Browsing by Author "Christopher E. Moorman, Committee Co-Chair"

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Avian Use of Suburban Greenways as Stopover Habitat
(2007-07-31) Kohut, Salina M.; George R. Hess, Committee Co-Chair; Christopher E. Moorman, Committee Co-Chair; Theodore R. Simons, Committee Member
The decline of Neotropical migrant songbirds has called attention to the need for habitat conservation along the entire migratory route, and scientists now recognize the need to conserve stopover habitat in addition to habitat on the breeding and wintering grounds. Greenways are a popular means for accomplishing conservation goals in suburban areas and might provide stopover habitat in urbanizing areas where habitat loss and alteration are accelerating. My study examined the effects of greenway forested corridor width, greenway vegetative characteristics, and adjacent land cover on the species richness and abundance of migrant songbirds during spring and fall migration. I conducted the study to provide city planners with management recommendations for the construction and maintenance of greenways that will benefit migrating songbirds. During spring and fall migration, 2004, and spring migration, 2005, I surveyed birds in 47 segments of public greenway in Raleigh and Cary, North Carolina, USA representing a range of forested corridor widths and adjacent land covers. I also surveyed three reference sites along trails in William B. Umstead State Park, the largest contiguous forested area (2,201-hectares) nearest the study greenways. Migrant species richness was higher in wider greenways in both spring and fall. During spring migration, migrant bird richness and abundance generally increased with tree height and percent hardwood tree composition, and abundance was greater in greenways with more shrub cover. During fall migration, migrants occurred most commonly in greenways with lower canopy cover and higher shrub cover. Although forest-interior migrant richness was not correlated with greenway forest corridor width in either season, they were more abundant in the reference sites than in the greenways during spring and fall. During spring, forest interior migrants were less common in greenways surrounded by more bare earth and pavement cover, both signs of intense development. Though migrants used greenways of all widths, forested corridors wider than 150 m had the greatest overall diversity and abundance of migrants. Therefore, planners should conserve the widest greenway corridors possible. Shrub and ground cover should be retained within the greenway to provide the complex vegetative structure that migrants use. In urbanizing areas, planners can provide stopover habitat for forest-interior migrants by constructing greenways in areas of lower development intensity and by conserving larger parks or reserves in addition to greenways.
Seasonal Relationships Between Birds and Arthropods in Bottomland Forest Canopy Gaps
(2005-02-02) Bowen, Liessa Thomas; Theodore Simons, Committee Member; Richard Lancia, Committee Member; John Kilgo, Committee Member; Daniel J. Robison, Committee Co-Chair; Christopher E. Moorman, Committee Co-Chair
I investigated the influence of arthropod availability and vegetation structure on avian habitat use at the center, edge, and adjacent to forest canopy gaps in 2001 and 2002. I used mist-netting and plot counts to estimate abundance of birds using three sizes (0.13, 0.26, and 0.5 ha) of 7-8 year old group-selection timber harvest openings during four seasons (spring migration, breeding, post-breeding, and fall migration) in a bottomland hardwood forest in the Upper Coastal Plain of South Carolina. I used foliage clipping, Malaise trapping, and pitfall trapping to determine arthropod abundance within each habitat, and I used a warm water crop-flush on captured birds to gather information about arthropods eaten. I observed more birds, including forest interior species, forest-edge species, field-edge species, and several individual species, in early-successional canopy gap and gap-edge habitats than in surrounding mature forest during all seasons. I found a significant interaction between season and habitat type for several groups and individual species, suggesting a seasonal shift in habitat use. Captures of all birds, insectivorous birds, foliage-gleaners, ground-gleaners, aerial salliers, Hooded Warbler (Wilsonia citrina), Northern Cardinal (Cardinalis cardinalis), White-eyed Vireo (Vireo griseus), and Black-throated Blue Warbler (Dendroica caerulescens) were positively correlated with understory vegetation density during two or more seasons. I found relationships between insectivorous birds and leaf-dwelling Lepidoptera, insectivorous birds and ground-dwelling arthropods, foliage-gleaning birds and foliage-dwelling arthropods, and aerial salliers and flying arthropods, as well as between individual bird species and arthropods. Relationships were inconsistent, however, with many species being negatively correlated with arthropod abundance. Coleopteran, Lepidopteran, and Aranid prey items represented the greatest proportions of crop-flush samples during all seasons. Proportional consumption of Coleopteran and Hemipteran prey items was higher than their proportional availability, and consumption of Aranid and Hymenopteran prey items was lower than their proportional availability during all seasons. Individual bird species and guilds consistently consumed similar proportions of certain groups of arthropods from spring through fall migration, with no apparent seasonal shift in diet composition. My research suggests that many species of birds selectively choose mid-successional gap and gap-edge habitat over surrounding mature forest during the non-breeding season, and the creation of small canopy gaps within a mature forest may increase local bird species richness. It is less obvious how arthropod availability affects bird habitat use across seasons. A structurally diverse mosaic of habitat types, including regenerating canopy gaps within a mature forest, may provide valuable habitat for birds and a variety of arthropod prey items across multiple seasons.