West Gulf Coast Mottled Duck Nesting (Southeast Blueprint Indicator)

Reason for Selection The mottled duck is a non-migratory waterfowl species endemic to the Gulf coast that relies on a unique mix of coastal marshes and nearby grassland habitat for foraging, nesting, and raising young. The West Gulf Coast mottled duck population has declined significantly since the mid-1990s due to habitat loss from urban growth, agricultural development, saltwater intrusion, and invasive species (Moon et al. 2021, Krainyk et al. 2019, Moon et al. 2021). Mottled ducks are considered an indicator of coastal marsh health and function (Moon et al. 2015), and other indicators in the Blueprint were not capturing the important ecological role of grassland habitats near wetlands in the Western Gulf Coast. Input Data * [Spatially Explicit Decision Support Tool for Guiding Habitat Conservation for Western Gulf Coast Mottled Ducks]: Currently suitable nesting habitat Because mottled ducks use coastal marsh and agricultural landscapes somewhat differently, this model identified suitable nesting habitat in two different zones: agricultural and coastal. In agricultural areas, nesting cover is usually found in “fallow fields, low-intensity grazing systems, hay fields, native prairies, and other grasslands” with less than 30% woody cover (Krainyk et al. 2019). Here, the model defined suitable nesting habitat as patches of suitable agricultural or grassland land cover that are at least 40 acres in size, with a 0.025 m/sq m edge-to-interior ratio, and no more than a mile from currently suitable brood-rearing habitat. In coastal marshes, “mottled ducks prefer nesting habitat characterized by tall, dense stands of grass, usually located in elevated sites within 150 meters of water” or “on narrow ridges or levees that are surrounded by marsh” (Krainyk et al. 2019). Here, the model defined suitable nesting habitat as patches of suitable agricultural, grassland, or wetland land cover that are at least 40 acres in size and no more than a mile from currently suitable brood-rearing habitat (very similar to the parameters used in the agricultural zone, but with the addition of wetland land cover and removal of the edge-to-interior ratio requirement). * MODU_range_byInitiaveArea (contact Blair Tirpak for access at [blair_tirpak@fws.gov]) * [Base Blueprint 2022 extent] * [Southeast Blueprint 2023 extent] Mapping Steps * Divide the currently suitable nesting habitat layer into 10 equal area classes using the Slice tool in ArcPro. * Create an extent raster with a value of 0 from the MODU_range_byInitiativeArea shapefile. Zero values are intended to help users better understand the extent of this indicator and make it perform better in online tools. * Mosaic the 10-class raster with the extent raster. * Reclassify the resulting value field into the final indicator values seen below. * Clip to the spatial extent of Base Blueprint 2022. * As a final step, clip to the spatial extent of Southeast Blueprint 2023. Note: For more details on the mapping steps, code used to create this layer is available in the [Southeast Blueprint Data Download] under > 6_Code. Final indicator values Indicator values are assigned as follows: 10 = 90th-100th percentile of suitable mottled duck nesting habitat 9 = 80th-90th percentile of suitable mottled duck nesting habitat 8 = 70th-80th percentile of suitable mottled duck nesting habitat 7 = 60th-70th percentile of suitable mottled duck nesting habitat 6 = 50th-60th percentile of suitable mottled duck nesting habitat 5 = 40th-50th percentile of suitable mottled duck nesting habitat 4 = 30th-40th percentile of suitable mottled duck nesting habitat 3 = 20th-30th percentile of suitable mottled duck nesting habitat 2 = 10th-20th percentile of suitable mottled duck nesting habitat 1 = 0-10th percentile of suitable mottled duck nesting habitat 0 = Not identified as suitable mottled duck nesting habitat (within TX and LA) Known Issues * This indicator represents a perspective on grasslands through the lens of a single species that requires grasslands to be in proximity to low salinity wetlands. As a result, it potentially excludes some larger blocks of intact grasslands. * Mottled ducks also nest within some emergent coastal marshes; therefore, this indicator might include significant contiguous blocks of emergent wetlands in some areas, especially where the salinities don’t exceed intermediate ranges. * This indicator defines suitability for mottled duck based solely on landscape context and does not consider grassland condition (e.g., it does not differentiate overgrazed areas, grasslands dominated by exotics, etc.). Disclaimer: Comparing with Older Indicator Versions There are numerous problems with using Southeast Blueprint indicators for change analysis. Please consult Blueprint staff if you would like to do this (email [hilary_morris@fws.gov]). Literature Cited Krainyk, Anastasia and Bart M. Ballard. 2014. Decision Support Tool: Prioritization of Mottled Duck (Anas fulvigula) Habitat for Conservation and Management in the Western Gulf Coast. Final report. [[https://www.sciencebase.gov/catalog/item/547cb566e4b0bdc51793037c]]. Krainyk, Anastasia, B. Ballard, M.G. Brasher, B.C. Wilson, M. W. Parr, C. K. Edwards. Decision support tool: Mottled duck habitat management and conservation in the Western Gulf Coast. Journal of Environmental Management, v. 203, p43-52. [[https://doi.org/10.1016/j.jenvman.2018.09.054]]. Moon, Jena, D. Haukos, W. Conway. 2015. Mottled Duck (Anas fulvigula) Movements in the Texas Chenier Plain Region. Journal of the Southeastern Association of Fish and Wildlife Agencies 2:255-261. [[https://seafwa.org/sites/default/files/journal-articles/37%252520Moon%252520et%252520al%252520255-261.pdf]]. Moon, J.A., Haukos, D.A. and Conway, W.C. (2017), Seasonal survival of adult female mottled ducks. Jour. Wild. Mgmt., 81: 461-469. [[https://doi.org/10.1002/jwmg.21221]]. Moon, J.A. and S.E. Lehnen, K.L. Metzger, M.A. Squires, M.G. Brasher, B.C. Wilson, W.C. Conway, D.A. Haukos, B.E. Davis, F.C. Rohwer, E.M. Wehland, B.M. Ballard. Projected impact of sea-level rise and urbanization on mottled duck (Anas fulvigula) habitat along the Gulf Coast of Louisiana and Texas through 2100. Ecological Indicators, Volume 132, 2021, 108276, ISSN 1470-160X, [[https://doi.org/10.1016/j.ecolind.2021.108276]]. Ringelman, K. M., Bonczek, E. S., Marty, J. R., Booth, A. R., & Dopkin, A. L. (2021). Survival of western Gulf Coast Mottled Ducks (Anas fulvigula) in the path of a Category 4 hurricane. Ecology and Evolution, 11, 15477– 15483. [[https://doi.org/10.1002/ece3.8276]].