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For planning and management purposes, agencies require a web application that can locate, map, and monitor Southwestern Willow Flycatcher (flycatcher) breeding habitat across its range. The Habitat Viewer can identify potential flycatcher habitat and monitor changes caused by stressors, such as beetles, fire or drought.
The Southwestern Willow Flycatcher (Empidonax traillii extimus, hereinafter referred to as “flycatcher”) is a federally endangered species that occurs along rivers and streams in the Southwestern United States during May–September (U.S. Fish and Wildlife Service, 1995, 2002). Flycatcher breeding habitat is characterized by a mosaic of relatively dense tree and shrub growth, typically in association with surface water or saturated soil, interspersed with more open areas, open water, or shorter, sparser vegetation along rivers, streams, or other wetlands. Habitat loss and degradation are the main factors contributing to the decline of the species and the flycatcher recovery plan emphasizes the increase and improvement of breeding habitat through restoration of native breeding habitat and the management of exotic vegetation (U.S. Fish and Wildlife Service, 2002). The estimated rangewide breeding population of flycatchers as of the last compilation in 2007 was roughly 1,299 territories distributed among 288 known sites (Durst and others, 2008). In 2013, the U.S. Fish and Wildlife Service (FWS) designated revised critical habitat for the flycatcher under the Endangered Species Act (U.S. Fish and Wildlife Service, 2013). Hundreds of stream kilometers were designated as critical habitat, located in 6 states, 38 counties, 24 management units, and 6 recovery units. Identified by stream segment, the lateral extent includes riparian areas and streams in the 100-year floodplain (Fig. 1).
The Arizona Game and Fish Department developed a flycatcher remote sensing/geographic information system (GIS) habitat model (hereinafter referred to as the “satellite model”) that uses Landsat imagery and a 30-m-resolution digital elevation model (Hatten and Paradzick, 2003). The satellite model was developed with presence/absence survey data acquired along the San Pedro and Gila Rivers, and from Salt River and Tonto Creek inlets to Roosevelt Lake in southern Arizona. The satellite model uses a logistic regression equation to divide riparian vegetation into a continuous range of probabilities extending from almost 0 to 99 percent, with higher probabilities most likely to contain a flycatcher territory. The model has been successfully tested at multiple locations, including Alamo Lake, Arizona (Hatten and Paradzick, 2003), and the Rio Grande River, New Mexico (Hatten and Sogge, 2007). In each case, the satellite model performed within expectations by identifying riparian areas with the highest densities of flycatcher territories. Importantly, the satellite model explained 79 percent of the fluctuation in the flycatcher breeding population at Roosevelt Lake from 1996 to 2005 (Paxton and others, 2007; Hatten and others, 2010). Most recently, the satellite model was used to map predicted breeding habitat across the entire range of the flycatcher in the U.S. (Fig. 2), and to examine the effects of drought (Fig. 3).
Another application of the satellite model was an examination of the effects of tamarisk leaf beetles (Diorhabda spp.), which are affecting flycatcher breeding habitat throughout much of their range (Hatten, 2016). In 2001, tamarisk leaf beetles (hereinafter referred to as “beetle”) were released by the U.S. Department of Agriculture Animal and Plant Health Inspection Service (APHIS) at 10 sites in six States (California, Nevada, Utah, Colorado, Wyoming, and Texas) to control invasive tamarisk (Tamarix spp.) (Bean and others, 2013). Tamarisk, which is an introduced phreatophyte and a common nesting substrate for flycatchers and other birds (Sogge and others, 2008; Paxton and others, 2011), spread rapidly following its release over a century ago and is now a dominant riparian species throughout the West (Chew, 2013). Feeding by the beetle larvae defoliates the tamarisk during the growing season and reduces plant vigor, sometimes resulting in plant mortality within 5 years (Hultine and others, 2009, 2015). Since their introduction, beetles have spread naturally into most drainages of the upper Colorado River Basin (Jamison and others, 2015), southern Utah and Nevada, and the main stem lower Colorado River in Arizona (Fig. 4). The satellite model was used to identify areas along the Virgin River that were heavily impacted by the beetle (Fig 5), and to simulate what may occur should the beetle arrive along focal river reaches, such as the upper Gila River (Fig. 6).
The FWS and APHIS requested a web application that can locate, map, and monitor potential flycatcher breeding habitat throughout its range, including areas not designated as critical habitat. Most flycatcher habitat is inherently dynamic, with individual riparian patches subject to cycles of creation, growth, and loss because of drought, flooding, fire, and other disturbances. Former breeding patches can lose suitability quickly, whereas new habitat can develop in a few years, especially in reservoir drawdown zones (Paxton and others, 2007). Because the distribution and extent of flycatcher breeding habitat changes over time, an accurate understanding and assessment of current habitat suitability requires up-to-date information on vegetation characteristics and other variables associated with occupied sites. This web mapping application (Southwestern Willow Flycatcher Habitat Viewer) was developed to meet the needs of government and nongovernmental organizations by providing maps of predicted flycatcher breeding habitat throughout their range.
