The Henslows Sparrow (Ammodramus henslowii) is a grassland species of concern that winters in prairies and open pine savannas across the Gulf Coastal Plain. Previous studies have indicated that these birds occur at higher densities in recently burned habitats in winter, but this has never been examined over a large geographic area containing multiple habitat types. The objectives of the study were to identify areas of important winter habitat in Louisiana, to examine the relationship between time since burn, bird density, and bird condition, and to determine vegetation structure and composition used by birds. We found most of the new potential habitat and the highest numbers of birds in two specific ecoregions, the Lower West Gulf Coastal Plain and the East Gulf Coastal Plain (east and west) suggesting that these may be most important for wintering Henslows Sparrows. Time since burn explained little variation plot selection overall. Bird densities in the east peaked in the first winter after burn, while densities in the west were higher 1-2 years post burn, indicating that habitats in these regions may respond differently to fire. Vegetation measurements were not helpful in interpreting bird abundance patterns across plots, suggesting that characteristics of suitable habitat may vary widely across ecoregions. However, within a plot the probability of flushing a bird increased with increasing herbaceous density at ground level, and with increasing cover of the plant genera Andropogon and Rhynchospora, so Henslows Sparrows may be responding to structural components of the habitat on a small scale. Sex ratios and bird body condition, including mass, fat storage, and feather growth, did not vary with burn year. Therefore I found no evidence for any sex-related winter hierarchy. Results of this research will help land managers make decisions with appropriate consideration for the larger variation in bird abundance and vegetation associations found across a regional scale. We recommend a two year rotation of prescribed fire to maintain high numbers of Henslows Sparrows, and caution against more frequent fire rotations in the west.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04082008-145552 |
| Date | 16 April 2008 |
| Creators | Palasz, Laura M. |
| Contributors | Kyle E. Harms, Michael Chamberlain, Philip C Stouffer |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04082008-145552/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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