Whether to use rotational burning or herbicides to manage native sagebrush-grassland may have implications for sage grouse Centrocercus urophasianus, a declining North American ground-nesting bird (as well as other fauna and flora). A study was conducted on native upland sagebrush-grassland at the US Sheep Experiment Station on the Upper Snake River Plains (southeastern Idaho) to evaluate if sagebrush Artemesia control by herbicide spraying and/or burning, affected grouse nest and brood densities.
Sage grouse nest and brood searches were conducted within 34 plots (10 burned; 3 sprayed; 2.5 burned and sprayed, and 18.5 untreated) of 40 acres (16.2 ha) on foot assisted by trained dogs, and by vehicle. Six plots were searched in summer 1964; all 34 in 1965; 16 plots with nests in previous years were searched, plus an additional 460 acres (186.2 ha) of ‘suspected nesting habitat’, in 1966.
Within the study area, 1,311 ha had been sprayed; one area treated in 1964 and others up to five years previously. Burn sites had been burnt by wildfires (1936 to 1957) or in one case subject to a prescribed burn in 1953.
Within each plot, 10 randomly positioned circular plots (37.2 m²), plus one at each nest and brood location, were established to describe vegetation. The following were recorded: number of shrubs (by species); line intercept of shrub crowns along two transects crossing at the plot centre; height of 10 shrubs per species; an estimate of species basal area and litter cover in 10 (30 x 60cm) plots along each transect.
Thirty-two current year nests plus 55 old nests were located.
In 220 acres searched where sagebrush had been herbicide-sprayed, only one new nest was found (in an area sprayed 5 years earlier) in 1964. The area sprayed in 1964 contained one nest that year prior to spraying (plus one from1963). Three old pre-spray nests were found on other areas. No further nesting on the area sprayed in 1964, and the single nest on other sprayed areas suggest that herbicide treatment was detrimental to nesting.
Results from the burned areas were deemed inconclusive: on 200 acres burned in 1957 but not sprayed (greater average shrub cover than untreated areas) three new nests (1 nest/67 acres) were found; (no further data on location/numbers of nests found presented in the original paper).
Sage grouse selected habitats for nesting most like that present in untreated or burned areas (i.e. with higher shrub and forb cover than sprayed areas).
Broods (n=98) used the untreated and burned areas more than the sprayed areas and tended to select habitat with greater than average total shrub cover.
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