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- Title
- LANDCOVER CHANGE AND POPULATION DYNAMICS OF FLORIDA SCRUB-JAYS AND FLORIDA GRASSHOPPER SPARROWS.
- Creator
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Breininger, David, Noss, Reed, University of Central Florida
- Abstract / Description
-
I confronted empirical habitat data (1994-2004) and population data (1988-2005) with ecological theory on habitat dynamics, recruitment, survival, and dispersal to develop predictive relationships between landcover variation and population dynamics. I focus on Florida Scrub-Jays, although one chapter presents a model for the potential influence of habitat restoration on viability of the Florida Grasshopper Sparrow. Both species are unique to Florida landscapes that are dominated by shrubs and...
Show moreI confronted empirical habitat data (1994-2004) and population data (1988-2005) with ecological theory on habitat dynamics, recruitment, survival, and dispersal to develop predictive relationships between landcover variation and population dynamics. I focus on Florida Scrub-Jays, although one chapter presents a model for the potential influence of habitat restoration on viability of the Florida Grasshopper Sparrow. Both species are unique to Florida landscapes that are dominated by shrubs and grasses and maintained by frequent fires. Both species are declining, even in protected areas, despite their protected status. I mapped habitat for both species using grid polygon cells to quantify population potential and habitat quality. A grid cell was the average territory size and the landcover unit in which habitat-specific recruitment and survival occurred. I measured habitat-specific recruitment and survival of Florida Scrub-Jays from 1988-2008. Data analyses included multistate analysis, which was developed for capture-recapture data but is useful for analyzing many ecological processes, such as habitat change. I relied on publications by other investigators for empirical Florida Grasshopper Sparrow data. The amount of potential habitat was greatly underestimated by landcover mapping not specific to Florida Scrub-Jays. Overlaying east central Florida with grid polygons was an efficient method to map potential habitat and monitor habitat quality directly related to recruitment, survival, and management needs. Most habitats for both species were degraded by anthropogenic reductions in fire frequency. Degradation occurred across large areas. Florida Scrub-Jay recruitment and survival were most influenced by shrub height states. Multistate modeling of shrub heights showed that state transitions were influenced by vegetation composition, edges, and habitat management. Measured population declines of 4% per year corroborated habitat-specific modeling predictions. Habitat quality improved over the study period but not enough to recover precariously small populations. The degree of landcover fragmentation influenced mean Florida Scrub-Jay dispersal distances but not the number of occupied territories between natal and breeding territories. There was little exchange between populations, which were usually further apart than mean dispersal distances. Florida Scrub-Jays bred or delayed breeding depending on age, sex, and breeding opportunities. I show an urgent need also for Florida Grasshopper Sparrow habitat restoration given that the endangered bird has declined to only two sizeable populations and there is a high likelihood for continued large decline. A major effect of habitat fragmentation identified in this dissertation that should apply to many organisms in disturbance prone systems is that fragmentation disrupts natural processes, reducing habitat quality across large areas. Humans have managed wildland fire for > 40,000 years, so it should be possible to manage habitat for many endangered species that make Florida's biodiversity unique. This dissertation provides methods to quantify landscape units into potential source and sink territories and provides a basis for applying adaptive management to reach population and conservation goals.
Show less - Date Issued
- 2009
- Identifier
- CFE0002537, ucf:47638
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0002537
- Title
- Estimated diets, diet overlap, and winter habitat associations of four grassland sparrows in Florida dry prairie.
- Creator
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Korosy, Marianne, Noss, Reed, Quintana-Ascencio, Pedro, Roth, James, Hinkle, Ross, Bowman, Reed, University of Central Florida
- Abstract / Description
-
North American grassland birds show long-term population declines that generally exceed the declines of other bird groups. Efforts to conserve grassland birds require knowledge of diet and habitat requirements during both the breeding and nonbreeding periods of annual life cycles. This dissertation investigated sparrow habitat associations within two defined plant communities of the dry prairie ecosystem, the dry-mesic and wet-mesic prairie, for four prescribed fire treatments over two...
Show moreNorth American grassland birds show long-term population declines that generally exceed the declines of other bird groups. Efforts to conserve grassland birds require knowledge of diet and habitat requirements during both the breeding and nonbreeding periods of annual life cycles. This dissertation investigated sparrow habitat associations within two defined plant communities of the dry prairie ecosystem, the dry-mesic and wet-mesic prairie, for four prescribed fire treatments over two consecutive winters. Grasshopper and Henslow's sparrows showed higher relative abundance in wet-mesic prairie and Bachman's Sparrows were more abundant in dry-mesic prairie across all fire treatments. Abundances of Grasshopper and Bachman's sparrows were best predicted by plant community association and secondly by time since fire; whereas for Henslow's Sparrows, habitat and time since fire were equally important. Fall molt-period diets and diet overlap were modeled for resident Florida Grasshopper and Bachman's sparrows using stable carbon and nitrogen isotope ratios of bird feathers and potential food sources, e.g., arthropods and seeds. Grasshoppers (Orthoptera, including a variety of species foraging on both C3 and C4 herbs), spiders, dragonflies, flies, beetles and weevils comprised the majority of the diets of adult and juvenile Florida Grasshopper Sparrows and Bachman's Sparrows, but in differing proportions. Despite the similarity in reconstructed diets for the two sparrow species, analysis of diet overlap suggested that approximately half of the Florida Grasshopper Sparrows had diets consisting of higher trophic level prey than Bachman's Sparrows. Winter diets and diet overlap among Grasshopper, Henslow's, and Bachman's sparrows were reconstructed using stable carbon and nitrogen isotope ratios of feathers and potential arthropod and seed food sources. Sparrows were captured and recaptured in winter 2007-2008 using systematic flush-netting, removing a tail feather at first capture and then removing the regrown feather when birds were recaptured. Winter diets of all three sparrows included a variety of arthropods, grass seeds, and sedge seeds, but Bachman's Sparrow winter diets spanned greater trophic diversity than either of the migratory sparrows. Estimated diets of Henslow's and Grasshopper sparrows differed from that of Bachman's Sparrow but Henslow's Sparrow diets did not differ from Grasshopper Sparrow diets. This is the first study of fall and winter sparrow diets in Florida based on stable isotopes and the first study in peninsular Florida on habitat associations of ground-dwelling sparrows.
Show less - Date Issued
- 2013
- Identifier
- CFE0005363, ucf:50475
- Format
- Document (PDF)
- PURL
- http://purl.flvc.org/ucf/fd/CFE0005363
