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1.
ABSTRACT.   No other group of North American birds has declined as precipitously and over so large an area as has the grassland assemblage. In the Flint Hills of Kansas, the largest extant region of tallgrass prairie, annual spring burning of rangeland has largely replaced traditional regimes and natural patterns with longer intervals between burns. I examined effects of burning and low-intensity cattle grazing on abundances of seven bird species at Konza Prairie Research Natural Area in June 2002 and 2003. Every species was affected by fire, with Upland Sandpipers ( Bartramia longicauda ) more abundant, and six species—Grasshopper Sparrow ( Ammodramus savannarum ), Henslow's Sparrow ( A. henslowii ), Dickcissel ( Spiza americana ), Eastern Meadowlark ( Sturnella magna ), Brown-headed Cowbird ( Molothrus ater ), and Bell's Vireo ( Vireo bellii )—either less abundant or absent at sites in the breeding season following a fire. These results demonstrate that annual burning limits the potential of much of the Flint Hills prairie to harbor high breeding densities of many grassland birds. On the other hand, I found a trade-off between immediate and longer-term effects of burning for several grass-dependent species. Grasshopper Sparrows, Henslow's Sparrows, and Eastern Meadowlarks, although more numerous in areas that were not burned the preceding spring, were less abundant at sites burned every 4 yrs than those burned at shorter intervals. In contrast, shrub-dependent Bell's Vireos were more abundant at sites burned every 4 yrs. Upland Sandpipers, Grasshopper Sparrows, and Eastern Meadowlarks were more abundant in grazed areas. Use of alternatives to annual burning could increase habitat heterogeneity by transforming the Flint Hills into a mosaic of regularly, but asynchronously, burned pastures that would better meet the diverse habitat needs of the region's grassland birds.  相似文献   

2.
Abstract. A map of burn severity resulting from the 1988 fires that occurred in Yellowstone National Park (YNP) was derived from Landsat Thematic Mapper (TM) imagery and used to assess the isolation of burned areas, the heterogeneity that resulted from fires burning under moderate and severe burning conditions, and the relationship between heterogeneity and fire size. The majority of severely burned areas were within close proximity (50 to 200 m) to unburned or lightly burned areas, suggesting that few burned sites are very far from potential sources of propagules for plant reestablishment. Fires that occurred under moderate burning conditions early during the 1988 fire season resulted in a lower proportion of crown fire than fires that occurred under severe burning conditions later in the season. Increased dominance and contagion of burn severity classes and a decrease in the edge: area ratio for later fires indicated a slightly more aggregated burn pattern compared to early fires. The proportion of burned area in different burn severity classes varied as a function of daily fire size. When daily area burned was relatively low, the proportion of burned area in each burn severity class varied widely. When daily burned area exceeded 1250 ha, the burned area contained about 50 % crown fire, 30 % severe surface burn, and 20 % light surface burn. Understanding the effect of fire on landscape heterogeneity is important because the kinds, amounts, and spatial distribution of burned and unburned areas may influence the reestablishment of plant species on burned sites.  相似文献   

3.
ABSTRACT.   Although Savannah Sparrows ( Passerculus sandwichensis ) have been well studied across their North American range, few data are available for populations that breed in high-elevation habitats. We collected data over six years on the demography of a population of Savannah Sparrows ( P. s. anthinus ) breeding in alpine tundra and sub-alpine meadows in northern British Columbia, Canada. The mean duration of the breeding season at our site was 45.5 d, and pairs produced a maximum of one brood per season. Clutch sizes varied annually (mean = 4.37, range = 3.90 – 4.71 eggs). Nest fate also varied among years (range = 33 – 92%) due to variation in abiotic (weather) and biotic (predators) conditions. Uncorrected return rates of banded birds were 68% for adults and 17% for juveniles ( N = 22 and 102, respectively). However, when resighting probability was taken into account, apparent annual survival was 75% for adults and 34% for juveniles. Compared to populations at lower elevations, Savannah Sparrows in our study had shorter breeding seasons, fewer broods per season, larger clutches, and higher adult and juvenile return rates. Our results suggest that Savannah Sparrows that breed in high-elevation habitats have adopted a low fecundity, high survival life history strategy that enables their persistence in these challenging environments.  相似文献   

