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
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/31583 |
| Date | 06 June 2002 |
| Creators | Davis, Dawn M. |
| Contributors | Crawford, John A. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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