Scientists studying long-term response of birds in Minnesota to forest management

Young forests are important as nesting habitat for many breeding birds and are a source of food and cover for many young birds once they leave the nest.  However, for many reasons, the extent of young forest in much of eastern North America has been declining. This has caused many scientists to identify conservation of bird species associated with young forests as a priority and to ask whether forest harvesting can contribute to conservation of these species.

Recently, the University of Minnesota–Duluth, UPM-Blandin Paper Company, Potlatch Corporation, and NCASI have been collaborating on a study to document long-term changes in breeding bird communities in response to forest harvest.  The study is being led by Dr. Alexis R. Grinde and Dr. Gerald J. Niemi of the Natural Resources Research Institute, University of Minnesota–Duluth.

The investigators are sampling birds in several large plots (each 1 mile2 or 640 acres) in managed forests in Minnesota.  The investigators established the large plots in the 1990s, when the plots were dominated by mature forest, and sampled breeding birds over four breeding seasons (1994-1997). Since that time, the large forest plots have experienced varying degrees of harvesting, which provides a unique opportunity for a before-and-after study of changes in breeding bird composition and habitat use.

With support from NCASI, UPM-Blandin, and Potlatch, the investigators sampled breeding bird communities in 2013–2017 on a large 1-mile2 plot on land owned by UPM-Blandin.  In the early 2000s, more than 75% of this plot was experimentally harvested to mimic fire disturbance. As a result, the plot is currently a mosaic of young forest intermixed with other forest age classes and other cover types, such as open meadows and wetlands.

As expected, the proportion of individual breeding birds associated with young forests had increased since 1994-1997 and the proportion associated with mature deciduous forests had declined.  A surprising finding, however, was the larger-than-expected abundance during 2013–2017 of five bird species identified by Audubon Minnesota as “Stewardship Birds of Minnesota,” specifically the Golden-winged Warbler, Chestnut-sided Warbler, Nashville Warbler, Rose-breasted Grosbeak, and Veery. In fact, the UPM-Blandin plot has one of the highest concentrations of Golden-winged Warblers ever reported. This is important, because the Golden-winged Warbler is one the most rapidly declining songbirds in North America.

Over the coming year, the investigators will be sampling breeding birds again on this large forest block to assess Golden-winged Warbler abundance and spatial distribution.  They also will be preparing publications describing breeding bird community responses to forest harvesting and succession over 20 – 25 years using data gathered on five large forest plots, including the plot on lands owned by UPM-Blandin. 

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