4.
We investigated the ranging behaviour during the breeding season of 18 radiotracked little bustard (Tetrax tetrax) males, a disperse-lekking species inhabiting the cereal pseudo-steppes. The average kernel 95% home range was 60±50 ha and the average cluster 85% area was 17±17 ha. Range structure was as relevant as home range size for explaining the variation in the ranging behaviour of males, which could be partially explained by age, habitat quality and site. Ranging behaviour varied from males defending small and concentrated home ranges with high habitat quality, to males holding larger home ranges composed by several arenas. Our results suggest that social dominance and resource availability may affect ranging behaviour of males during the breeding season. Also, mating systems constraints may play a role on the use of space of males within the lekking ground. The ranging behaviour of a given male may be determined by a tendency to reduce and concentrate the home range as age and social status increase, and several fine-tuning mechanisms adjusting the ranging behaviour to the prevailing environmental or social factors on a given site and year.  相似文献   

5.
Despite the acknowledged importance of prescribed fire in creating northern bobwhite (Colinus virginianus) breeding cover, little research has investigated bobwhite breeding season habitat selection relative to time since fire. In 2016 and 2017, we monitored radio-tagged bobwhite on a 17,000-ha portion of a military installation managed with frequent (every ~3 years) prescribed fires, applied during the growing and dormant seasons. We monitored bobwhite to determine which vegetation characteristics associated with prescribed burning were important to bobwhite breeding season habitat selection at the microsite (i.e., telemetry location compared to nearby random location) and the macrosite scale (i.e., the burn-unit containing the location compared to study area availability). During 2 breeding seasons, we collected 2,315 bobwhite locations and compared percent cover of vegetation, days since burn, basal area, and distance to key landscape features (e.g., stream, wildlife opening) at a subset of microsite locations (301 locations during 2016 and 890 locations during 2017) to paired random locations. At the microsite scale, bobwhite selected lower basal area of hardwoods, greater woody understory cover, greater other (not wiregrass [Aristida stricta]) grass cover, and greater forb cover than at random points. At the macrosite scale, bobwhite selected units with <4.6 m2/ha basal area (combined hardwoods and pines) in 2016 and units with <9.2 m2/ha basal area in 2017. At the macrosite scale, bobwhite selected for areas burned in the dormant season of the same year, avoided areas burned in the growing season of the same year, and used other times since last burn categories proportionate to their availability. The selection for a low basal area at both scales indicates prescribed fire effects would be limited by shading from dense overstory, and the shrubs, grasses, and forbs that provide essential cover for bobwhite during the breeding season will not develop. In lower productivity soil regions similar to our study area, we advise that thinning operations set target basal areas below 10 m2/ha to create and maintain breeding season habitat for northern bobwhite. © 2019 The Wildlife Society  相似文献   

6.
Bimonthly changes in home range size of seven mature roe deer Capreolus capreolus L. females were analysed over one year. Great stability of home range size and high site fidelity was common to all females, which remained bimonthly within areas of 6.1–20.8 ha. Two groups of females could be identified on the basis of bimonthly variations in their home range sizes: females with larger areas (LHR females), who decreased their ranges in the birth season only, and females with smaller home ranges (SHR females), who increased significantly their home ranges during the rut. The most likely explanation is that the areas inhabited by SHR females included high-quality food resources allowing survival even in small home ranges. In the rut, SHR females may have expanded their ranges to increase mating opportunities.  相似文献   

