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Headwater Riparian Habitat: Prime Real Estate For Birds. Joan Hagar, USGS-FRESC Judy Li and Janel Sobota , OSU Department of Fish & Wildlife. Riparian Reserves. Designed to protect AQUATIC resources Riparian habitat is also important for some TERRESTRIAL wildlife species

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Headwater riparian habitat prime real estate for birds

Headwater Riparian Habitat: Prime Real Estate For Birds

Joan Hagar, USGS-FRESC

Judy Li and JanelSobota, OSU Department of Fish & Wildlife


Riparian reserves
Riparian Reserves

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?


Riparian upland gradients birds and insects
Riparian-Upland Gradients: Birds and Insects

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?


Riparian upland gradients vegetation
Riparian-Upland Gradients: Vegetation

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?


Research goal
Research Goal

Relate the distribution of birds along inter-riparian gradients in headwater forests to availability of insect prey


Research questions
Research Questions

  • What are riparian-associated birds eating?

    • Aquatic vs terrestrial arthropods

  • Does prey availability (Terrestrial and Aquatic) differ between Riparian and Upland habitats?


Trask river study sites
Trask River Study Sites

6 Sites:


Methods what are riparian associated birds eating
Methods: What are riparian-associated birds eating?

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


Methods assessing prey availability for birds
Methods: Assessing Prey Availability for Birds

Streamside and Upland

Malaise: Adult Aquatic and Terrestrial Insects

(once per week)

Stream

Emergence: Adult Aquatic Insects

(2x per week)


Results

RESULTS:

What are the birds eating?



Diets of swainson s thrush n 73 and pacific wren n 23
Diets of Swainson’s Thrush (n=73) and Pacific Wren (n=23)


Bird diet highlights
Bird Diet Highlights

Beetles and Flies were popular fare

Aquatic emergents (EPT) rare

Fruit was important in Swainson’s thrush diet


Results1

RESULTS:

Gradients in arthropod prey availability


Malaise trap results flying insects 2 mm 25 mm
Malaise trap Results:Flying Insects >2 mm <25 mm

*Others:Neuroptera, Psocoptera



Headwater riparian habitat prime real estate for birds

2008


Headwater riparian habitat prime real estate for birds

2008

Individuals/day

(Mean + S.E.)



No evidence of aquatic subsidy
No Evidence of Aquatic Subsidy

  • 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


Prey abundance varied from streamside to upland
Prey abundance varied from streamside to upland

More prey in riparian than upslope samples

Distinct riparian vegetation may influence prey abundance


Conclusions1
Conclusions

Riparian vegetation contributes to aquatic and terrestrial food webs

Understory may be helpful in defining management zones