Songbird Response To Mixed Ungulate Herd Reduction Through Changes In Vegetation At Sullys Hill National Game Preserve

• Main Author: Walters, Bethany J.
• Format: Text
• Language: unknown
• Published: UND Scholarly Commons 2014
• Subjects: mixed ungulate; mixed ungulate herd reduction; passerines; plant-animal interactions; Royle Poisson Count; temperate deciduous Forest; Bison bison bison; Plains Bison
• Online Access: https://commons.und.edu/theses/1727; https://commons.und.edu/context/theses/article/2728/viewcontent/Walters_und_0156M_10589.pdf

Big game management traditionally focused on single species management with less emphasis, until recently, on community interactions. Sully's Hill National Game Preserve (SHNGP) is a 678 hectare preserve where extirpated Plains bison (Bison bison) were reintroduced along with Rocky Mountain elk (Cervus elaphus) and white-tailed deer (Odocoileus virginianus). These large ecosystem engineers have been managed at varying densities within a fenced area of deciduous woods, wetlands, and native prairie since 1918. Grazing, browsing, and rubbing by ungulates, along with additional refuge management prescriptions (e.g. prescribed fire), shape the understory and midstory and in turn determine which birds will nest and forage in the area. The 2008 SHNGP Comprehensive Conservation Plan recommended a 50% reduction in herd sizes based on vegetation surveys which indicated little forest regeneration. The suspected cause was overbrowsing by ungulates. An ungulate density of 37 ungulates/km2 was reduced to 19 animals/km2. This density has been annually maintained since 2008. The primary objective of this study was to determine if large ungulate reduction has improved forest regeneration with an ensuing increase in bird abundance and diversity. Vegetation and avian surveys were conducted pre-treatment (before three herd reduction) and repeated post-treatment in 2012-2013. Repeat forest surveys revealed a return of regeneration when analyzed using negative binomial regression, but regeneration is lower in grazed areas as compared to ungrazed. Species accumulation curves revealed that species richness is not returning with regeneration in grazed habitat for both upland and bottomland habitat types. Repeat bird surveys of four target species, ovenbirds (Seiurus aurocapilla), yellow warblers (Dendroica petechia), American redstart (Setophaga ruticilla), and red-eyed vireos (Vireo olivaceus) were analyzed for changes in abundance using Royle repeat measures and changes in species diversity using species accumulation curves. Changes ...