7.
Prescribed fire is an increasingly important management tool for eastern deciduous forests, but relativity little is known about the direct effects of fire on the eastern box turtle (Terrapene carolina carolina). We used very high frequency (VHF) transmitters to monitor mortality, movement, and spatial ecology of 118 box turtles in response to 17 prescribed fires across 4 seasons and 3 sites in east Tennessee, USA, during 2016–2018. Annual survival of box turtles that experienced a prescribed fire event was lower (0.87 ± 0.04 [SE]) than turtles that did not (0.98 ± 0.01) and was negatively correlated with fire intensity, fire temperature the turtle experienced, and litter depth. All prescribed fire-related mortalities occurred during the early (Apr–May, n = 5) or late growing season (Sep–Oct, n = 1). Fourteen percent of box turtles we captured exhibited damage to their carapace from previous fire events. Box turtles that survived prescribed fires were in microsites that did not burn, moved to unburned areas during the fire, or burrowed following ignition. Home range size was similar before and after burns and sinuosity of movements did not differ in burned or unburned areas. Our results indicate that though box turtles are susceptible to prescribed fire during their active season, they have behavioral and physical traits that reduce the direct effects of prescribed fire. Prescribed fire practitioners should be aware of the risks of fire, particularly during the active season. We suggest managers consider altering prescribed fire intensity, seasonality, and firing pattern to minimize risk of direct effects where box turtles are of concern. © 2020 The Wildlife Society.  相似文献   

8.
The daily locations of socially active male grey seals were recorded during three successive breeding seasons on North Rona (Outer Hebrides, Scotland). Areas of occupancy were defined for 38 individually identified males. Socially active males showed a high degree of site fidelity, determined from the overlap of areas and distance moved by individuals between seasons. The degree of site fidelity displayed by individuals was not related to measures of individual mating success, dominance, date of arrival to the colony, length of stay at the colony or changes in these values between seasons. As both male and female grey seals display site fidelity on N. Rona, individual recognition of potential opponents and mates is possible. There is also potential for the production of full sibling offspring in successive seasons.  相似文献   

9.
Changes in structural and compositional attributes of shinnery oak (Quercus havardii Rydb.) plant communities have occurred in the twentieth century. These changes may in part relate to altered fire regimes. Our objective was to document effects of prescribed fire in fall (October), winter (February), and spring (April) on plant composition. Three study sites were located in western Oklahoma; each contained 12, 60 × 30‐m plots that were designated, within site, to be seasonally burned, annually burned, or left unburned. Growing season canopy cover for herbaceous and woody species was estimated in 1997–1998 (post‐treatment). At one year post‐fire, burning in any season reduced shrub cover, and spring burns reduced cover most. Winter and annual fires increased cover of rhizomatous tallgrasses, whereas burning in any season decreased little bluestem cover. Perennial forbs increased with fall and winter fire. Shrub stem density increased with fire in any season. Communities returned rapidly to pre‐burn composition with increasing time since fire. Fire effects on herbaceous vegetation appear to be manifested through increases in bare ground and reduction of overstory shrub dominance. Prescribed fire can be used as a tool in restoration efforts to increase or maintain within and between community plant diversity. Our data suggest that some plant species may require or benefit from fire in specific seasons. Additional research is needed to determine the long‐term effects of repeated fire over time.  相似文献   

10.
Populations of Bachman's Sparrows (Peucaea aestivalis) have declined range‐wide since the late 1960s. Populations at the periphery of their range have exhibited some of the steepest declines, and these sparrows are now rare or extirpated over much of the northern extent of their historical range. To better understand the spatial ecology of Bachman's Sparrows in this region of decline, we examined microhabitat selection and determined the home range sizes of radio‐tagged male Bachman's Sparrows (= 37) in the Coastal Plain of North Carolina in 2014 and 2015. From April to July, we located males 1–2 times daily for 5–6 d per week. We measured vegetation structure in home ranges using 5‐m‐radius plots centered on a subset of 10 randomly selected telemetry locations as well as in available unused locations 50 m and in a random direction from each telemetry location. Mean size of home ranges (7.9 ha) was larger than estimates reported in most previous studies, with differences among studies possibly due, at least in part, to differences in the characteristics of habitats where studies were conducted. The home ranges of Bachman's Sparrows in our study had greater densities of woody and dead vegetation than unused areas. Although generally considered detrimental to the presence of Bachman's Sparrows, the presence of some woody vegetation in frequently burned (i.e., ≤ 3‐yr return interval) longleaf pine (Pinus palustris) communities like those in our study may be important in providing song perches for males and cover from attacking predators. Bachman's Sparrows in our study showed clear selection for several vegetation characteristics linked to frequent fire. Management strategies that approximate historical fire regimes in longleaf pine ecosystems should continue to be promoted as essential tools for the conservation of Bachman's Sparrows.  相似文献   

