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Small mammal and bird abundance in relation to post-fire habitat succession in mountain big sagebrush (Artemisia tridentata ssp. vaseyana) communitiesHolmes, Aaron L. 28 December 2010 (has links)
Fire is an important disturbance mechanism in big sagebrush (Artemisia
tridentata) communities, yet little is known about wildlife population dynamics during
post-fire habitat succession. I estimated the abundance of small mammals and birds in
relation to fire history in mountain big sagebrush (A.t. spp. vaseyana) communities on the
Sheldon National Wildlife Refuge in the northwestern Great Basin, USA. I employed a
chronosequence approach that took advantage of multiple wildfires that had occurred in
similar plant communities between 7 to 20 years prior to sampling.
Belding’s ground squirrel (Spermophilus beldingii) were approximately 10 times
as abundant in burned areas relative to adjacent unburned habitat regardless of the
number of years since a burn occurred. Deer mouse (Peromyscus maniculatus) was more
abundant on more recently burned sites, but not at sites closer to full vegetation recovery.
Great basin pocket mouse (Perognathus parvus), sagebrush vole (Lemmiscus curtatus),
and least chipmunk (Tamius minimus) abundance did not vary as a function of fire
history, but some variance was explained by habitat features such as rocky areas and the
canopy characteristics of sagebrush.
Bird diversity was higher in unburned habitats irrespective of the number of years
of recovery out to 20 years. Nine of the 12 most widely occurring species of birds in the
study have population densities influenced by fire or post-fire habitat succession to at
least 13 to 20 years following a burn. Sage Sparrow (Amphispiza belli), Black-throated
Sparrow (Amphispiza bilineata), and Spotted Towhee (Pipilo maculatus) occurred at
relatively low densities and were nearly restricted to unburned habitats. Green-tailed
Towhee (Pipilo Chlorurus), Gray Flycatcher (Empidonax wrightii), American Robin
(Turdus migratorius), and Brown-headed Cowbird (Molothus ater) occurred at lower
densities in burned areas than adjacent unburned areas although the relationship was not
strong for the latter two species. The magnitude of the difference in density between
burned and unburned sites within a landscape diminished with the number of years of
vegetation recovery for Green-tailed Towhee. Brewer’s Sparrow (Spizella brewerii)
occurred at lower densities relative to adjacent habitat in the most recent burn, but
occurred at higher densities after 20 years of habitat succession, suggesting a positive
response with a multiple decade lag period. Horned Lark (Eremophila alpestris) and
Vesper Sparrow (Pooecetes gramineus) respond positively to fire, but densities were
similar to unburned areas after 20 years of habitat succession.
An ordination analysis captured 86% of the variation in 12 bird species with 3
orthogonal axes. My research demonstrates that strong community structure exists for
birds associated with mountain big sagebrush habitats, and that fire influences
community structure for multiple decades. / Graduation date: 2011 / Access restricted to the OSU Community at author's request from Dec. 22, 2010 - Dec. 22, 2011.
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The Impacts of Feral Horses on the Use of Water by Pronghorn on the Sheldon National Wildlife Refuge, NevadaGooch, Amy Marie 01 December 2014 (has links) (PDF)
Feral horses occupy 31.6 million acres throughout western North America. Feral horses share similar habitats with a wide range of animal species, including pronghorn. Since horses are larger and often more aggressive than other animals of this region, they are generally socially dominant over all other native ungulate species. Pronghorn share water sources with horses in areas where both occur. In situations where horses exclude pronghorn from water, pronghorn fitness may be impaired, especially during the hottest months of the year when water is limited. The purpose of this study was to investigate interference competition between pronghorn and feral horses at water sources. During spring and summer 2010-11, we placed motion-sensitive cameras at water sources across the Sheldon National Wildlife Refuge in northwest Nevada. Cameras were used to examine the overlap of water use by pronghorn and horses and to determine the occurrence of spatial or temporal partitioning of water between these species. Additionally, we made direct observations of horses and pronghorn at high-use water sources to record the occurrences and outcomes of pronghorn/horse interactions as well as differences in pronghorn behavior in the presence and absence of horses. Pronghorn spent more time on vigilance behavior and less time foraging or drinking in the presence of horses than in their absence. Nearly half of pronghorn/horse interactions at water resulted in pronghorn exclusion from water. Our data also suggest that temporal partitioning of water between horses and pronghorn on an hourly basis may be occurring.
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Breeding season habitat use and response to management activities by greater sage-grouse on Sheldon National Wildlife Refuge, NevadaDavis, Dawn M. 06 June 2002 (has links)
Greater Sage-Grouse (Centrocercus urophasianus) have experienced declines
throughout their range over the last 50 years. Long-term declines in sage-grouse
abundance in Nevada and Oregon have been attributed to reduced productivity. From
1995-1997, sage-grouse production on Sheldon National Wildlife Refuge (SNWR),
Nevada was greater compared to Hart Mountain National Antelope Refuge (HMNAR),
Oregon. Specific causes for the difference were unknown. Thus, the objectives were to:
1) Determine sage-grouse breeding season habitat use (especially with regard to wildfire)
on SNWR; 2) Evaluate reproductive parameters to discern differences between SNWR
and HMNAR; 3) Compare habitat components which may relate to differences in sage-grouse
reproductive success on SNWR and HMNAR; and 4) Establish hematological
and serum chemistry reference ranges for sage-grouse hens to assess physiological
condition.
Cover type was important in selection of nest sites at SNWR; however, nest cover
did not affect nesting success and nest-site selection was not related to experience.
Vegetative characteristics at successful nest sites were similar to unsuccessful nests but
nest sites had greater amounts of tall residual grass (���18 cm) and medium height shrub
cover (40-80 cm) than at random sites. Broods used areas with greater forb cover than
random sites, indicating use was influenced by availability of forbs.
Plant communities in wildfire and associated control sites did not differ
appreciably in species composition. Although burning had little stimulatory effect on
total forb cover 10-12 years post-burn, alteration of the sagebrush community did not
limit sage-grouse use for successful nesting and brood-rearing. Fire did not negatively
impact arthropod abundance.
Differences in habitat use and sage-grouse productivity between SNWR and
HMNAR may be related to differences in forb availability. Forb cover was greater at
HMNAR than at SNWR for all cover types. Correspondingly, home range size for sage-grouse
broods was greater on SNWR than at HMNAR. Nutrient analysis of forbs
indicated higher crude protein, potassium, and magnesium levels at HMNAR than at
SNWR; however, these nutrients are not likely to be deficient in most sage-grouse diets.
Thus sagebrush-steppe communities supporting these forbs likely meet the dietary
nutritional requirements of sage-grouse. Although blood calcium and uric acid levels
were greater in sage-grouse hens on HMNAR than at SNWR, differences were attributed
to capture date. Furthermore, physiological condition did not affect a hen's ability to nest
successfully, nor was condition related to a hen's ability to recruit chicks to 1 August.
Causes of sage-grouse decline are varied, but ultimately they are habitat based.
Comparisons of reproductive parameters and habitat evaluations, combined with sage-grouse
physiology data, may provide insight into habitat differences between study areas
not previously recognized. Land management practices (e.g., prescribed fire) which
recast the balance of native herbaceous species in degraded big sagebrush communities,
may be necessary in the restoration of sagebrush-steppe ecosystems, and ultimately, the
recovery of sage-grouse populations. / Graduation date: 2003
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