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 (Seattle, WA : 2018)

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

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

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

Share

COinS
 
Apr 4th, 2:15 PM Apr 4th, 2:30 PM

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.