May 20, 2016
Experimenting with Predator Exclosures at Wilson’s Plover Nests
Posted by: Jeanne Christie
Numerous species of shorebirds across the globe are currently experiencing population declines. For beach nesting shorebirds, increased pressure from predators, development, and recreation are the primary reasons for the decline in nesting success at breeding sites. These disturbances ultimately led to a 30 year declining population trend, and listing of Wilson’s plover, Charadrius wilsonia, as “threatened” in the state of Georgia.
LSSI’s Ecological Technician and University of Georgia graduate student, Lauren Gingerella, banding Wilson’s plover chicks within a predator exclosure
Little St. Simons Island (LSSI) is recognized as a Western Hemisphere Shorebird Reserve Network (WHSRN) site for it’s healthy, untouched coastline that is vital to the survival of numerous shorebird species. The Altamaha River deposits sediment and nutrients that benefit breeding, wintering and migrating shorebirds. LSSI’s rapidly growing shoreline provides excellent habitat for nesting birds, like Wilson’s plovers, American oystercatchers, and least terns. In recent years, LSSI had some of the highest nesting concentrations of plovers and oystercatchers in Georgia. Abby Sterling recorded 165 Wilson’s plover nests in 2015 while collecting data for her Ph.D. research, which is believed to be one of the highest counts in the southeast.
With funding from the National Fish and Wildlife Foundation, I am currently experimenting with predator exclosures at Wilson’s plover nests to try to increase nest survival and the number of chicks produced. Little St. Simons Island is the ideal location for this project due to the high density of nesting plovers. Predator exclosures have been used to protect piping plover nests, and has shown to increase nest success. In Michigan, consistent use of exclosures and symbolic fencing increased hatching success from 37% to 72% between 1984 and 1999. In addition, exclosures have increased reproductive success with other shorebirds, including pectoral sandpipers, killdeer, northern lapwings, and southern dunlin.
A predator exclosure that is set-up around a Wilson’s plover nest
Predator exclosures are constructed from 2×4 welded wire that is formed into a 10 foot diameter circle. The fencing is placed with the nest directly in the center of the exclosure. Wilson’s plovers can freely walk through the openings in the wire fence, unlike predators such as raccoons and coyotes. Mesh is affixed to the top of the exclosure so crows and grackles are unable to fly in and predate the nest. Each exclosure is buried at least 8 inches into the sand, and supported with five wooden posts. A trail camera is placed at each exclosed nest to monitor for predators that may show more attention towards exclosures and harass the adults.
Freshly hatched and banded Wilson’s plover chicks from a nest within an exclosure
I am color banding chicks that hatch from both exclosed and control nests (nests with no exclosure). Each chick is marked with a unique color combination. When a banded chick is resighted, I know exactly which individual bird it is from its color bands. By banding and resighting chicks, I can determine the number of chicks that successfully fledge (fly). The threat of predation significantly drops once a chick fledges.
A banded chick from a control nest
A banded chick from an exclosed nest
Weight and tarsus measurements are recorded for every banded chick
This project has the opportunity to benefit ecologists on other barrier islands monitoring Wilson’s plovers and managing predators. If predator exclosures are proven successful with Wilson’s plovers then they can be used to increase hatch success at other breeding locations. If you spot a banded Wilson’s plover while visiting Little St. Simons Island, please try to snap a photo and report your sighting to LSSI staff.