at a broader scale and could potentially reduce the abundance of this species by altering the composition and the structure of the forest nesting habitat. Further multi‐scale studies are needed to assess the effects of different levels of grazing disturbance on woodpigeon nest density and placement, and to enhance our knowledge of the breeding behavior of this game species under variable environments.     

Effects of Livestock Grazing Management on Grassland Birds in a Northern Mixed-Grass Prairie Ecosystem

Grassland birds have undergone substantial population declines throughout much of their historic ranges in North America. Most of the remaining grassland bird habitat is restricted to rangelands managed for livestock production, so grazing management has strong implications for grassland bird conservation efforts. We conducted 1 830 point-count surveys at 305 sites during 2016–2017 to evaluate the relative effects of three livestock grazing systems on the abundance and community composition of grassland birds in a northern mixed-grass prairie ecosystem of eastern Montana, United States. Our objectives were to 1) evaluate effects of grazing management on abundance and community composition of grassland obligate birds, focusing specifically on grazing systems, stocking rates, and interactions with rangeland productivity; 2) evaluate the importance of local vegetation characteristics for grassland birds within grazing systems; and 3) assess the effectiveness of rest-rotation grazing to create patch-heterogeneity in rangeland vegetation through the alteration of structural components and the response of grassland birds to these treatments. Overall, we found inconsistent responses in abundances of grassland birds relative to livestock grazing systems and no discernable differences among grazing systems relative to community composition. However, local abundances were often driven by interactions between grazing system and rangeland production potential, suggesting the effects of livestock grazing management were generally mediated by rangeland productivity. In addition, associations between avian abundance and grazing management parameters (e.g., stocking rate) were species specific. Ubiquitous guidelines for livestock grazing systems may be inappropriate for grassland bird conservation efforts in the northern mixed-grass prairie, and high stocking rates may negatively impact populations of dense-grass obligate grassland birds in this region.     

Grazing Systems Do Not Affect Bird Habitat on a Sandhills Landscape

Grassland birds are declining faster than any other guild of birds in North America, in part because of degradation of their breeding habitat. Rangeland managers recommend increasing heterogeneity to improve biodiversity; however, on privately owned rangelands, beef production likely decreases heterogeneity on the landscape. One suggestion has been to use multiple grazing systems across a landscape to increase heterogeneity and provide benefits for avian biodiversity, but there is little research to support this recommendation. Thus, our goal was to examine heterogeneity and songbird abundance in relation to grazing systems used by private producers in a large, intact rangeland region. We measured vegetation structure and conducted avian surveys in the Nebraska Sandhills on 11 management units with five different grazing systems, including season-long continuous, deferred rotation, management intensive, dormant season only, and a fixed rotation. On each management unit we assessed the relationship between vegetation structure or songbird abundance and potential management effects, such as grazing system, stocking rate, and management intensity. Season of use and stocking rate were the most common sources of variation in vegetation structure and songbird abundance. Grazing system did not explain variation in vegetation structure or bird abundance, except for heterogeneity in live grass cover, litter cover, shrub cover, and abundance of field sparrows. Vegetation structure varied across the landscape we sampled, but the range of heterogeneity was narrow. Thus, managers should not assume that using a variety of grazing systems across a landscape will inevitably result in heterogeneity of vegetation structure. Rather, managers should focus on creating contrasting vegetation structure in large areas to increase large-scale heterogeneity. This may be achieved through the application of more extreme management practices (e.g., long-term heavy grazing and long-term rest or patch-burn grazing) so that a wider variety of vegetation composition and structure is available to support biodiversity.     