11.
ABSTRACT Buff-breasted flycatchers (Empidonax fulvifrons) are rare in the United States due to a >90% reduction in breeding distribution. Previous authors have implicated fire suppression in montane woodlands as the underlying cause of population declines and range contraction. We examined the effect of fire suppression on population declines of buff-breasted flycatchers by comparing both presence and abundance of flycatchers in areas with and without evidence of recent fire in 9 mountain ranges in southern Arizona, USA. We also replicated previous survey efforts conducted in 1980–1983 and 1995–1996 to determine population trajectory. Twenty-two (63%) of 35 survey routes had negative trends, and the average slope of the declines was −0.105 (10.5% annual decline). The number of buff-breasted flycatchers detected at a survey point was positively associated with severity of recent fires, and flycatchers were particularly associated with areas that had evidence of high-severity surface fire. However, we failed to detect flycatchers in 5 canyons that recently burned, which suggests one or more of the following: 1) fire suppression is not the cause (or is not the main cause) of population decline and range contraction, 2) flycatchers do not colonize burned areas until >10 years postfire, 3) low- or medium-severity fires are insufficient to make fire-suppressed areas suitable for breeding flycatchers, or 4) local recruitment and immigration are insufficient to allow buff-breasted flycatchers to expand into recent firerestored areas. Continued suppression of high-severity forest fires in the southwestern United States may eventually result in the extirpation of buff-breasted flycatchers. A landscape that includes a mosaic of recently burned and unburned forest patches appears to be most suitable for buff-breasted flycatchers. Prescribed burning is unlikely to help restore flycatcher populations unless burns are of high severity, conditions typically avoided during prescribed burns for safety reasons.  相似文献   

12.
We measured for the first time movement, home range and site fidelity of the protected and endemic Australian fish weedy seadragon Phyllopteryx taeniolatus. Ninety-two individuals were identified using visual implant fluorescent elastomer and studied over a one-year period. Identified animals remained at the same site over the year within limited home ranges. These home ranges and the movement patterns recorded were independent of sex although movement to shallow sheltered waters to hatch the young was observed at the end of the breeding season for some pregnant males. The site fidelity and restricted home range of the weedy seadragon, as well as the reproduction-related movement have implications for effective management of this protected species.  相似文献   

13.
Western Sandpipers Calidris mauri are the most numerous shorebird species in the San Francisco Bay estuary during winter. A sample of 106 Western Sandpipers was captured in mist nets and radio-marked with 1-g transmitters to examine their wintering site fidelity and movements. Differences in distances moved, home range extent and core area size were examined by age, sex, season, site, time of day and tide. All birds remained in the south San Francisco Bay region during winter and exhibited strong site fidelity, with a mean home range of 22.0 km2 or only 8% of the study area. First-year birds had larger home ranges (26.6 ± 3.6 km2) than adults (17.2 ± 2.5 km2) in winter, but home range sizes of males and females were not significantly different in any period. Home range sizes were similar between seasons, but core areas were smaller in spring (6.3 ± 1.2 km2) than in early (9.6 ± 4.0 km2) or late (11.6 ± 1.6 km2) winter. Movements and home range size were similar for radio-marked birds located during day and night. The high degree of regional and local site fidelity demonstrated that the mixture of natural mud fiats and artificial salt ponds in southern San Francisco Bay provided sufficient resources for large wintering populations of Western Sandpipers.  相似文献   

