Salmon increase forest bird abundance and diversity.

Area of Science:

• Ecology
• Wildlife Biology
• Conservation Science

Background:

• Marine-derived nutrients from Pacific salmon (Oncorhynchus spp.) can significantly impact terrestrial ecosystems.
• Salmon subsidies influence forest fertilization, invertebrate abundance, and potentially affect breeding bird populations.

Purpose of the Study:

• To quantify the influence of varying Pacific salmon biomass on songbird community abundance and composition.
• To identify key drivers of terrestrial bird communities in salmon-spawning stream ecosystems.

Main Methods:

• Conducted point-count surveys for birds over two years across 14 streams in British Columbia, Canada.
• Collected data on salmon spawning biomass and 13 environmental covariates in riparian forests.
• Utilized statistical analyses to correlate bird community metrics with salmon biomass and environmental factors.

Main Results:

• Songbird abundance and avian diversity were positively correlated with increased salmon biomass.
• Watershed size and forest composition were found to be less significant predictors of bird communities compared to salmon biomass.
• Specific foraging guilds and individual species showed varying responses to salmon subsidies.

Conclusions:

• Pacific salmon play a crucial role in supporting terrestrial songbird communities, acting as a significant resource subsidy.
• Findings highlight the importance of salmon for forest ecosystem health and terrestrial biodiversity.
• This research provides valuable data for informing ecosystem-based management strategies that consider the terrestrial impacts of salmon populations.