Pyric–Herbivory and Cattle Performance in Grassland Ecosystems

Achieving economically optimum livestock production on rangelands can conflict with conservation strategies that require lower stocking rate to maintain wildlife habitat. Combining the spatial and temporal interaction of fire and grazing (pyric–herbivory) is a conservation-based approach to management that increases rangeland biodiversity by creating heterogeneous vegetation structure and composition. However, livestock production under pyric–herbivory has not been reported. In both mixed-grass prairie and tallgrass prairie, we compared livestock production in pastures with traditional fire and grazing management (continuous grazing, with periodic fire on tallgrass prairie and without fire on mixed-grass prairie) and conservation-based management (pyric–herbivory applied through patch burning) at a moderate stocking rate. Stocker cattle weight gain, calf weight gain, and cow body condition score did not differ (P > 0.05) between traditional and conservation-based management at the tallgrass prairie site for the duration of the 8-yr study. At the mixed-grass prairie site, stocker cattle gain did not differ in the first 4 yr, but stocker cattle gained more (P ≤ 0.05) on conservation-based management and remained 27% greater for the duration of the 11-yr study. Moreover, variation among years in cattle performance was less on pastures under conservation management. Traditional management in mixed-grass prairie did not include fire, the process that likely was associated with increased stocker cattle performance under conservation management. We conclude that pyric–herbivory is a conservation-based rangeland management strategy that returns fire to the landscape without reduced stocking rate, deferment, or rest.     

Integrated Ecological and Economic Analysis of Ranch Management Systems: An Example From South Central Florida

Developing sustainable ranch management systems requires integrated research that examines interrelations among ecological and economic factors. In south central Florida, where phosphorus (P) loading is an overriding environmental concern, we established an interdisciplinary experiment to address the effects of cattle stocking density and pasture type on P loading and other ecological and economic factors in subtropical Florida ranchlands through a partnership including ecologists, agricultural faculty, agency personnel, and producers. Here we present an overview of all project components detailed in 3 accompanying papers in this issue of Rangeland Ecology & Management. We describe the experimental design, which included 2 replicates of 4 different cattle stocking density treatments (control, low, middle, and high [0, 15, 20, and 35 cow–calf pairs per pasture]) maintained on 8 improved summer pastures (∼ 20 ha each), and 8 seminative winter pastures (∼ 32 ha each) from 1998 to 2003. Stocking densities did not significantly affect P loads and concentrations in surface runoff, soil chemistry, or soil nematode communities, but did affect cattle production and economic performance. Cattle production was greater at the high than at the middle or low stocking density; economic performance declined significantly with decreasing stocking density (break-even was $1.89·kg^-1 for high and $2.66·kg^-1 for low density). Pasture type significantly affected environmental factors; average P runoff from improved summer pastures (1.71 kg P·ha^-1·y^-1) was much greater than from seminative winter pastures (0.25 kg P·ha^-1·y^-1), most likely because of past P fertilizer use in improved pastures. We integrate results from all the papers within the context of a conceptual model and a P budget, and emphasize that management practices targeted at specific environmental factors on beef cattle ranches, such as nutrient loading, must include consideration of economic impacts and broader ecosystem implications.     

Soil Phosphorus,Cattle Stocking Rates,and Water Quality in Subtropical Pastures in Florida,USA

Minimizing nonpoint source nutrient pollution is important to the sustainability of grazing lands. Increased nutrient loads have reduced water quality in Lake Okeechobee in south Florida, prompting establishment of a Total Maximum Daily Load (TMDL) that will require large reductions in phosphorus (P) runoff into the lake. A significant portion of this reduction must come from beef cattle ranches, the major land use in the region. A large-scale research project, consisting of a 420-ha array of 8 improved summer and 8 semi-improved winter pastures, was established from 1998–2003 to investigate the influence of beef cattle stocking rate on nutrient loads in surface runoff. Each pasture type had two replicates of four different cattle stocking rates including a control with no cattle and stocked pastures with low, medium, and high stocking rates (1.3, 1.0, 0.6 ha·AU^-1 [animal unit] in summer pastures; 2.1, 1.6, and 0.9 ha·AU^-1 in winter pastures). Cattle stocking rate did not affect nutrient concentrations or loads in surface runoff during the study period. Average annual P discharges were 1.71 kg·ha^-1 from summer pastures and 0.25 kg·ha^-1 from winter pastures. Average total P concentrations in runoff were 0.63 mg·L^-1 for summer pastures and 0.15 mg·L^-1 for winter pastures. Differences in runoff P were related to differences in soil P test results, a difference believed to be due to prior fertilization practices. Our findings show that reducing cattle stocking rates on beef cattle pastures is not an effective practice for reducing nutrient loads, and that accumulation of P in soil from historical fertilization has an overriding influence on P loads in surface runoff. Results indicate that reducing the overall volume of surface discharges would be a more effective strategy than altering cattle stocking practices to reduce nonpoint runoff of P from cattle pastures in this region.     

