If you flood it, they will come: auantifying waterbird response to the Migratory Bird Habitat Initiative
Sieges, Mason L.
University of Delaware
In response to the Deepwater Horizon oil spill, the Natural Resources Conservation Service implemented the Migratory Bird Habitat Initiative (MBHI) in fall 2010 to provide temporary wetland habitat for migrating and wintering waterfowl, shorebirds, and other waterbirds that might be impacted by oiled wetlands along the northern Gulf of Mexico. Using weather surveillance radar, I conducted regional assessments of bird response to shallow-water flooding on privately-owned agricultural lands within the Mississippi Alluvial Valley (MAV) and the West Gulf Coastal Plain (WGCP) from fall 2010 through spring 2011. I also conducted a more focused analysis on MBHI sites in Louisiana where different management regimes were directed at specific waterbird taxa during different seasons and management was conducted over multiple years. Specifically, mudflat and shallow water habitats were created to benefit migrating waterfowl and shorebirds in the fall and spring while fields were flooded to greater depths in winter to supply wintering waterfowl with food and cover. I detected increases in diurnal bird density at the onset of evening flights over managed sites relative to the two prior (unmanaged) years as well as compared to concurrent bird densities over non-flooded agricultural lands in the surrounding landscape. Changes in bird density matched seasonal shifts in waterbird distributions and abundance with the greatest observed densities corresponding to the arrival of wintering waterfowl in December. Record flooding in the two years prior to implementation of the MBHI coupled with a region-wide drought during management years complicated the quantification of changes in remotely-sensed soil wetness on sites. Specifically in Louisiana, bird use of MBHI sites was greatest just after the onset of flooding on mudflat sites in the fall. Across regions and seasons, bird response was generally related to the land cover composition of the site and the surrounding landscape (i.e., amount of emergent marsh and agriculture) and/or the proximity of the sites to high density bird concentration areas (e.g., large waterfowl populations on refuge lands such as Laccassine NWR in Louisiana). The relationship that bird density had with landscape variables differed depending on region and season. In general, I detected greater increases in relative bird use at sites in close to areas of high bird density during winter in both the MAV and WGCP. Bird density was also greater during winter at sites with more emergent marsh within sites and in the surrounding landscape. By enrolling lands located near high density bird areas and within existing wetland complexes, future conservation programs could maximize bird use of managed wetlands. Weather radar observations suggest that waterbirds used temporary wetland habitat provided by the MBHI within the Mississippi Alluvial Valley and the West Gulf Coastal Plain regions in the wake of a major environmental disaster.