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The Center for Native Grasslands Management

Title: The hazards of nesting near shrubs for a grassland bird, the McCown’s Longspur
Year: 1994
Author(s): With, K. A.
Source Title: Condor
Source Type: Journal
pages: 1009-1019
Original Publication: http://  
Abstract: Half of all nests of the McCown’s Longspur (Calcarius mccownii) were depredated in the shortgrass prairie of northcentral Colorado, and almost all nesting failures in this species were attributable to predators, primarily the thirteen-lined ground squirrel (Spermophilus tridecemlineatus). Nests placed beside shrubs were 2-3 times more likely to be depredated than nests associated with other types of vegetation. Half of all nests (n = 28) were associated with shrubs in a moderately grazed pasture, and 80% of these nests were eventually depredated. In contrast, most nests (57%, n = 21) were placed beside cactus in a heavily grazed pasture, which had little shrub cover. Of the 20% of nests placed beside shrubs in this pasture, however, 75% were depredated. Factor analysis of habitat variables measured at several scales around nests generated one factor that significantly explained variation in nest fate. This factor described shrub cover within 1 m of the nest and midgrass cover and degree of heterogeneity (continuity of the shortgtass matrix) at 2 m. Fine-scale (1 m) shrub cover was the most important determinant of predation risk. Nests that were depredated during incubation had six times more shrub cover within 1 m of the nest than nests depredated during the nestling period; successful nests had no measurable (greater than or equal to 5% total cover) shrub cover at this scale. The relationship between shrubs and an increased risk of nest predation is consistent with incidental predation by ground squirrels, which concentrate their activities beneath the cover afforded by shrubs.