Browsing by Subject "Songbirds"

Now showing 1 - 3 of 3
  • Thumbnail Image
    Item
    Molecular phylogenetics of the New World blackbirds (Icteridae)
    (2012-12) Powell, Alexis Frederick Leo Alvey
    The New World blackbirds (Icteridae) are among the best known songbirds, both through exemplar species, such as the Red-winged Blackbird (Agelaius phoeniceus), and collectively, as a model clade in studies of morphological, ecological, and behavioral trait evolution. Knowledge of phylogeny is a prerequisite for comparative studies and the basis for systematic classification, yet there has been no comprehensive analysis of blackbird phylogeny. In Chapter 1, I present the phylogeny of the grackles (Quiscalus spp.) inferred from cytochrome b and ND2 gene sequences. A primary concern was determining the relationships of the extinct Slender-billed Grackle (Q. palustris) and Q. nicaraguensis, which is unusual among grackles for its restricted geographic range. I found the Slender-billed Grackle to be most closely related to one of two major haplotype clades of Q. mexicanus, the other being sister to Q. major. Q. nicaraguensis appears sister to Q. lugubris. I also found that Q. mexicanus, niger, and lugubris contain deeply-divergent lineages. In Chapter 2, I present a method for partitioning whole mitochondrial genome sequences to optimize model-fitting during phylogenetic analyses. Because standards for rigorous phylogenetic analyses of mitogenomes were lacking, developing such a method was a prerequisite for analyzing the mitogenomes of a clade of South American endemic blackbirds. I found that the most useful categories for partitioning were codon position, RNA secondary structure pairing, and the coding/noncoding distinction, and that a scheme with nine data groups outperformed all of the more complex alternatives (up to 44 data groups) that I tested. In Chapter 3, I present the first comprehensive species-level phylogeny of the Icteridae. By using mitochondrial gene sequences from all ~108 currently-recognized species, together with strategic sampling of 4 nuclear loci and whole mitochondrial genomes at the generic level, I was able to resolve most relationships with high confidence. The best-resolved phylogeny is consistent with strongly-supported results of past studies, but it also contains many novel robustly-resolved inferences of relationship, including some unexpected placements of taxa that had not been included in previous molecular phylogenies, resolution of the relationships among major subclades within Icteridae. I suggest taxonomic revisions based on those results.
  • Thumbnail Image
    Item
    Responses of songbirds and small mammals to harvests of native grasslands for biofuels in Western Minnesota
    (2014-01) Dunlap, Robert Michael
    Some grassland birds and small mammals exhibit changes in abundance following vegetation removal in the previous year, but it is unknown to what extent these organisms respond to harvests of diverse, native grasslands. This thesis examines the effects of harvesting such grasslands on songbirds and small mammals, representing an important step in evaluating the conservation value of grasslands used for biofuel harvest. I analyzed abundance data collected from area-based bird surveys in grassland biofuel plots harvested via different pattern and percentage in western Minnesota, USA, from 2009 to 2013 (Chapter 1). Small mammal trapping was conducted in the same plots from 2009 to 2012, and abundance and occupancy data collected from these surveys was also analyzed (Chapter 2). I estimated relative abundance of 11 species of grassland birds and 7 species/genera of small mammals among the different harvest intensities and years of study. Four bird species and species richness showed declines in abundance following harvests, whereas two species showed increases in abundance. Harvests also resulted in negative impacts on two small mammals. The removal of vegetation in fall results in shorter, less dense vegetation the following spring, which creates largely unsuitable habitat for tall-grass songbirds (e.g., sedge wren) but more optimal habitat for species that prefer shorter vegetation (e.g., grasshopper sparrow). Additionally, the reduction in ground litter is detrimental to small mammals that prefer thicker vegetation (e.g., voles of the genus Microtus). At the community level, harvesting native grasslands appears to have little impact on grassland birds and small mammals, but it is nonetheless important to identify what species are present prior to harvesting so that harvesting activities do not result in detriment to these species.
  • Thumbnail Image
    Item
    Scale-dependent Response by Breeding Songbirds to Residential Development Along Lake Superior
    (2010) Ford, Michelle T; Flaspohler, David J
    This is the first study to examine the influence of Great Lakes shoreline residential development on forest breeding bird communities on any of the Great Lakes. This study took place near Houghton Michigan but may be relevant for Minnesota’s coastal areas given that migrating birds utilize common flyways, and their habitat and movements have trans-boundary characteristics. For these reasons it is included in the study. The abstract and key points are reproduced below. Abstract: “We examined the influence of shoreline residential development on breeding bird communities along forested portions of Lake Superior and hypothesized that anthropogenic changes related to housing development would alter bird community structure compared to areas without human development. We used point counts to compare relative abundance of bird species in relation to residential development at coarse (along 1 km shoreline stretches with and without housing/cottage development) and fine (developed and undeveloped sides of a shoreline access road) spatial scales during the 2005 breeding season. More species had development related differences in abundance at the finer-scale analysis than at the coarse scale. American Crows and American Robins were more abundant on the developed, shoreline side of shoreline access roads. Red-breasted Nuthatches, Blackthroated Green Warblers, and Red-eyed Vireos were more abundant on the undeveloped, inland side of shoreline access roads. Several species were detected exclusively in developed or undeveloped forest areas. The pattern of development-related differences in relative abundance of bird species depended on the scale at which data were analyzed, suggesting that many species may respond to habitat differences within the 100 m scale quite distinct from how they respond to differences at the scale of thousands of meters.”