Geology Reports⌕ Search

Geology topics

Leigh H. Fredrickson

Publications and source records attributed to Leigh H. Fredrickson.

5 recordsLinked to original sources
USGS2002

An application of queuing theory to waterfowl migration

There has always been great interest in the migration of waterfowl and other birds. We have applied queuing theory to modelling waterfowl migration, beginning with a prototype system for the Rocky Mountain Population of trumpeter swans (Cygnus buccinator) in Western North America. The queuing model can be classified as a D/BB/28 system, and we describe the input sources, service mechanism, and network configuration of queues and servers. The intrinsic nature of queuing theory is to represent the spatial and temporal characteristics of entities and how they move, are placed in queues, and are serviced. The service mechanism in our system is an algorithm representing how swans move through the flyway based on seasonal life cycle events. The system uses an observed number of swans at each of 27 areas for a breeding season as input and simulates their distribution through four seasonal steps. The result is a simulated distribution of birds for the subsequent year's breeding season. The model was built as a multiagent system with one agent handling movement algorithms, with one facilitating user interface, and with one to seven agents representing specific geographic areas for which swan management interventions can be implemented. The many parallels in queuing model servers and service mechanisms with waterfowl management areas and annual life cycle events made the transfer of the theory to practical application straightforward.

Rocky Mountains↗
USGS1994

Late winter survival of female mallards in Arkansas

Determining factors that limit winter survival of waterfowl is necessary to develop effective management plans. We radiomarked immature and adult female mallards ( Anas platyrhynchos ) after the 1988 and 1989 hunting seasons in eastcentral Arkansas to test whether natural mortality sources and habitat conditions during late winter limit seasonal survival. We used data from 92 females to calculate survival estimates. We observed no mortalities during 2,510 exposure days, despite differences in habitat conditions between years. We used the binomial distribution to calculate daily and 30-day survival estimates plus 95% confidence intervals of 0.9988 ≤ 0.9997 ≤ 1.00 and 0.9648 ≤ 0.9925 ≤ 1.00, respectively. Our data indirectly support the hypothesis that hunting mortality and habitat conditions during the hunting season are the major determinants of winter survival for female mallards in Arkansas.

Arkansas↗
USGS1991

Chufa biology and management

Chufa (Cyperus esculentus) is an emergent perennial sedge that is common in seasonally flooded wetlands. Although chufa is common in many States, it is most abundant in the Southeast, including the Mississippi alluvial valley (Fig. 1). Belowground biomass of chufa, especially the tubers, serves as a valuable food source for waterfowl and cranes. Chufa tubers rank tenth among the most important waterfowl foods in the United States.

Fish and Wildlife Leaflet↗