Bean, D.W., T. Dudley, and K. Huletine. 2013. Bring on the beetles! - The history and impact of tamarisk biological control, in Sher, A., and Quigley, M.F., eds., Tamarix: A case study of ecological change in the American West: New York, Oxford University Press, p. 377-403. DOI: 10.1093/acprof:osobl/9780199898206.003.0022
Chew, M.K. 2013. Tamarisk introduction, naturalization, and control in the United States, 1818–1952, in Sher, A., and Quigley, M.F., eds., Tamarix: A case study of ecological change in the American West; New York, Oxford University Press, p. 269-286. DOI: 10.1093/acprof:osobl/9780199898206.003.0016
Durst, S.L., M.K. Sogge, S.D. Stump, H.A Walker, B.E. Kus, and S.J. Sferra. 2008. Southwestern willow flycatcher breeding sites and territory summary -2007: U.S. Geological Survey Open-File Report 2008-1303, DOI: 10.3133/ofr20081303
Hatten, J.R., and C.E. Paradzick. 2003. A multiscaled model of southwestern willow flycatcher breeding habitat: Journal of Wildlife Management, 67: 774-788. DOI: 10.2307/3802685
Hatten, J.R., E.H. Paxton, and M.K. Sogge. 2010. Modeling the dynamic habitat and breeding population of Southwestern willow flycatcher: Ecological Modelling, 221: 1674-1686. DOI: 10.1016/j.ecolmodel.2010.03.026
Hatten, J.R., and M.K. Sogge. 2007. Using a remote sensing/GIS model to predict Southwestern willow flycatcher breeding habitat along the Rio Grande, New Mexico: U.S. Geological Survey Open-File Report 2007-1207. DOI: 10.3133/ofr20071207
Hultine, K.R., J. Belnap, C. van Riper, III., J.R. Ehleringer, P.E. Dennison, M.E. Lee, P.E. Nagler, K.A. Snyder, S.M. Uselman, and J.B. West. 2009. Tamarisk biocontrol in the Western United States - Ecological and societal implications: Frontiers in Ecology and the Environment, 8(9): 467-474. DOI: 10.1890/090031.
Hultine, K.R., T.L. Dudley, D.F. Koepke, D.W. Bean, E.P. Glenn, and A.M. Lambert. 2015. Patterns of herbivory-induced mortality of a dominant non-native tree/shrub (Tamarix spp.) in a Southwestern US watershed: Biological Invasions, 17: 1729-1742. DOI: 10.1007/s10530-014-0829-4.
Paxton, E.H., M.K. Sogge, S.L. Durst, T.C. Theimer, and J.R. Hatten. 2007. Chapter 6: Spatial Modeling: Pages 97-124 in The ecology of the Southwestern willow flycatcher in central Arizona - A 10-year synthesis report: U.S. Geological Survey Open-File Report 2007-1381. DOI: 10.3133/ofr20071381
Paxton, E.H., T.C. Theimer, and M.K. Sogge. 2011. Tamarisk biocontrol using tamarisk beetles: Potential consequences for riparian birds in the Southwestern United States: The Condor, 113(2): 255-265. DOI: 10.1525/cond.2011.090226
Sogge, M.K., S.J. Sferra, and E.H. Paxton. 2008. Tamarix as habitat for birds - Implications for riparian restoration in the Southwestern United States: Restoration Ecology: 16(1): 146-154. DOI: 10.1111/j.1526-100X.2008.00357.x
U.S. Fish and Wildlife Service, 1995, Final rule determining endangered status for the Southwestern willow flycatcher: Federal Register, 60 FR 10694, Vol. 60, No. 38, p. 10694–10715.
U.S. Fish and Wildlife Service, 2002, U.S. Fish and Wildlife Service. 2002. Southwestern Willow Flycatcher Recovery Plan. Albuquerque, New Mexico. i-ix + 210 pp., Appendices A-O.
U.S. Fish and Wildlife Service. 2013. Endangered and threatened wildlife and plants; Designation of critical habitat for Southwestern Willow Flycatcher; Final rule. Federal Register, 50 CFR Part 17, 78(2): 344-534.
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The Flycatcher Habitat Viewer was developed to meet the needs of organizations by providing maps of predicted flycatcher breeding habitat throughout its range. Maps are provided from 2013 to present and cover 57 satellite scenes. Maps identify predicted flycatcher habitat based upon the amount of green vegetation within a 120-m radius of each cell, and the size of floodplain within a 360-m radius.
Figure 4. Yearly Distribution (2007-2019) of Tamarisk Beetle (Diorhabda spp.). Annual tamarisk beetle distribution map. Provided by RiversEdge West. 2020. Used with permission from Ben Bloodgood, Program Coordinator.
Figure 6. Map showing changes in predicted flycatcher habitat along the upper Gila River after conducting a tamarisk leaf beetle-impact simulation. The upper Gila River was divided into nine zones in order to quantify changes. A satellite model was used to predict flycatcher habitat at a 40-percent probability threshold.
Figure 5. Map showing changes in predicted flycatcher habitat along the lower Virgin River, Nevada and Arizona, 2010–2015, as determined from a satellite model at a 40-percent probability threshold.
Map showing relative changes in predicted flycatcher habitat, as determined from a satellite model at a 40-percent probability threshold, Southwestern United States, 2013–15.
Map showing area of predicted flycatcher breeding habitat (averaged across 2013–15) at all elevations in 6,521 U.S. Geological Survey 7.5-minute quadrangles, Southwestern United States. Only areas within a prescribed distance of streams and greater than stream-order 3, or within 1 kilometer of a lake or reservoir, were included in this analysis.
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