Joan Hagar, USGS-FRESC Judy Li and Janel Sobota, OSU Department of Fish & Wildlife Designed to protect AQUATIC resources Riparian habitat is also important for some TERRESTRIAL wildlife species Function of headwater riparian areas as habitat for terrestrial species? Higher abundance and diversity of birds reputed for riparian habitat Emergent aquatic insects may provide a “subsidy” to terrestrial consumers Higher capture rates of some bird species in Trask headwater riparian areas compared to uplands Do aquatic subsidies explain riparian association? Deciduous vegetation supports more arthropod prey than conifers Deciduous tends to flourish streamside, Conifers upslope Pattern less pronounced on high-gradient headwater streams Changes in distribution of arthropod prey in relation to stream size? Relate the distribution of birds along inter- riparian gradients in headwater forests to availability of insect prey • What are riparian- associated birds eating? — Aquatic vs terrestrial arthropods • Does prey availability (Terrestrial and Aquatic) differ between Riparian and Upland habitats? 6 Sites: 2008 2009 GS1 GS1 PH3 PH3 PH2 GS3 PH4 UM3 Swainson’s Thrush, Pacific-slope Flycatcher, Wilson’s Warbler, and Pacific Wren Diet samples collected from birds captured in nets ID fragments in fecal samples to Order; Aquatic vs Terrestrial Stream Streamside and Upland Emergence: Adult Aquatic Malaise: Adult Aquatic Insects and Terrestrial Insects (2x per week) (once per week) What are the birds eating? 1.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 Pac-Slope Flycatcher 0.2 Wilson's Warbler 0.1 0.0 0.9 0.8 0.7 0.6 0.5 0.4 0.3 Swainson's Thrush 0.2 Pacific Wren 0.1 0.0 Beetles and Flies were popular fare Aquatic emergents (EPT) rare Fruit was important in Swainson’s thrush diet Gradients in arthropod prey availability 100 90 80 70 60 50 40 Riparian 30 20 Upland 10 0 *Others: Neuroptera, Psocoptera Biomass of Flying Insects (>2 mm) 1.2 RIPARIAN UPLAND 1.0 0.8 0.6 0.4 (Mean + S.E.) 0.2 Dry Mass (g)/Week 0.0 2008 2009 Flying Insects (>2 mm <25 mm) in Summer 250 2008 RIPARIAN 200 UPLAND 150 100 50 0 6/26 7/16 8/5 8/25 Flying Insects (>2 mm <25 mm) in Summer 250 2008 RIPARIAN 200 UPLAND 150 100 50 0 6/26 7/6 7/16 7/26 8/5 8/15 8/25 (Mean + S.E.) Individuals/day 250 2009 200 150 100 50 0 6/26 7/6 7/16 7/26 8/5 8/15 8/25 Little evidence of aquatic emergent insects in bird diets Aquatic insects represented small proportion of available prey biomass Terrestrial food resources most important to birds More prey in riparian than upslope samples Distinct riparian vegetation may influence prey abundance Riparian vegetation contributes to aquatic and terrestrial food webs Understory may be helpful in defining management zones .