Stocking Rate and Fuels Reduction Effects on Beef Cattle Diet Composition and Quality

An experiment was conducted to evaluate the influence of forest fuels reduction on diet quality, botanical composition, relative preference, and foraging efficiency of beef cattle grazing at different stocking rates. A split plot factorial design was used, with whole plots (3 ha) being fuel reduced or no treatment (control), and split plots (1 ha) within whole plots were grazed to three levels of forage utilization; (low) 3 heifers · ha^?1, (moderate) 6 heifers · ha^?1, (high) 9 heifers · ha^?1, with a 48-h grazing duration. Grazing treatments were applied in August of 2005 and 2006. Cattle diet composition and masticate samples were collected during 20-min grazing bouts using six ruminally cannulated cows in each experimental unit. Relative preference indices indicated a strong preference for grass regardless of treatment and stocking rate. Grass consumption was lower in control pastures (P < 0.05) and tended (P < 0.095) to decrease with increased stocking rates. Shrub use was higher in control pastures displaying a quadratic effect (P < 0.05) due to stocking, whereas shrub use increased with stocking rate across all treatments. Cattle grazing control pastures consumed diets higher in crude protein compared to cattle grazing treated pastures (P < 0.05). In vitro dry matter digestibility values were lower (P < 0.05) in control sites and tended (P = 0.10) to decrease with increased stocking rates. In both control and treated pastures, bites per minute and grams consumed per minute declined (P = 0.003) with increased stocking, indicating foraging efficiency of cattle decreases with increased stocking rates. Our data indicated cattle grazing late season grand fir habitat types have a strong preference for grasses regardless of treatment or stocking rate. However, as stocking rate increased in both control and treated pastures, grass consumption decreased, shrub consumption increased, and foraging efficiency decreased.     

Stocking Rate Effects on Steer Performance for Two Methods of Alleviating Fescue Toxicosis

Generally, grazing endophyte-infested tall fescue (Festuca arundinace Schreb.) in the late spring and summer is not recommended because of the effects of fescue toxicosis on cattle weight gains, which can be extreme. For steers conditioned to graze tall fescue in the early spring, stocking rate (3, 4, 5, and 6 steers/ha) effects were evaluated for two methods designed to avoid poor cattle performance during the late spring and summer (compensation period). The evaluation was conducted in 1997 and 1998. During the compensation phase, one replicate of each stocking rate was randomly assigned to 1-ha pastures of eastern gamagrass (Tripsacum dactyloides L.), and the other replicate of each stocking rate remained on tall fescue; the steers were fed a 1:1 mixture of broiler litter and corn at 2.27 kg as fed/steer per d. Average daily gain for steers fed eastern gamagrass during the compensation phase declined linearly (P<0.05) as stocking rate increased, but ADG for steers fed tall fescue plus the broiler litter-corn mixture tended to increase (P<0.10) as stocking rate increased. As a result, ADG and live weight gain (kilograms per hectare) with heavier stocking rates were higher for steers fed tall fescue plus the broiler litter-corn mixture, whereas the responses at a lighter stocking rate were higher for steers fed eastern gamagrass. At the conclusion of the compensation phase in 1998, steers fed tall fescue plus the broiler litter-corn mixture had lower (P<0.05) serum prolactin levels, and a higher (P<0.05) proportion of steers fed tall fescue had rough hair coats compared with those fed eastern gamagrass. Results of this study show that, for steers grazing tall fescue pastures, either eastern gamagrass or supplementation with a broiler litter-corn mixture can provide acceptable performance, but responses are affected by grazing pressure. Symptoms of fescue toxicosis can still occur, however.     