14.
A comprehensive understanding of spatiotemporal ecology is needed to develop conservation strategies for declining species. The king rail (Rallus elegans) is a secretive marsh bird whose range historically extended across the eastern United States. Inland migratory populations have been greatly reduced with most remaining populations inhabiting the coastal margins. Our objectives were to determine the migratory status of breeding king rails on the mid‐Atlantic coast and to characterize home range size, seasonal patterns of movement, and habitat use. Using radiotelemetry, we tracked individual king rails among seasons, and established that at least a segment of this breeding population is resident. Mean (±SE) home range size was 19.8 ± 5.0 ha (95% kernel density) or 2.5 ± 0.9 (50% kernel density). We detected seasonal variation and sex differences in home range size and habitat use. In the nonbreeding season, resident male home ranges coincided essentially with their breeding territories. Overwintering males were more likely than females to be found in natural emergent marsh with a greater area of open water. Females tended to have larger home ranges than males during the nonbreeding season. We report for the first time the use of wooded natural marsh by overwintering females. Brood‐rearing king rails led their young considerable distances away from their nests (average maximum distance: ~600 ± 200 m) and used both wooded natural and impounded marsh. King rails moved between natural marsh and managed impoundments during all life stages, but the proximity of these habitat types particularly benefitted brood‐rearing parents seeking foraging areas with shallower water in proximity to cover. Our results demonstrate the importance of interspersion of habitat types to support resident breeders. Summer draining of impounded wetlands that are seasonally flooded for wintering waterfowl allows regrowth of vegetation and provides additional habitat at a critical time for wading birds.  相似文献   

15.
The ability to be faithful to a particular area or site was analysed in the shanny Lipophrys pholis. Using passive integrated transponders, adults from a population of L. pholis at Cabo Raso, Portugal, were followed over a period of 3 years. The findings showed that site fidelity is a consistent behaviour during the breeding season with specific breeding males being found only in particular sectors within the area, and in specific nests throughout the years. The fact that, in general, L. pholis individuals were absent from the study area during the non‐breeding season and breeding males were recorded returning to the same nests and sectors for consecutive breeding seasons suggests that they have developed excellent homing abilities. Translocation data corroborate this idea showing that breeding males successfully returned to their nests after a displacement of >100 m. Altogether, these findings highlight the relevance of life‐history traits (e.g. nesting) in the conditioning of site fidelity and homing for this species of rocky intertidal fish, and more importantly, provide evidence for the need of a well‐developed navigational system.  相似文献   

16.
Canada's federal recovery strategy for boreal woodland caribou (Rangifer tarandus caribou) classifies areas burned by forest fire as disturbed habitat. This assignment of fire as a disturbance has potential economic and social implications across Canada, and influences plans and actions to achieve caribou conservation and recovery. Previous researchers have reported caribou avoid burned habitat, but these studies did not typically consider unburned residual patches within fire perimeters. Additionally, the implications of burned habitat on individual caribou survival is unclear. We examined resource selection by boreal woodland caribou of burns, and unburned residual patches, using global positioning system (GPS) locations for 201 caribou across 6 caribou populations in Alberta, Canada. We also examined if burned habitat affected the survival of adult female caribou. Caribou avoided burns and unburned residual patches. Increased use of burned habitats, however, did not lower the survival of adult caribou. Collectively, these results provide evidence to support current assertions that burns, and the embedded unburned residual patches are not preferred caribou habitat and increase our understanding of the implications of forest fire for caribou vital rates. Our investigation offers important information about the role of forest fire in caribou ecology and enhances the identification of disturbed habitat under recovery strategy guidelines to effectively address caribou population declines. © 2021 The Wildlife Society.  相似文献   

17.
Black‐throated Sparrows (Amphispiza bilineata) are common breeding birds throughout the desert regions of North America and can be considered nest‐site generalists. Information about how spatial (e.g., vegetation) and temporal factors influence nest survival of these sparrows is lacking throughout their range. Our objective was to examine the spatial and temporal factors associated with nest survival of Black‐throated Sparrows at the nest and nest‐patch scales in the predator‐rich environment of the northern Chihuahuan Desert of New Mexico. We used a logistic‐exposure model fit within a Bayesian framework to model the daily survival probability of Black‐throated Sparrow nests. Predation was the leading cause of nest failure, accounting for 86% of failed nests. We found evidence of negative associations between nest survival and both vegetative cover above nests and shrub density within 5 m of nests. We found no support for other habitat covariates, but did find strong evidence that daily survival rate was higher earlier in the breeding season and during the egg‐laying stage. A decline in nest survival later in the breeding period may be due to increased predator activity due to warmer ambient temperatures, whereas lower survival during the incubation and nestling stages could be a result of increased activity at nests. A generalist approach to nest‐site selection may be an adaptive response to the presence of a diverse assemblage of nest predators that results in the reduced influence of spatial factors on nest survival for Black‐throated Sparrows.  相似文献   

