Prescribed grazing management can have myriad effects on wildlife, with low to moderate grazing being associated with an increased abundance of some, but not all, grassland birds. Specifically, the abundance of grasshopper sparrows (Ammodramus savannarum) and savannah sparrows (Passerculus sandwichensis) have been shown to be positively associated with both grazed grasslands and grasslands with a higher percentage of native plant cover. However, relatively little work has occurred on these species in California grasslands. Moreover, measures of abundance provide an incomplete assessment of habitat quality for birds. Physiological and morphological measurements can help indicate environmental stress to individual birds, which can then help reveal more information about habitat quality. To examine the effect of native plant abundance on grassland bird stress, we sampled 70 individuals of each sparrow species on 6 California Coastal Prairie rangelands. We took morphological measurements to estimate body condition and took blood samples for heterophil:lymphocyte (H:L) ratios. In order to quantify the amount of native plant cover in a sparrow’s territory, we conducted vegetation surveys using the line-point transect method. We used generalized linear mixed models to assess the relationship between avian physiological markers and native perennial plants, and implications for rangeland management are discussed.