Grazing Management and Microclimate Effects on Cattle Distribution Relative to a Cool Season Pasture Stream

Because of concerns about the impact of grazing management on surface water quality, a 3-yr study was conducted to determine grazing management and microclimate impacts on cattle distribution relative to a pasture stream and shade. Three treatments, continuous stocking with unrestricted stream access (CSU), continuous stocking with restricted stream access (CSR), and rotational stocking (RS), were evaluated on six 12.1-ha cool-season grass pastures stocked with 15 fall-calving Angus cows (Bos taurus L.) from mid-May through mid-October of each year. On 2 d · mo^?1 from May through September of each year, a trained observer in each pasture recorded cattle position and activity every 10 min from 0600 to 1800 hours. In years 2 and 3, position of one cow per pasture was recorded with a Global Positioning System (GPS) collar at 10-min intervals 24 h · d^?1 for 2 wk · mo^?1 from May through September. In week 2 of collar deployment in May, July, and September, cattle had access to off-stream water. Ambient temperature, black globe temperature, relative humidity, and wind speed were recorded at 10-min intervals and temperature humidity (THI), black globe temperature humidity (BGTHI), and heat load (HLI) indices were calculated. Based on GPS collars, mean percentage of time cows in CSU pastures were in the stream (1.1%) and streamside zone (10.5%) were greater (P < 0.05) than cows in CSR (0.2% and 1.8%) or RS (0.1% and 1.5%) pastures. Based on GPS collar data, off-stream water did not affect the percentage of time cattle in CSU or CSR pastures spent in the stream. Probabilities that cattle in CSU and CSR pastures were in the stream or riparian zones increased (P < 0.05) as ambient temperature, black globe temperature, THI, BGTHI, and HLI increased. Rotational stocking and restricted stream access were effective strategies to decrease the amount of time cattle spent in or near a pasture stream.     

Tick Abundance and Levels of Infestation on Cattle in Response to Patch Burning

Patch burning (PB) uses frequent, spatially discrete fires throughout a pasture to create variation in the composition and structure of the plant community. The complex vegetation changes incurred from this type of burning regimen in addition to the focal grazing of cattle induced by PB should reduce tick populations by creating less favorable microhabitats. To determine if a reduction in tick populations occurred on PB pastures, three PB-treated pastures and three control pastures were used. PB pastures were divided into six subplots with one burned rotationally each spring and summer. Control pastures and each PB subplot had a burn interval of 3 yr. Pastures were dragged with 1-m² flannel cloth panels to estimate tick abundance for 4 yr. (2006, 2007, 2009, and 2010). Infestation levels with ticks (i.e., tick burden) and weight for five calves and three cows per pasture were recorded once a month from April to October in 2009, 2010, and 2011. Differences in tick abundance between PB pastures and control pastures were not significant except in 2006 when fewer adult ticks were detected in PB pastures. A total of 13 609 ticks were observed on cattle. Animals on PB pastures had 4 028 (29.6%) ticks whereas 9 581 (70.4%) ticks were on cattle from control pastures. Tick burden was significantly reduced on animals in PB pastures compared to animals in control pastures in 4 out of 6 mo. Significant differences in average daily weight gain of calves in PB and control pastures were not detected. Although differences were not detected in questing tick abundance on pastures, significant reductions of tick burden on cattle in PB-treated pastures indicates that PB can be used to help control ticks in pastures.     

Assessing the impacts of domesticated versus wild ungulates on terrestrial small mammal assemblages at Telperion Nature Reserve,South Africa

Grazing by large mammals alters vegetation physiognomy, consequently changing habitat suitability for small mammal communities. We investigated the response of terrestrial small mammals to grazing by wild and domesticated ungulates at the boundary of a protected area (Telperion Nature Reserve) and surrounding cattle ranches in Mpumalanga, South Africa over two seasons. Fifteen paired grids were set on either side of the boundary fence at which small mammals were trapped in Sherman live traps placed flat on the ground. A total of 11 760 trap nights resulted in the capture of 187 animals belonging to 14 species (11 rodents, two shrews and one elephant shrew). The small mammal communities in grasslands grazed by domesticated or wild ungulates were similar in abundance, species richness, diversity and demographic parameters, likely due to the fact that vegetation structure of the two grazing systems was also similar. We used generalised linear models to show that rock and grass cover were plausible predictors of small mammal abundance in this system. Rock cover showed a positive relationship with small mammal abundance whilst grass cover showed a negative relationship. Our observations suggest that at the scale of our study and with the current stocking densities, wild and domesticated ungulates have similar impacts on the small mammal community.     

