Habitat selection and breeding ecology of grassland birds in areas managed with fire and grazing

daily survival rate;diversity;fragmentation;grassland birds;habitat selection;heterogeneity;nest-site selection;patch-burn grazing;tallgrass prairie

Duchardt, Courtney ; Miller ; James R.

关键词: daily survival rate;    diversity;    fragmentation;    grassland birds;    habitat selection;    heterogeneity;    nest-site selection;    patch-burn grazing;    tallgrass prairie;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/49443/Courtney_Duchardt.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Conversions of grasslands to row crop agriculture over recent decades have contributed to steep declines in grassland bird populations in the Midwest. On top of habitat loss, the cessation of historic disturbance regimes on remaining grasslands has served to homogenize vegetation structure. Because grassland birds evolved in the context of the interactive disturbances of fire and grazing, their habitat requirements vary over a range of habitat structures. Patch-burn grazing is a management technique that has added benefits over other grassland management because it mimics historic disturbance using fire and grazing to provide a wide range of habitat types for grassland birds.I examined patch-burn grazing as a tool for grassland bird habitat management in the Grand River Grasslands of southern Iowa and northern Missouri. Research began on these sites in 2006, but results from the first phase (2007-2009) indicated patch-burning was not increasing heterogeneity as expected, and that birds were not responding to management. Cattle stocking rates were adjusted in 2010 in hopes of increasing management efficacy. My research utilized data collected between 2010-2013, and was focused on two broad questions: 1) can management adjustments, specifically to stocking rates, improve the efficacy of patch-burn grazing, leading to increased diversity of grassland birds? and 2) how does nest-site selection relate to nest success in three grassland bird species, and what does this mean in the context of management? I found that reduced stocking rates on patch-burned sites increased pasture-level heterogeneity, leading to increased avian diversity on these sites. Among focal species, dickcissels (Spiza americana) selected nest sites with more woody cover, while eastern meadowlarks (Sturnella magna) and grasshopper sparrows (Ammodramus savannarum) selected areas with increased cover of warm-season grasses and litter. Though I observed strong trends in selection, selected traits did not appear to influence nest success, likely due to the diversity of nest predators in this system. Probability of nest survival on patch-burned pastures was comparable to other studies focused on responses of survival to management, and treatment did not strongly influence survival. My research provides evidence that patch-burn grazing can be adjusted for successful use in fragmented landscapes, providing diverse habitat for many species of grassland bird without negatively influencing nest survival.