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Wilson’s Warbler

Wilson’s Warbler
Forest condition: Mature/Young Forest
Habitat Attribute: Deciduous Understory

Habitat Objectives
Landscapes: Within landscapes >1,000 ha (2,500 ac) maintain a complex heterogeneity of habitat types and conditions including
– >60% of the area in contiguous deciduous or mixed deciduous-coniferous forest
– >4% of the area in early successional habitat in corridor-type strips or complex shapes (i.e., not uniform in shape) to maximize edge.
Sites: Where ecologically appropriate in forests >40 years old provide
– >40% understory cover of deciduous shrubs and small trees (<10ft)
– >25% of the shrub cover as western sword fern or bracken fern
Sites: Riparian buffer zones within harvest units should be >30 m (100 ft) wide to provide suitable habitat, and should meet site-level habitat conditions described above

Habitat Conservation Strategies
– In forests managed for wood products, extend rotation age to >60 years in conjunction with thinning as described below to lengthen suitability of the habitat for a longer period of time.
– If understory deciduous vegetation has not been maintained through earlier successional stages, conduct moderate to heavy variable-density thinning to create canopy openings and small gaps (<1 ha [2 ac]) to promote understory shrub development.
– Small patch (0.2 ha [0.5 ac]) group selection cuts, rather than green-tree retention or modified clearcuts, may provide habitat since these cuts have the overall least impact on important habitat features in the unharvested understory (Chambers 1996).
– If patches of understory deciduous vegetation have been maintained through earlier successional stages, conduct thinning as necessary to prevent conifers from competing and shading out deciduous understory.
– Because the time frame of understory response to commercial thinning is <10 years (Alaback and Herman 1988), repeated thinnings may be necessary to advance understory development.
– During thinning, activities should be carefully designed and logging systems tailored to site-specific conditions to minimize understory disturbance and site productivity (e.g., road systems and skid trails, type of harvest and equipment), especially tall shrub cover (Hagar 2004).
– In harvest units, retain intact patches of forest with understories rather than dispersed trees or aggregate clumps of trees with treated understories.
-Discontinue use of herbicides for deciduous tree and shrub control for species associated with a deciduous understory

Altman, B. and J.D. Alexander. 2012. Habitat conservation for landbirds in coniferous forests of western Oregon and Washington. Version 2.0. Oregon-Washington Partners in Flight ( and American Bird Conservancy and Klamath Bird Observatory.