Factors affecting songbird richness, abundance, and nest survival in riparian forests in a midwestern agricultural landscape
By: by Suzanne Christina Beyeler.
Published: 2009
Language: eng
Number of pages: 174
ISBN-13: 9781109222838
Subjects: Biology, Ecology.; Agriculture, Forestry and Wildlife.
Description: Riparian forests in central Illinois are important breeding habitat for songbirds in an agriculturally dominated landscape. Research has suggested that songbirds are influenced by habitat at multiple scales (i.e., habitat fragmentation, edge effects, exotic species), therefore it is necessary to know which variables are most important so that appropriate management actions can be taken at the appropriate scales. I investigated the relative importance of stream order and patch width on species richness and abundance. I found that species richness was positively associated with patch width but was not related to stream size. However, abundances of certain species were higher in patches adjacent to small order streams indicating that these areas may be important to consider in regional habitat conservation. I also examined the relative importance of various spatial and temporal scales on the nesting success of songbirds. I found that the forest type was the most important variable in determining nesting success of canopy nesters, while landscape-scale factors were most important for shrub-nesting birds. Canopy nesters placed nests more often, and had higher nesting success in, bottomland forests compared to upland forests. Nest success of shrub-nesting birds was negatively associated with the amount of row crops in the surrounding landscape and distance to the nearest forest patch, and positively associated with the amount of forest cover in the landscape and increased length of patch edge. Exotic, invasive vegetation may negatively impact nesting success of songbirds, however the precise relationship is unclear. I examined the influence of  Rosa multiflora and Lonicera maackii on nest success relative to characteristics inherent to all bird nests regardless of nesting substrate (height, concealment, and distance from edge). I found that variables pertaining to the physical location of nests were more important determinants of nest success than use of an exotic shrub as a nesting substrate. Finally, I examined mid-season leaf drop in exotics as a mechanism by which they may negatively influence nesting success of songbirds, using Northern Cardinal (Cardinalis cardinalis) as a focal species. I found that nest concealment in exotic shrubs decreased in midsummer whereas nest concealment in natives remained constant. I also found that nest survivorship of Cardinals decreased in both R. multiflora and L. maackii and slightly increased in native nesting substrates over the nesting season.