Lark Bunting (<i>Calamospiza melanocorys</i>):A Technical Conservation Assessment

The Global and U.S. National Heritage Programs give the lark bunting (Calamospiza melanocorys) a conservation ranking of G5 and N5 respectively, which indicates that the species is widespread and secure. The Canadian National Heritage Program designates the lark bunting as N4, which indicates the species is uncommon but apparently secure with some cause for concern over the longterm (NatureServe 2005). The lark bunting is a Management Indicator Species on the Pawnee National Grassland, which is managed by the Rocky Mountain Region (Region 2) of the USDA Forest Service (USFS). A recent study suggests that lark bunting populations on the Pawnee National Grassland may be declining (Yackel Adams et al. in revision), but the supporting data are not conclusive. Our matrix model suggests that survival of adult lark buntings has the greatest impact on population growth; adult survival rate data are needed in the Pawnee and other areas of its range to validate these estimations. Within Region 2, the greatest threats to lark buntings include habitat loss and habitat fragmentation due to conversion of native grassland to cropland, urbanization, and oil and gas extraction. The World Wildlife Fund classifies most breeding habitats of lark buntings as critical or endangered, with conversion to cropland being the major cause of habitat loss. While lark buntings will nest in some agricultural fields, activities such as plowing, tilling, discing, mowing, and use of pesticides can be very harmful during the nesting period. Human population growth, particularly along the Front Range of Colorado, will likely put increasing demands on lark bunting habitat over the next several decades as grassland is converted to a suburban environment. Current and future increases in oil and gas extraction will continue to fragment and degrade lark bunting habitat in Wyoming and Colorado, and the impacts of these activities will need to be assessed. Heavy grazing by cattle in shortgrass prairie can be detrimental to lark buntings as it reduces the cover required for nesting. Conversely, the lack of grazing in some taller grasses limits the number of lark buntings found in that habitat. Management of grasslands involving moderate grazing and prescribed fire to maintain the mosaic habitat typical of native prairie prior to European settlement would benefit the lark bunting as well as other grassland species. Protection of large tracts of land from agricultural development would help to limit habitat fragmentation and potentially lessen the impacts of nest predation and brood parasitism on lark buntings. Most lark bunting habitat is privately owned, a fact that is unlikely to change in the future. Therefore, landowner incentive programs (e.g., Conservation Reserve Program) and partnerships among conservation organizations, government agencies, and landowners will be needed to increase and preserve lark bunting habitat in the future. On the wintering grounds of the lark bunting, outside of Region 2, potential threats include habitat loss due to urbanization and cropland conversion and habitat degradation in the form of woody species encroachment onto playas. Playas are important areas for feeding and roosting in much of this species’ winter range. Little research has examined lark bunting wintering ecology and the threats specific to its conservation. Study of the impacts of habitat modifications on wintering grounds should be a priority for this species.

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