Presentation Abstract
The semelparous salmonid species are the ecological foundation of Pacific Northwest coastal ecosystems, which span across the international border to encompass the Salish Sea. The annual return of salmonids to their natal streams and decomposition of their carcasses deposits marine-derived nutrients into freshwater ecosystems, which are integral to food web dynamics, nutrient cycling and habitat quality. Bald eagles (Haliaeetus leucocephalus) are apex predators that congregate along riverbanks to scavenge accumulated carcasses, which results in individuals using piracy to steal food items from others. Winners fly to nearby trees to consume carcasses, which are dropped to the forest floor and decomposed by terrestrial invertebrates. While this transfer of nutrients is critical to terrestrial habitat quality, the current decline in salmon populations in the Salish Sea could alter this cycle. Thus, the aim of our study is to determine if a decrease in carcass abundance will alter the piracy rates among eagles and the amount of marine-derived nutrients that are transferred into forests. To accomplish this, field observations on piracy rates will be compared to a simulated crash in salmon populations in an Individual-Based Model to determine how eagles alter their behaviour under decreased carcass abundance. The results will be compared to an isotope analysis of terrestrial invertebrates from perch tree locations. Predicted results include: a) the piracy rate in the IBM will be higher when fewer carcasses are available, b) less nutrients will be transferred to terrestrial ecosystems under low carcass abundance and high competition and c) the N and C isotopic signatures in terrestrial invertebrates under perch trees will be higher than controls. The results of this study will be used in collaboration with other fields to take an ecosystem-based approach to ensure coastal food web dynamics, nutrient cycling and habitat quality are priorities in our transboundary salmon management strategies.
Session Title
Transboundary Monitoring of Marine Birds and Mammals in the Salish Sea
Keywords
Bald eagles, Nutrient cycling
Conference Track
SSE7: Monitoring: Species and Habitats
Conference Name
Salish Sea Ecosystem Conference (2018 : Seattle, Wash.)
Document Type
Event
SSEC Identifier
SSE7-460
Start Date
4-4-2018 2:15 PM
End Date
4-4-2018 2:30 PM
Type of Presentation
Oral
Genre/Form
presentations (communicative events)
Contributing Repository
Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.
Subjects – Topical (LCSH)
Salmonidae--Predators of--Ecology--Salish Sea (B.C. and Wash.); Eagles--Behavior--Salish Sea (B.C. and Wash.); Top predators--Salish Sea (B.C. and Wash.); Habitat (Ecology)--Salish Sea (B.C. and Wash.)
Geographic Coverage
Salish Sea (B.C. and Wash.)
Rights
This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.
Type
Text
Language
English
Format
application/pdf
Included in
Fresh Water Studies Commons, Marine Biology Commons, Natural Resources and Conservation Commons, Terrestrial and Aquatic Ecology Commons
Apex predator behaviour in a changing Salish Sea: determining the role bald eagle foraging behaviour plays in nutrient cycling and terrestrial food webs under diminishing salmon populations
The semelparous salmonid species are the ecological foundation of Pacific Northwest coastal ecosystems, which span across the international border to encompass the Salish Sea. The annual return of salmonids to their natal streams and decomposition of their carcasses deposits marine-derived nutrients into freshwater ecosystems, which are integral to food web dynamics, nutrient cycling and habitat quality. Bald eagles (Haliaeetus leucocephalus) are apex predators that congregate along riverbanks to scavenge accumulated carcasses, which results in individuals using piracy to steal food items from others. Winners fly to nearby trees to consume carcasses, which are dropped to the forest floor and decomposed by terrestrial invertebrates. While this transfer of nutrients is critical to terrestrial habitat quality, the current decline in salmon populations in the Salish Sea could alter this cycle. Thus, the aim of our study is to determine if a decrease in carcass abundance will alter the piracy rates among eagles and the amount of marine-derived nutrients that are transferred into forests. To accomplish this, field observations on piracy rates will be compared to a simulated crash in salmon populations in an Individual-Based Model to determine how eagles alter their behaviour under decreased carcass abundance. The results will be compared to an isotope analysis of terrestrial invertebrates from perch tree locations. Predicted results include: a) the piracy rate in the IBM will be higher when fewer carcasses are available, b) less nutrients will be transferred to terrestrial ecosystems under low carcass abundance and high competition and c) the N and C isotopic signatures in terrestrial invertebrates under perch trees will be higher than controls. The results of this study will be used in collaboration with other fields to take an ecosystem-based approach to ensure coastal food web dynamics, nutrient cycling and habitat quality are priorities in our transboundary salmon management strategies.
