An adaptive approach to managing gull predation at

seabird restoration sites in Maine

 



       
At seabird restoration sites in the Gulf of Maine, depredation of tern (Sterna spp.) offspring and displacement of adults from preferred breeding grounds have been used to justify nest destruction, harassment, and lethal control of gulls (Larus spp.).  Despite widespread control, few studies have quantified gull predation or examined the predatory behavior of gulls at these sites.  In addition, the focus on tern restoration may be detrimental to co-nesting species like the Common Eider (Somateria mollissima), promoting opportunistic gull predation due to frequent disturbance by managers.  This study aims to: i) document gull-seabird interactions, ii) evaluate the effectiveness of current predator control practices, iii) explore non-lethal control alternatives using knowledge of predator behavior and ecology, and ultimately, iv) direct future management policies. 

 

Tern and eider productivity was monitored and daily predation watches were performed at two seabird sanctuaries on the Maine coast.  In 2003 and 2004 at Eastern Egg Rock (43˚52’N, 69˚23’W), less than five percent of all gulls residing on the island were predatory.  Adult Herring (L. argentatus) and Great Black-backed (L. marinus) gulls were the principal predators, specializing on tern offspring and maintaining feeding territories within the colony.  Common Tern (S. hirundo) chick survival varied according to hatch order, within-season temporal variation, daily chick age, minimum daytime visibility, and nest location.  In 2004, eider duckling survival on Stratton Island (43˚31’N, 70˚19’W) was severely limited by opportunistic, group gull attacks. Plans for 2005 will emphasize non-lethal mitigation of gull predation at both sites.

 

Christina Donehower
 

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