To document the value of Maine Coastal Islands National Wildlife Refuge lands to migrating birds, refuge biologists have joined forces with other partners in the newly established Northeast Regional Migration Monitoring Network (Network). The biologists are working with others from the National Park Service, the University of Maine and AcadiaUniversity in Nova Scotia, to research where and when migrating songbirds and other bird species fly over the region’s extensive and coastal areas.
The Network team has found that the Gulf of Maine is a major corridor for migrating birds in both spring and fall.
Observing migrating birds during daylight can be done through systematic visual surveys. But, most migrants make their way under the relative safety of the night when the winds tend to be calmer and the risk of predation is low. This makes it challenging for researchers to document the kinds and numbers of birds on the move, and when and where they pass through the region. The Network’s approach to studying patterns of migration in the Gulf of Maine uses methods to not only look at broad-scale movements of birds with marine surveillance radar and visual surveys, but to also use banding, orientation release tests, and radio-telemetry as ways to study the migratory behavior of individuals.
Many migrating birds make species-specific calls, that, when recorded at different locations along the region, can provide important information about the timing and flight paths of certain species. The Network team has placed sensitive microphones across the region to record the flight calls of birds as they fly overheard. This ‘passive acoustic’ survey method complements information gleaned from the radar by helping to identify what the radar detects. The radar, by its ability to document the density of birds migrating overhead and the birds’ flight altitude and direction, reveals which direction birds are heading as they pass by.
The banding program run by the Maine Coastal Islands National Wildlife Refuge Complex, University of Maine, and National Audubon last year revealed that as many as a half million or more songbirds fly over and coastal areas just in the mid-coast region alone during autumn. Spring migration studies at Metinic this year showed that migrating songbirds also use these same areas on their way north. Such banding efforts not only reveal which species migrate through the area but, by assessing energetic condition, can also tell how healthy the birds are.
Stable isotope markers incorporated in small feather samples taken from the birds in autumn are being analyzed by collaborators with the Canadian Wildlife Service-Environment Canada to determine where individuals have bred or were born. Samples taken in spring can provide information about where they spent the winter.
Migratory decisions at the scale of the individual bird are also being closely examined. Because songbirds are too small for most tracking methods, studying their movements is more challenging. But, researchers from Acadia University are applying novel technological advances to the program. In addition to operating radar units at specific sites, they are deploying tiny transmitters, developed by Lotek Wireless, Inc., on small songbirds in southwestern Nova Scotia. Birds carrying these tiny transmitters can be detected by an array of receivers set up along the coast of Nova Scotia and Maine telling the researchers the flight path an individual bird has taken as the move through the region. Already, the flight and stopover movements and rate of migration of free-flying individual songbirds have been documented for the first time in the Gulf of Maine.
The majority of terrestrial bird species moving through the Gulf of Maine region breed in the boreal forests, taiga, and tundra and these regions are experiencing the greatest threat from climate change climate change
Climate change includes both global warming driven by human-induced emissions of greenhouse gases and the resulting large-scale shifts in weather patterns. Though there have been previous periods of climatic change, since the mid-20th century humans have had an unprecedented impact on Earth's climate system and caused change on a global scale.
Learn more about climate change and habitat destruction. To look at patterns of migration and the relationships between migrants and available habitats requires incorporating landscape scale patterns with fine-scale decisions made by individuals. Partners in the Northeast Regional Migration Monitoring Network are turning eyes and ears to the skies to better understand the needs of migrants and to determine how to best manage breeding and stopover habitats necessary to support birds that breed in or move through the region.
