Document Type

Thesis - Open Access

Award Date

2022

Degree Name

Master of Science (MS)

Department / School

Natural Resource Management

First Advisor

Joshua Stafford

Keywords

cereal rye, cover crop, grassland, litter, management, species of greatest conservation need

Abstract

The tallgrass prairie of North America has changed drastically since colonial settlement, with up to 99% of this region converted for agriculture and other land-uses. Concurrent with grassland conversion, grassland birds have experienced the most extreme, consistent, and widespread population declines of any avian guild. Agricultural lands in the U.S. Midwest were able to provide adequate habitat for several bird species until the 1950’s; however, altered and intensified management practices have degraded much of remaining suitable habitat and undermined ecosystem functions. Consequently, many grassland birds have been identified as Species of Greatest Conservation Need (SGCN) in many State Wildlife Action Plans. The use of cover crops is a re-emerging practice in sustainable agriculture that may have beneficial impacts on grassland birds. Cover crops are widely accepted to have numerous agricultural benefits, but the potential to provide further ecological benefits, such as provision of habitat and resources for avifauna, are poorly understood. The goal of my study was to evaluate the use of cover crops by avifauna relative to perennial cover and fallow/row crop systems in southeastern Iowa, where cover crops and avifauna were suitably abundant. I accomplished this using two approaches: 1) I evaluated and compared community compositions among field types using permutational analysis of variance (PERMANOVA) and non-metric multidimensional scaling (NMDS) diagnostics and 2) I measured and quantified various microhabitat characteristics and used these to model variation in 4 avian population metrics (i.e., total avian abundance, total avian richness, abundance of avian SGCN, and richness of SGCN). I documented 66 bird species during 2019 and 2021, 22 of which are considered Iowa SGCN. Results of PERMANOVA and NMDS suggested cover crops harbored a bird community that overlapped in abundance and richness with row crops but tended to be broader and support some species otherwise absent in croplands; however, cover crops did not completely overlap with habitat provided by perennial cover. Of the variables intended to predict avian population metrics, coverage by rye, litter residue cover, and litter depth appeared to be most influential. For example, a model of total avian abundance suggested a 10% increase in the mean area covered by litter predicted an increase of 9.4 birds. Management practices that promote litter accumulation and structure in cover cropped fields, such as later termination times, may improve cover crop fields for grassland bird species. My results may be used to develop planning tools and management strategies for resource managers, farmers, and biologists, and, when integrated with other sustainable agricultural practices, promote the conservation of imperiled birds.

Library of Congress Subject Headings

Grassland birds -- Conservation -- Iowa.
Grassland birds -- Ecology -- Iowa.
Cover crops -- Iowa.
Rye -- Iowa.

Number of Pages

82

Publisher

South Dakota State University

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Rights Statement

In Copyright