Long-term population trends of colonial wading birds (Ciconiiformes) in Louisiana, Florida, Texas, and California were examined using data from Audubon Christmas Bird Counts (1949-1988) and Breeding Bird Surveys (1966-1989). Winter populations of most Louisiana wading birds increased over the 40-year period, with the sharpest increases occurring during the last 20 years. Increased acreage of crayfish (Procambarus) aquaculture in Louisiana appears to be the most significant factor explaining the observed population increases. First, populations of wading-bird species that use crayfish were correlated positively with the wild crayfish harvest, and more strongly with crayfish pond acreage. Second, the regularity of pond management provided a more predictable foraging habitat than did comparable natural areas. Third, the use of crayfish ponds by wading birds peaked during pond drawdowns, which may have increased reproductive success by concentrating prey available to wading birds during their nesting season. Fourth, wading bird species that specialized on crayfish showed the greatest population increases and the strongest correlation with crayfish pond acreage A field study comparing crayfish farms with natural habitats found significant differences in prey availability, and in the relative foraging success of Great Egrets, Snowy Egrets, and White Ibises. Wading birds on crayfish farms took significantly more prey for less effort, and selected more preferred prey. Wild sites had more fish $(P<0.001),$ more total prey $(P<0.001),$ and higher prey densities $(P<0.001)$ than flooded farm ponds. Farm ponds during drawdown, however, had higher densities of fish, more crayfish $(P<0.001),$ and higher prey densities than wild sites $(P<0.001).$ When foraging on crayfish farms, Great Egrets took more total prey $(P<0.05),$ Snowy Egrets took more fish $(P<0.05),$ and White Ibises took more crayfish $(P<0.01)$ than in the wild. Juvenile White Ibis foraged significantly more successfully on crayfish farms than did adult birds on farms or in the wild. Crayfish farms thus provide superior foraging habitats for wading birds during the nesting season. Recent increases in crayfish farm acreage in Louisiana appear to be a major factor causing the long-term population increases of Louisiana's colonial wading birds. These findings have important implications for the conservation and management of Louisiana's wading bird populations / acase@tulane.edu
| Identifer | oai:union.ndltd.org:TULANE/oai:http://digitallibrary.tulane.edu/:tulane_23296 |
| Date | January 1996 |
| Contributors | Fleury, Bruce Edward (Author), Sherry, Thomas W (Thesis advisor) |
| Publisher | Tulane University |
| Source Sets | Tulane University |
| Language | English |
| Detected Language | English |
| Rights | Access requires a license to the Dissertations and Theses (ProQuest) database., Copyright is in accordance with U.S. Copyright law |
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