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Correlates of Habitat Fragmentation and Northern Bobwhite Abundance in the Gulf Prairie Landscape Conservation Cooperative

2019    Miller, Katherine S.; Brennan, Leonard A.; Perotto-Baldivieso, Humberto L.; Hernandez, F.; Grahmann, Eric D.; Okay, Atiye Z.; Wu, X. Ben; Peterson, Markus J.; Hannusch, Heather; Mata, Jose; Robles, Jaclyn; Shedd, Taylor

The northern bobwhite Colinus virginianus has experienced range-wide declines over the past several decades, primarily due to habitat loss and habitat fragmentation. As northern bobwhite populations continue to decline, there is a need for studies that address the impact of habitat changes on population persistence at multiple spatial scales. Our goal was to assess changes in habitat and land use related to northern bobwhite declines across multiple spatial scales in Texas, Oklahoma, and Louisiana. We determined northern bobwhite trends for 1972-2012 using Breeding Bird Survey data. At the regional scale, we compared northern bobwhite population trends with road density (2000, 2012), human population (1970-2010), and land use (1974-2012). At the county and local scales, we compared class-level landscape metrics between counties with stable and declining northern bobwhite abundances using Student's t-tests. Northern bobwhite populations decreased from 45.95 +/- 1.01 birds/route in 1970 to 11.55 +/- 0.64 birds/route in 2012. Road density and human population increased by 3,331.32 +/- 66.28 m/km(2) and 42,873 +/- 8,687 people/county, respectively. Percent pasture and rangeland was relatively stable, as was percent woodland. Alternatively, the percentage of other land (houses, roads, wasteland) increased. At the county scale, Texas and Oklahoma counties with declining northern bobwhite populations had higher road densities, larger patches of pasture, smaller patches of woodland, and larger patches of cropland compared with stable populations. At the local scale, Texas and Oklahoma counties with declining northern bobwhite populations had less woody cover in smaller patches, and fewer but larger patches of herbaceous and bare ground, compared with populations with stable abundance. Therefore, managers can provide woody cover and reduce cropland effects at the local scale to support stable quail populations; however, the large-scale drivers of northern bobwhite decline, which are human population growth and resulting habitat loss, will be an important aspect of northern bobwhite conservation and management in the future.