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Geology topics

J. L. Curnutt

Publications and source records attributed to J. L. Curnutt.

5 recordsLinked to original sources
USGS2006

Population dynamics of the endangered Cape Sable seaside-sparrow

The Cape Sable seaside-sparrow ( Ammodramus maritimus mirabilis ) has disappeared from its only known breeding areas episodically since its discovery early this century. Systematic surveys across its range in the southern Everglades find the sparrow's range to be fragmented into six subpopulations. The sparrow population decreased by 58% between 1992 and 1995, with the near extinction of the western half of the population and the temporary local extinction of some eastern populations. Other similar grassland sparrows have populations that vary considerably from year to year. Yet the decline in the western subpopulation and the local extinction of some of the peripheral populations cannot be explained by natural variability alone. Hurricane Andrew passed over several subpopulations prior to the particularly poor year of 1993. However, the geographical and temporal patterns of subpopulation decline are not consistent with what would be expected following a hurricane. Frequent fires prevent successful breeding as does flooding during the breeding season. Better management can prevent frequent fires and episodic flooding. However, the long-term survival of the sparrow depends on managing the unanticipated risks that attend its small, fragmented population.

Animal Conservation↗
USGS2006

Water levels, rapid vegetational changes, and the endangered Cape Sable seaside-sparrow

The legally endangered Cape Sable seaside-sparrow ( Ammodramus maritimus mirabilis ) is restricted to short-hydroperiod, marl prairies within Florida's Everglades National Park and Big Cypress National Preserve. Marl prairies are typified by dense, mixed stands of graminoid species usually below 1 m in height, naturally inundated by freshwater for 3–7 months annually. Water levels affect the birds directly, by flooding their nests, and indirectly by altering the habitat on which they depend. Managed redistribution of water flows flooded nearly half of the sparrow's geographical range during several consecutive breeding seasons starting in 1993. Furthermore, these high water levels rapidly changed plant communities, so jeopardizing the sparrow's survival by reducing the availability of nesting habitat.

Florida↗
USGS2000

Landscape-based spatially explicit species index models for everglades restoration

As part of the effort to restore the ∼10 000-km 2 Everglades drainage in southern Florida, USA, we developed spatially explicit species index (SESI) models of a number of species and species groups. In this paper we describe the methodology and results of three such models: those for the Cape Sable Seaside Sparrow and the Snail Kite, and the species group model of long-legged wading birds. SESI models are designed to produce relative comparisons of one management alternative to a base scenario or to another alternative. The model outputs do not provide an exact quantitative prediction of future biotic group responses, but rather, when applying the same input data and different hydrologic plans, the models provide the best available means to compare the relative response of the biotic groups. We compared four alternative hydrologic management scenarios to a base scenario (i.e., predicted conditions assuming that current water management practices continue). We ranked the results of the comparisons for each set of models. No one scenario was beneficial to all species; however, they provide a uniform assessment, based on the best available observational information, of relative species responses to alternative water-management plans. As such, these models were used extensively in the restoration planning.

Florida↗
USGS1994

Bald eagle nest site characteristics in South Florida

Florida had nearly 20% of the coterminous United States population of nesting bald eagles ( Haliaeetus leucocephalus ) in 1990 (U.S. Fish and Wildl. Serv. 1991), yet the nesting ecology of bald eagles in subtropical environments has not been investigated. We examined nest site selection (n = 156 sites) by bald eagles in Florida Bay, Florida, from 1959 to 1990. Black ( Avicennia germinans ) and red mangroves ( Rhizophora mangle ) were used as nest trees almost exclusively (96.9%), and more than half were snags. Eagles also built nests on the ground (n = 3) and raised young on the ground after nests collapsed (n = 5). Eagles preferred (P < 0.05) higher keys (grass, hardwood-buttonwood [ Conocarpus erecta ]) over low-lying keys (mangrove, marsh) for nesting. Management strategies should include the preservation of live and dead mangroves and large, undisturbed keys as potential nesting sites for bald eagles in the subtropical portion of the eagle's range.

Florida↗