“Does the management for enhancing recreational values in

suburban woodlands affect the intensity of bird predation on

canopy-living arthropods”

Article by: Erik Heyman & Bengt Gunnarsson

Presented by: Khanh Duong, Mark Griffith & Alicia McCusker

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

Methods

2 similar sites were chosen The Hultaberg site (area 8.0 ha) The Rya åsar site (7.2 ha)

Understory clearance was conducted at both sites 4.0 ha at Hultaberg site 3.9 ha at Rya åsar site

Methods: Experimental Procedure

44 Oak trees were randomly selected. 24 trees were located at the Hultaberg site 20 trees were located at the Rya åsar site

4 branches were randomly selected for each tree 2 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: Collection

Net-enclosed and control branches were cut and stored in bags

Arthropods were collected and preserved All leaves were removed from branches and

weighed Control for differences in branch size

Results

Arthropod biomass of the six largest orders in relation to experimental treatment and management

dotted line - dense understory full line - understory clearance

Results contd.

Conclusion

Insectivorous 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 Explanation Arthropod- 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.