Incorporating Key Restoration Decisions into Habitat Suitability Models to Forecast Outcomes for Southwestern Willow Flycatchers (SWFL)
Lisa M. Markovchick1*, James L. Tracy2
1Department of Biological Sciences, Northern Arizona University, Flagstaff, AZ 86011, U.S.A. Lisa_Markovchick@nau.edu
2Department of Entomology, Texas A&M University, College Station, TX, 77843, U.S.A. jamesltracy@tamu.edu
Carefully designed restoration projects for the federally endangered southwestern willow flycatcher (Empidonax traillii extimus) may mitigate impacts to exotic tamarisk (Tamarix spp.) nesting areas defoliated by expanding populations of introduced tamarisk beetles (Diorhabda spp.). We demonstrate the use of restoration scenarios coupled with a flycatcher nesting habitat suitability index (HSI) model to assist with detailed restoration site planning for flycatchers. Native nesting habitats of flycatchers are typified by extensive canopy cover of willows (Salix spp.) and cottonwoods (Populus spp.) critical to nest thermoregulation and success. Survival and growth of these native trees are benefitted by the addition of mycorrhizal fungi, particularly in areas invaded by tamarisk. Two key restoration considerations were incorporated into flycatcher HSI model scenarios and simulations: 1) selection of the percentage of willow and cottonwood composition and spacing, and 2) whether or not to inoculate the soil with mycorrhizal fungi. Restoration scenarios were simulated at a Tonto Creek, Arizona flycatcher nesting area over a three year period following planting to assess their influence on the quality of flycatcher nesting habitat suitability. Implementing willow/cottonwood restoration scenarios into a flycatcher HSI model provides a critical tool for land managers to evaluate restoration options and their outcomes in site-specific flycatcher nest habitat restoration planning.