Integrating Ranch Forage Production,Cattle Performance,and Economics in Ranch Management Systems for Southern Florida

The presence of grazing cattle near open waterways has created environmental concerns related to the potential for water contamination. In Florida the removal of cattle from grazing landscapes or decreasing stocking density is being investigated as one option to improve the quality of surface water runoff draining into Lake Okeechobee, Florida. The objective of this study was to determine the effects of stocking rate on cow-calf performance, forage availability and quality, and ranch economic performance. Experimental pastures were established on a southern Florida cow-calf operation with stocking rates of 0.58, 1.01, and 1.35 ha·cow^-1 on summer pastures and 0.93, 1.62, and 2.16 ha·cow^-1 on winter pastures, corresponding to high, medium, and low rates, respectively. The study was conducted over 4 consecutive production years. Cow body condition scores (BCS), pregnancy rate, and calf average daily gain were used as measures of animal performance. Forage utilization was estimated by measuring the difference between forage yield inside and outside grazing exclusion cages and forage quality by crude protein and in vitro organic matter digestibility. Forage yield, utilization, and quality were not significantly affected by stocking rate. Although statistically not significant (P = 0.17), cattle in the high stocking rate experienced a numerically greater loss of BCS following the winter grazing period, but stocking rate did not affect pregnancy rate or calf gains. Production (kg weaned calves·ha^-1) was increased (P < 0.01) for a high stocking rate compared with medium and low stocking rates. Overall ranch profitability will decrease as stocking rates decline. Ranch revenues decrease one-for-one as stocking rates decrease. At the same time, unit cow costs increase at an increasing rate as fewer brood cows are left to support the ranch's fixed cost structure.     

Habitat Targets for Imperiled Grassland Birds in Northern Mixed-Grass Prairie

Grassland bird populations are declining faster than any other avian guild in North America, and promotion of favorable habitat conditions in rangeland breeding cores is important for their maintenance. There is much information on associations between breeding grassland songbirds and vegetation attributes. However, previous results have been difficult to translate into management practices due to mismatch between the scale and metrics used in biological sampling and those used in management. Here, we evaluate the response of imperiled grassland bird species to vegetation conditions using metrics and scales accessible to managers. We focus on four species that are experiencing particularly severe population declines: Baird's sparrow (Centronyx bairdii), chestnut-collared longspur (Calcarius ornatus), McCown's longspur (Rynchophanes mccownii), and Sprague's pipit (Anthus spragueii). In 2017 and 2018, we evaluated the abundances of these species within their core distributions in northern Montana. We used temporally replicated point-counts and hierarchical models to estimate abundance and associations with plot-level (9-ha) vegetation conditions while accounting for spatially and temporally variable detectability. Exotic grass encroachment and shrub cover had negative or neutral effects on all species. Birds responded strongly to biomass at this scale, with chestnut-collared longspurs and Sprague's pipit preferring a range of 1 100 kg ha⁻¹ to 1 400 kg ha⁻¹, and McCown's longspurs selecting for the lowest available. Residual grass and litter cover were important for Baird's sparrows. Variable results among species emphasize the need for heterogeneity in vegetation structure and composition at scales larger than the plot. Our results provide guidance for managers interested in improving habitat for these species.     

“n Voorlopige evaluasie van eenjarige,wintergroen weidings met speenlammers,in die Oos‐Kaapse suurveld

A preliminary evaluation of annual, wintergreen pastures using weaned lambs in the eastern Cape sourveld. Animal production and feed availability on oats, vetch and oats/vetch pastures were evaluated under continuous grazing, at three stocking rates, using weaned lambs. The oats and oats/vetch mixture generally produced significantly more available above‐ground phytomass (AAP) than the vetch pasture. No significant differences in AAP or average daily gain (ADG) were measured between stocking rates on the different pastures. The levels of food availability and animal production obtained with the different pastures indicate that oats, vetch and an oats/vetch mixture can be used as annual, wintergreen pastures in the eastern Cape sourveld. However, the stocking rates that were implemented were too low to determine the production potential of the different pastures and an evaluation of the pastures at higher stocking rates is recommended before any recommendation on optimal stocking rates can be made.     

Rangeland Health Assessment: A Useful Tool for Linking Range Management and Grassland Bird Conservation?

