“Does management for enhancing recreational values in suburban

woodlands affect the intensity of bird predation on canopy-living arthropods?”

Khanh Duong,Mark Griffith,Alicia McCusker

UNST 181 A 4/20/2011

Erik Heyman & Bengt Gunnarsson

History Previous studies show Insectivorous birds aid in controlling the population of the arthropods on which they prey

Many suburban forests are clearing understory for aesthetic and recreation value

Increase in leaf damage

Ultimately question asked and studied in two Swedish forests

Methods2 similar sites were chosen

The Hultaberg site (area 8.0 ha)The Rya åsar site (7.2 ha)

Understory clearance was conducted at both sites4.0 ha at Hultaberg site3.9 ha at Rya åsar site

Methods: Experimental Procedure44 Oak trees were randomly selected.

24 trees were located at the Hultaberg site20 trees were located at the Rya åsar site

4 branches were randomly selected for each tree2 low branches (3-5 m above ground)2 high branches (12-15 m above ground)

Each height had one plastic anti-bird net

Experimental setup. The experiment was replicated at two sites. Each site was divided in two plots of equal area which were randomly assigned to either understory clearance or no management (control). Bird enclosures were placed in 10-12 trees in each plot, at two height levels in each tree.

Methods: CollectionNet-enclosed and control branches were cut

and stored in bagsArthropods were collected and preservedAll leaves were removed from branches and

weighedControl for differences in branch size

ResultsArthropod biomass of the

six largest orders in relation to experimental treatment and management

dotted line - dense understory

full line - understory clearance

Results Cont.

ConclusionInsectivorous birds significantly decrease

arthropod populations in forest and agricultural ecosystems.

Population control of arthropods is higher in the areas with dense understory.Human activity in less dense understory

could have disrupted the birds.Negative effects on recreation because

arthropod increase tree leaf damage.

Extended and future research suggestion: The effect of human presence on the birds feeding

Times that they feed

Where nest are built in correlation to foot trails

Density of arthropods around foot trails and human activity

Better ExplanationArthropod- invertebrate

with exoskeleton, segmented body and appendages.How many?

Wood understory- group of small trees, shrubs and vines that grow under the taller trees.

Didn't give any other reasons why the birds left.

Example of arthropods

Relevance to Sustainability• Reduces pest population of ecosystem.• Allows agriculture and forestry to flourish.• Without birds increase leaf damage has been

found.