Avian Migration within the Lake Superio Coastal Region of Minnesota

Abstract

The survey approach used in this study has proven to be exceptionally productive for studying migratory movements and stopover habitat use. Visual methods of studying migratory movements are useful where detailed observations or large sample sizes are limited using other methods, as is the case along the north shore of Lake Superior. The topography of the region limits the use of radar to detect diurnal movement or nocturnal stopover use because the ridgelines block radar beams from the primary Doppler radar unit in Duluth. The methods utilized for this study can be tailored to any region where a more detailed understanding of the migratory pathways is desired. A series of vantage points with a wide view of the landscape and transect surveys through various landscape and habitat give a more detailed picture of a migration corridor. This information can be especially useful in siting new tower and wind power developments. Future work with tracking individual raptor species will likely need to rely on satellite transmitters that do not rely on individuals attempting to track individuals through heavily wooded areas with few roads and considerable topography. Several sets of guidelines on the construction of new wind power developments have been developed to minimize impacts on birds. A common thread among these guidelines is the importance of identifying potential conflicts, and to avoid placing development in areas highly important to birds, including migratory pathways (US Fish and Wildlife Service 2012). The results of this and future studies can be used in combination with guidelines that are currently evolving. Using the methods described here, regional maps of migratory pathways can be produced and used to identify the areas that are the most sensitive to development. With the increasing popularity of wind power, the cumulative impacts on birds are of immediate conservation concern, considering direct mortality resulting from collisions has been documented at wind farms (Smallwood and Thelander 2008). It is vital that migratory pathways be identified in detail over large regions to avoid cumulative negative effects on migrating birds. When we considered the topography of the region, it appears that at least for migration raptors, the first two major ridgelines along the shore act as leading lines, concentrating these birds along these ridgelines and along the shore. In addition, migratory songbirds appear to be targeting these ridgelines for stopovers as well. Wind energy feasibility studies have identified such ridgelines as having a potential for wind turbine development (Mageau et al. 2008). In this context, it is crucial that we understand the flight behaviors and stopover habitats of birds that migrate along the north shore of Lake Superior. Proper wind turbine and tower siting within this migration corridor will help to preserve one of the largest migrations in the Midwest and among the largest in the US.