18.
One of the largest and rarest Bebb willow (Salix bebbiana) communities in the United States occurs at Hart Prairie, Arizona. Low recruitment of the willow over the past several decades has been linked to inadequate soil water content for seed germination and seedling establishment. We tested a hypothesis that a prescribed burn would reduce biomass of and evapotranspiration by herbaceous plants, thereby increasing soil water content. Three treatments (unburned control, early‐growing season burned, late‐growing season burned) were applied in year 2001 to replicated plots in fern‐ and grass‐dominated herbaceous communities. Soil water content (0–30 cm) was measured weekly in plots during the 2001, 2002, and 2003 growing seasons. Both early‐ and late‐season burning reduced herbaceous biomass in the fern‐dominated community in 2002 and 2003 and reduced biomass in the grass‐dominated community in 2002 but not in 2003. Soil water content increased for approximately four weeks in 2001 following the early‐season burn, but the early‐season and late‐season burns reduced soil water content in both communities over much of the 2002 and 2003 growing seasons. Thus, early‐season burning may benefit willow seed germination by increasing soil water content immediately following burning but be detrimental to germination in the second and third growing seasons after burning because of drier soil. Large temporal variation in the effect of prescribed burning on soil water content will complicate the use of fire as a restoration tool to manage soil water available for threatened plants such as Bebb willow and for recharge of groundwater.  相似文献   

19.
Sun  Yuxin  Wu  Jianping  Shao  Yuanhu  Zhou  Lixia  Mai  Bixian  Lin  Yongbiao  Fu  Shenglei 《Ecological Research》2011,26(3):669-677
Prescribed burning is a common site preparation practice for forest plantation in southern China. However, the effects of prescribed burning on soil microbial communities are poorly understood. This study examined changes in microbial community structure, measured by phospholipid fatty acids (PLFAs), after a single prescribed burning in two paired vegetation sites in southern China. The results showed that the total amount of PLFA (totPLFA) was similar under two vegetation types in the wet season but differed among vegetation type in the dry season, and was affected significantly by burning treatment only in the wet season. Bacterial PLFA (bactPLFA) and fungal PLFA (fungPLFA) in burned plots all decreased compared to the unburned plots in both seasons (P = 0.059). Fungi appeared more sensitive to prescribed burning than bacteria. Both G+ bacterial PLFA and G bacterial PLFA were decreased by the burning treatment in both dry and wet seasons. Principal component analysis of PLFAs showed that the burning treatment induced a shift in soil microbial community structure. The variation in soil microbial community structure was correlated significantly to soil organic carbon, total nitrogen, available phosphorus and exchangeable potassium. Our results suggest that prescribed burning results in short-term changes in soil microbial communities but the long-term effects of prescribed burning on soil microbial community remain unknown and merit further investigation.  相似文献   

20.
Populations on the limits of species’ distribution can show different behavioral adaptations to strong ecological pressure than in the central part of the range. We investigated space use patterns of alpine mountain hare (Lepus timidus) at two areas on the southern edge of the species’ range. We monitored 34 hares between 2005 and 2008, estimating home range size, overlap, and site fidelity, and compared our results with space use in Scottish and North-European populations. Home ranges of mountain hares did not differ between two study areas with different habitat types. Subadult animals used larger ranges than adults and both age groups reduced home range size in autumn, a period that might be critical for hares due to changes in diet and/or high energy expenditure during the previous breeding season. Home ranges in these alpine populations were smaller than in Scandinavian populations but within the range of populations in different habitat types in Scotland. Seasonal home ranges overlapped considerably, but differed among the sexes: male–female overlap was higher than same sex (male–male and female–female) spatial overlap. Seasonal shifts of home ranges were small, and site fidelity remained high over the seasons, suggesting that resource distribution remained constant throughout the year and that the knowledge of an intensively frequented area is an important element of habitat quality. We concluded that habitat structure and availability of mates interact in affecting mountain hare space use in alpine habitats.  相似文献   

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