Nest-Site Fidelity in Grassland Birds on Mowed Versus Unmowed Areas on a Reclaimed Surface Mine

Abstract

We monitored return rates of 324 color-banded Ammodramus savannarum (Grasshopper Sparrow), 138 Passerculus sandwichensis (Savannah Sparrow), and 49 Dolichonyx oryzivorus (Bobolink) on mowed and unmowed areas on a reclaimed surface mine during seven breeding seasons. We observed 61 returns among Grasshopper Sparrows, 40 returns among Savannah Sparrows, and 11 returns among Bobolinks. Grasshopper Sparrows and Savannah Sparrows returned to mowed and unmowed areas at about equal rates (21 vs. 18% and 26 vs. 31%, respectively), while Bobolinks returned to unmowed areas at a higher rate than mowed areas (28% vs. 17% respectively). When hatching-year birds were excluded, overall return rates increased slightly for Grasshopper Sparrows and Bobolinks (19 to 20% and 22 to 23%, respectively), but more substantially for Savannah Sparrows (from 29 to 36%). Sixteen of 51 returning Grasshopper Sparrows (31%), 12 of 27 Savannah Sparrows (44%), and 2 of 10 Bobolinks (20%) were observed during multiple years. These observations support previous findings that reclaimed surface mines provide suitable nesting habitat for these species. Early-season mowing did not appear to influence the return rates of Grasshopper Sparrows or Savannah Sparrows, although it may have influenced Bobolink returns.