Simulating the effects of predation and egg-harvest at a gull colony. Final Report for Glacier Bay National Park, National Park Service
Zador S and Piatt JF. 2002. Simulating the effects of predation and egg-harvest at a gull colony. Final Report for Glacier Bay National Park, National Park Service. U.S. Geological Survey Alaska Science Center. Anchorage, AK
We developed an individual-based simulation model to explore the effects of harvesting eggs from a glaucous-winged gull (Larus glaucescens) colony that also experiences egg loss from avian predators. The model has direct application to Glacier Bay National Park, where resource managers are concerned about potential negative effects of traditional Native Alaskan harvesting of gull eggs at colonies within the park. The model simulates the sequence of egg laying, relaying, and incubation to hatching for individual nests and calculates hatching success, incubation length, total egg harvest, and total eggs laid in all nests during the simulation. Stochasticity is incorporated in the distribution of nest lay dates and in the number of nests attacked during predation and harvest events. Model outputs suggest that (1) harvest strategies are largely ineffectual when background predation rates are high, and, (2) harvesting early, at one time, and from no more than 20% of the colony provides a constant harvest with the least impact to gulls when background predation rates are low to moderate (and within the natural range observed in the field). Key words: egg-harvest, Glacier Bay, glaucous-winged gull, Larus glaucescens, predation, simulation
- Type
- Unpublished Report
- Authors
- Zador, SG; Piatt, J
- Date of Issue
- 2002
- Publisher
- U.S. Geological Survey Alaska Science Center
- Units
- GLBA
- Keywords
- Birds/Ornithology, breeding colony, Coastal/Marine Systems, egg harvesting, Glacier Bay, gull, Predation, Seabirds