Agronomy and Horticulture Department

 

Date of this Version

2009

Comments

A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Doctor of Philosophy, Major: Agronomy (Applied Ecology); Under the Supervision of Professors Larkin A. Powell and Walter H. Schacht
Lincoln, Nebraska: December, 2009
Copyright (c) 2009 Matthew D. Giovanni

Abstract

The prairie ecosystems of the Great Plains region in North America have largely been replaced and fragmented with industrial agriculture and invasive herbaceous and woody plant species. The concurrent and large-scale suppression of wildfire and elimination of grazing by native ungulates may have further decreased the availability and quality of habitat for wildlife. Indeed, 2004 estimates indicate only 30% of historic grasslands in the Great Plains still exist, while the trends of decreased land area enrolled in the Conservation Reserve Program and increased land area in commercial agriculture indicate continued loss of habitat. This decrease in habitat availability continues to cause population declines for most grassland bird species in North America. The Nebraska Sandhills (Sandhills) region is the largest continuous mixed-grass prairie system remaining in North America, and is almost exclusively managed for cattle production with rotational grazing and wild-hay supplementation. The Sandhills are also, however, subject to increasing demands of natural resources while biological data for management and conservation planning is minimal at best.

The Western Meadowlark (Sturnella neglecta) is broadly distributed across the temperate grasslands of central and western North America, but long-term abundance data indicate populations are declining across Nebraska and most of the species’ breeding range. The Sandhills are a potential population source for grassland bird species breeding elsewhere in fragmented, lower-quality habitat, but information on the demographic responses of species to land management in the Sandhills is mostly nonexistent. I sampled from a population of Western Meadowlarks in the central Sandhills from 2006-2008 to understand the relationships between breeding ecology, vegetation structure, and associated land management. Specifically, I report and discuss 1) selection of nest-site habitat by adults as a function of vegetation variables, 2) nest survival as a function of vegetation, researcher-effect, and temporal variables, 3) selection of habitat by fledglings as a function of vegetation variables, and survival of fledglings as a function of climate and temporal variables.

Advisors: Larkin A. Powell and Walter H. Schacht