The spatiotemporal interaction between fire and grazing was a key process in the development of North America's grasslands. Restoring interacting fire and grazing may be instrumental in conserving rangeland biodiversity, but a need exists to understand how it affects organisms in highly fragmented grassland landscapes. We examined nest survival of a species of conservation concern, the Eastern Meadowlark (Sturnella magna), in fragmented Midwestern grasslands that varied in the spatial and temporal application of fire and grazing. The patch-burn grazed treatment (i.e., interacting fire and grazing) consisted of burning a different third of a pasture annually. Pastures in the grazed-and-burned treatment were burned in their entirety every third year and both treatments were moderately stocked with cattle. Average daily nest survival rates were similar across treatments (patch-burn grazed: incubation = 0.90 and nestling = 0.93, grazed-and-burned: incubation = 0.90 and nestling = 0.92), but patch-burn grazing resulted in more stable survival rates from year to year, while the grazed-and-burned treatment appeared to create a boom and bust survival cycle (patch-burn grazed range = 12-16%, grazed-and-burned range = 2-31%). Models indicated a treatment-year interaction, nest stage, and woody vegetation most affected the overall probability of nest survival. Nest survival was greatest in 2009 when grazed-and-burned pastures were burned but dropped dramatically the following year in that treatment. Nests had a higher probability of survival during the nestling stage (β = 0.49, se = 0.27), and woody vegetation near the nest resulted in lower survival (β = -0.07, se = 0.04). Parasitism rates were greater in grazed-and-burned pastures and reduced clutch sizes by an average of 0.6 eggs but did not affect the number of chicks fledging per nest. Overall, our findings suggest restoring heterogeneity to fragmented grasslands through patch-burn grazing can positively affect Eastern Meadowlarks by stabilizing nest survival rates over time.
ASJC Scopus subject areas
- Ecology, Evolution, Behavior and Systematics