Ask SIB: What happens if Deveaux disappears?

After watching the replay of Felicia Sanders presentation on shorebird migration, Andy Allen asked: I just watched the shorebird presentation replay. The importance of Deveaux Bank to migratory and also local breeding birds is enormous. However Deveaux Bank is not a stable island. When we first bought here forty years ago it was actually two small islands with a significant channel between them. A few years later we came down and discovered it was gone-just ocean. A local resident said this happens every so often when a nor’easter comes down and scours out the sand, taking it elsewhere. We have watched the re-emergence of Deveaux over the years and hopefully it will achieve some permanence. My question for the DNR presenter would be, “What do all the birds do if suddenly Deveaux is gone?”

Felicia kindly provided this response:

The simple answer is we don’t know! Maina Handmaker, the PHD student at USC, is using high resolution location data that we are getting from the GPS tags on select Whimbrel to investigate Whimbrel movement and migration. She is looking at how site faithful Whimbrel are to Deveaux and the characteristics of the island that make Deveaux an ideal nocturnal roost for thousands of Whimbrel. Hudsonian Whimbrel are experiencing a steep decline: peak numbers in the Atlantic flyway decreased nearly 50% over a 15-year period beginning in the early 1990s (4.2% per year). There are many possible causes for the decline but surveys finding very few nocturnal roosts suggests that suitable places to sleep may contribute to the observed decline.

The limited number of Whimbrel roosts may be the result of human alteration of coastal areas. Shifting islands and shoals, such as Deveaux, form naturally at river mouths from sediment deposits. However, human activities, such as the placement of physical structures to protect against coastal erosion, mining
intertidal sand for beach renourishment projects, and dredging shipping channels can alter natural shoreline processes. Much of the Atlantic coast of the United States now has hard structures that limit coastal migration and the natural accretion of islands. This has important implications for Deveaux: we
first discovered large numbers of Whimbrel using Deveaux in 2014 but are unsure how long the island has been an important roost site. Deveaux was known to be important for nesting waterbirds in the 1930s, then disappeared after Hurricane David in 1979. To mitigate the potential ephemerality of the island, identifying or creating a network of alternative roost sites is therefore a necessity.

You may have heard about the renourishing or building of Crab Bank in Charleston Harbor last November. The island is 80 plus acres at low tide. The Army Corps made the island from sand taken from the deepening project of Charleston Harbor. The island is so large, Whimbrel may be able to use it as a
nocturnal roost. Opportunities such as this one may help to create alternative roost sites when islands used by shorebirds disappear in the natural cycle of coastal movement that includes erosion.

For information about the Whimbrel roost see the website, Discovery at Deveaux, especially the manuscript under the “Press” link at the top right.

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