Tidal marsh bird conservation in the Northeast USA
Date
2015
Authors
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Publisher
University of Delaware
Abstract
Conservation of tidal marsh birds is a high priority in the United States in light of continued habitat loss from anthropogenic impacts, including climate change. The north Atlantic coast of the U.S. is considered a hotspot for accelerated sea level rise, where rates are increasing three to four times faster than the global average. Increased inundation and coastal storm severity and frequency affect tidal marsh habitat quantity and quality and threaten tidal marsh bird populations with rapid declines or extinction. Tidal marsh bird distributions and abundance are relatively unknown, but are critical for developing effective, novel conservation strategies to increase the likelihood of species persistence. I developed a regional monitoring framework to assess the status of the tidal marsh bird community breeding in the Northeast U.S. (Maine to Virginia), and derived a conservation strategy for the state of Delaware. I sampled 1,780 locations during the 2011 - 2012 breeding seasons to estimate species distribution and abundance in tidal marsh habitat patches for five specialist birds: Clapper Rail ( Rallus crepitans ), Willet (Tringa semipalmata ), Nelson's Sparrow (Ammodramus nelsoni ), Saltmarsh Sparrow (A. caudacutus ), and Seaside Sparrow (A. maritimus ). I used the survey estimates to develop Bayesian Network models to predict distribution and abundance in un-sampled habitat patches as a function of patch covariates. Overall, I found the prevalence of Nelson's Sparrow was similar in Coastal Maine and Cape Cod - Casco Bay and the four other species were most common in patches in Long Island (Saltmarsh and Seaside Sparrows), Delaware Bay (Clapper Rail), and Coastal Delmarva (Willet). I estimated 109,758 (±48,505 95% CI) Clapper Rails; 111,021 (±41,566) Willets; 6,640 (±2,750) Nelson's Sparrows; 60,058 (±19,829) Saltmarsh Sparrows; and 234,542 (±119,419) Seaside Sparrows in the Northeast. In Delaware, I used an optimization algorithm to determine the most favorable, yet cost-effective, unprotected tidal marsh parcels for bird conservation; however, greater than 95% of the marsh area on the selected parcels was inundated under all sea level rise scenarios evaluated. Agricultural land was the greatest remaining land cover type, highlighting the need to assess the potential for marsh transgression on adjacent lands. The monitoring framework, baseline species assessments, and modeling approaches presented here, can be incorporated into an adaptive management tool to guide complex decision-making for tidal marsh habitat and bird populations in an increasingly changing landscape.