Sheep Grazing as Habitat Management on Eastern Brothers Island USFWS photo by Sara Williams

Prescribed Fire for Habitat Management on Petit Manan Island USFWS photo by Sara Williams

Maine Coastal Islands National Wildlife Refuge implemented the first of a three-year Adaptive Management Study to determine the best management practices for enhancing Arctic and Common tern habitat on three refuge islands in the Gulf of Maine.  The Refuge owns six of the ten islands in Maine that support more than 94% of breeding Arctic and common terns, laughing gulls, and Atlantic puffins. The success and perpetuation of many of these colonies depends upon active predator control and annual habitat management using techniques such as mowing, prescribed fire, and sheep grazing.  The goal of treatments is to cost effectively create low vegetation communities that stay low during the tern breeding season.

Determining the efficacy of a management strategy can be challenging on these remote offshore islands.  In addition to the chosen technique, the season in which the treatment is applied, island topography, available moisture, storm events, soil type, soil depth, and even breeding bird densities influence habitat conditions.  Many of these inconsistent and unpredictable environmental variables are either not well documented or their relationship to vegetation communities is not well understood.  The Refuge sought assistance in designing a non-invasive habitat monitoring program for tern colonies that synthesizes observational knowledge with standardized data to deepen our ecological understanding of these systems.

Through a new Region 3 and Region 5 Biological Management Team initiative with USGS, the Refuge received funding to conduct an Adaptive Management Study, kicked off by a two day consultation last November with experts in the fields of seabird research and management, soil science, botany, and Maine island ecology.  This February, refuge staff and USGS statisticians developed a predictive model for vegetation management using the collective knowledge of refuge staff and experts.  Our predictions for the response of vegetation to management will be updated after three years of standardized treatments and data collection. 

This spring and summer, we implemented prescribed fire, grazing, mowing or a combination of techniques on Petit Manan, Metinic, and Eastern Brothers Island and rapidly sampled vegetation during three time periods: tern arrival, the peak of nest incubation, and chick fledging.  Tracking daily weather conditions and completing soils investigations will also help us interpret differences between seasons or between islands. 

We hope this study will provide us with an adaptive tool to make informed management decisions by accurately predicting the habitat quality produced by different management techniques and the effort required to obtain and maintain suitable tern habitat.  In order to reach the Refuge's Comprehensive Conservation Plan seabird conservation objectives (2005), four additional islands will be restored and managed over the next 15 years. The model developed by this Adaptive Management study will be utilized to select appropriate islands for future seabird restoration and ultimately increase our capacity to manage multiple islands.