Large-scale loss and degradation of North American native prairie coupled with sharp declines in grassland bird populations call for a clear understanding of the effects of livestock production on bird habitat selection. Grassland birds typically select breeding habitat based on a suite of structural and community vegetation features shaped by grazing. Rangeland health indices are a tool for assessing grassland structure and community composition that may offer biologists and range managers common language to achieve grassland bird recovery goals. We used point-count surveys, vegetation measures, and indices of rangeland health to examine bird-habitat relationships on native grassland in southwestern Saskatchewan for 10 grassland bird species. We used an information theoretic approach to compare the support of three hypotheses explaining variation in bird abundance as a function of local vegetation characteristics: bird abundance is best explained by 1) vegetation structure, 2) vegetation structure heterogeneity, or 3) plant community. Vegetation structure variables were present in top-ranking models (i.e., models within four Akaike information criterion units of top model) for eight species and solely comprised top-ranking models for Baird’s sparrow (Ammodramus bairdii), chestnut-collared longspur (Calcarius ornatus), horned lark (Eremophila alpestris), McCown’s longspur (Rhynchophanes mccownii), and savannah sparrow (Passerculus sandwichensis). Structural heterogeneity variables were present in top-ranked models for grasshopper sparrow (Ammodramus savannarum), horned lark (Eremophila alpestris), and western meadowlark (Sturnella neglecta). Plant composition variables solely comprised top-ranking models for clay-colored sparrow (Spizella pallida) and were present in top-ranked models for grasshopper sparrow and vesper sparrow (Pooecetes gramineus). Our results indicate that vegetation structure variables, namely litter mass, vegetation volume, and bare ground cover, best explain variation in bird abundance. Although the rangeland health index received little support as a predictor of bird abundance, vegetation structure components of the index could be used to communicate grazing management guidelines that maintain grassland bird habitat.     

Livestock Management in Red-Billed Chough Feeding Habitat in Great Britain and the Isle of Man

In Great Britain, red-billed chough (Pyrrhocorax pyrrhocorax) breed in discrete populations along the west coast: on Islay and Colonsay, in the Inner Hebrides of Scotland; on the Isle of Man; in Wales; and in Cornwall. Chough are dependent on pastures grazed by sheep or cattle, and their survival therefore depends on sympathetic management of grassland. The Scottish population is in decline, and all other populations are growing or stable. Sixty-three farmers in these regions whose farms were known to support feeding chough were asked questions about their farm management using a structured, questionnaire-based personal interview. Islay farms were significantly larger and had more grazing area, with the lowest stocking densities. Welsh farms had the least cropping area and the smallest number of cattle. Cornwall had the smallest number of sheep per farm. Welsh farms were more likely to not house cattle during winter. Liver fluke in sheep and ticks and tick-borne disease were a higher concern on Islay than other regions, and abortion in sheep was of highest concern on the Isle of Man. Islay farmers applied between 4× and 13× as many synthetic pyrethroid (SP) treatments to cattle per year than farmers at other regions, and the application rate of triclabendazole (TCBZ) to sheep was higher on Islay than other regions. The rate of application of other products, including macrocyclic lactones, did not differ among regions. The study described here shows clear differences in the farm grazing management, in the priority given to animal health problems and in the frequency of application of veterinary parasiticides among four regions that provide feeding habitat for chough in the United Kingdom. These differences suggest that the viability of chough populations might be favored by higher-intensity grazing and low rates of application of veterinary parasiticides of either the TCBZ or SP, or both classes of parasiticides.     

Effects of Cattle Stocking Rates on Nematode Communities in South Florida

Ranch management practices aimed at cattle and pasture vegetation have the potential to impact other animals as well, including nontarget organisms. Soil-inhabiting nematodes are often used as bioindicators of nontarget effects because of their widespread occurrence and their diverse trophic habits and lifestyles. The effect of cattle stocking rates on nematode communities present in the soil was examined at the MacArthur Agro-Ecology Research Center in south-central Florida. Nematode abundance and richness (genera per sample) were not affected (P > 0.10) by cattle grazing in 2 different pasture types (tame grass and native) over three seasons. In general, populations of most nematodes showed strong seasonal responses, varying in numbers from year to year, possibly related to soil moisture levels. In comparison, the cattle stocking rates typically used in south-central Florida had little effect on soil nematodes, which were abundant nontarget organisms in this system.