Poplar Island, Chesapeake Bay, Maryland: Exclusion of herring gulls (Larus argentatus) and great black-backed gulls (Larus marinus) Using Overhead Parallel Lines

Abstract

Poplar Island is a small island (1,700 acres) located in the mid Chesapeake Bay region in Talbot County, Maryland. Poplar Island has experienced severe erosion due to rising sea levels and was once deteriorated to only 5 acres of land. With the help of the U.S. Army Corps of Engineers and U.S. Fish and Wildlife Service, the Paul S. Sarbanes restoration project on Poplar Island has helped reconstruct Poplar Island using dredged material from the shipping channels in the Chesapeake Bay. The island has been divided into upland forest cells and lowland wetland cells. High vegetation survival rate is crucial to help mitigate the effects of erosion. In the spring of 2016, U.S. Fish and Wildlife Service biologists began to notice that the newly planted grasses within wetland cell 3C were being uprooted and destroyed by wildlife. Closer investigation with the help of game cameras, showed that herring gulls (Larus argentatus), great black-backed gulls (Larus marinus), and Canada geese (Branta canadensis) were causing the vegetation damage. Research into effective control measures to deter gulls and geese led to the possibility of using overhead parallel lines to deter gulls and geese. Overhead parallel lines have been used to deter various species from water sources in the United States, but no definitive distance between lines has been proven the most effective. In order to determine the most effective overhead parallel line system for Poplar Island, three different types of plots were set up (control with no lines, 5-meter intervals, and 10-meter intervals). Surveys were completed 2-3 times a week over the summer of 2017 to determine which distance between lines was most effective in deterring gulls and geese. Statistical analysis showed that the plots with parallel lines at 5-meter and 10-meter intervals were more effective in deterring gulls than the control plots, with the 5-meter plots being slightly more effective than the 10-meter plots in deterring gulls. The results from this small scale experiment can be taken into consideration when implementing overhead parallel lines as a control measure against gulls on a larger scale on other parts of Poplar Island as well as on other islands in the Chesapeake Bay.